Hope the video was helpful! If you need some tools recommendations check below Quality meter to test voltage of capacitors - amzn.to/3x7P5eL High Voltage Discharge Stick amzn.to/3x4BuVt Drivers to use around high voltage - amzn.to/3j8zweN
Question: Blower unit capacitor in my Bryant forced air heater might be bad. So… before I attempt to remove it, how long after cutting off all power to unit, will it take to discharge on its own? An hour? A day? Thanks in advance for your response.
@@john-robert1961 Not sure, but if it was me I would turn it off. Then go measure it with my multimeter. Then I would wait a few minutes and check it with my multimeter again (voltage setting). See if it's discharging on its own and how fast.
@@HTMWorkshop thank you kindly for your rapid response. Naturally, I would turn off the main wall switch that connects to the unit, before even attempting to test anything. I will do the voltmeter test, followed by the capacitor test. I’m glad that I have encountered your video earlier this evening, it’s very informative.
@@john-robert1961 Back in the day, it's amazing how many people went POKING around (INSIDE) those old VACUUM TUBE TV's with a SCREWDRIVER!🤯😁😆😂🤣😂 BEFORE properly discharging the Capacitors! What a SURPRISE they received!😆😂🤣
My trick for those 200V or 400V capacitors is to use a lightbulb with wires soldered to it and just discharge it using the bulb, best to use an old fashion one with wire inside it, really useful when you are dealing with such voltage.
For as long as I can remember, my dad keeps a lightbulb on some wires in his tools, which he uses to test circuit completion when doing house electrical work. Of course he first finds the live phase with a tester, and then checks with the lightbulb to be sure the ground is also connected. Why not use a voltmeter you say? Well he says, "I don't have a third hand to hold it with".
@S Wong it can but only for low current situations! Most LED's can take around 20mA so you do not want to exceed the max current (or else your LED will turn into a fuse - which is not the end of the world since most LED's are cheap but it may fool you into thinking your capacitor is discharged when in reality you just fried the LED).
Electrical burns can definitely hurt. Hope your ok, glad your learning from your mistakes! “The only real mistake is the one from which we learn nothing.” HF
@@HTMWorkshop it still hurts after 1 day and I have a massive boil but I still need to see how to discharge these 450v I work with I repair consoles and they have 2 of these big capacitors I saw something on the internet to connect a light bulb to alligator clips and discharge it that way but I wasnt successfully in riggin something up so I just used the old screw driver but they discharge extremely dangerously in my opinion and I dont want to blow one up in the system.....
@@176cgna Yeah a screwdriver is just releasing the energy very quickly (and that means things can get hot), you need a good high Watt resistor (and decently high resistor, depends on how many Farads you are dealing with and how quick you want to discharge - has to due with time contact of an RC circuit). Most incandescent light bulbs are rated for 60W, and have a pretty low resistance of 120 ohms, so for a 450 V source you are roughly looking at around 3.75 Amps (most bulbs are rated around 0.5 amps). So not a great solution for high voltages. Some places sell high voltage discharge sticks for about twenty bucks if you want a profesional solution. But if you can find a high watt (2 W or greater with a resistance of around 100 kohms, that should work, just may take a while to discharge depending on your capacitors)
@@HTMWorkshop ah ok ima look for that tool I dont care about price and I work with these capacitors enought to warrent the purchase of a professional tool
Great video! I wish they explained things this well when I was in school. They probably did I just didn't get it at the time. Age is not always a bad thing! Thanks for the info.
they cover it indirectly if that is of any constellation. For my CompTIA A+ they said that if you get trained to work on televisions you will be taught how to properly discharge the capacitors, then in electrical they explained the relationship between resistors, capacitors, and time. Then throughout electrical they regularly explain that oftentimes steps often considered not recommended are the safest way to do tasks while implying that shorting a connection is sometimes the case. Never once do they explicitly teach anything about properly discharging a capacitor but by the end you have tons of hints. So for this reason I am very happy to learn the specific recommended process for the first time and as such I would very much like to thank the video author.
I came to send this video to my neighbor. I once saw a dog lick a charged capacitor by mistake while a parent was getting tools to repair an opened microwave. The dog was flung off and hurt pretty bad. It stuck with me. I was walking by this morning when I saw a guy taking a microwave apart. I asked if he discharged the capacitor first. When he said the what now? I told his wife please get him away from it. He will get hurt! I then sent them your video. DAMN People! Come on!
Always cut the trailing ends of strings off when you change them was good advice I was given. 1: So you don't blind someone and 2) They can penetrate electrical equipment!
I really learned a lot from this video and I sincerely thank you. I hope you make a video teaching how to safely discharge a higher voltage capacitor-not necessarily the 2100V type, but the 200V to 400V range might be helpful. For reference regarding the 2K capacitors, it may add perspective for people to realize that the electric chairs used in the electrocution of condemned prisoners typically delivered around 2,000V. Granted, they were higher amperage (7 to 10A) and the charge was delivered for several seconds, but it gives us an idea of the seriousness of 2,000V.
Very good video and explanation, i once thought about touching one of capacitors even though it was only 25v and at that time i didnt know what those things were and well i have to say thank god i didnt touch them and thank god it wasnt a high voltage capacitor (didnt know what was going through my mind at that time xd)
I didn't learn what I wanted from this video but it was strangely very entertaining (I thought this video could teach me the recommended specs for a capacitor dischargwr)
I've been dealing with caps for decades, so I didn't learn anything new from the video, but I was highly impressed with your teaching style, calm and steady and looked like you prepared well. It is obviously aimed towards beginners, and you reduced the topic to its essential elements, and explained them simply. I was hoping to see what you had to say about BIG caps, I worked at a 500 Kilowatt shortwave station. Can't say "my loss" as I enjoyed watching your video. 73deK1WXY
Anything involving high voltage. Current transformers...If the secondary has no load, the secondary voltage can soar to very high voltages. Won''t explain why here, google it. Large batteries...Watch your jewelry. If metal watch band or bracelet shorts out a large amperage battery, you will not be electrocuted, but may get an impression of the jewelry BURNED INTO YOUR WRIST. Can and has happened to people reaching up under the dashboard fiddling with stuff up under there. A ring contacting the battery terminal on the rear of the starter switch melted a friend's wedding ring into his finger, ouch. Any one else got any suggestions?
Thank for the knowledge sir I really appreciate it. One of my relatives son telling about his experience about electronics and then he told us about capacitor thing and tell us how dangerous it can be that's why I am here to gain knowledge.
I use solder wick to discharge or verify discharge if not in circuit. I have a 8 Ohm 10 W resistor (used for ESU testing) I use for board discharges (with jumper wires of course)
🤔Interesting. I have not used solder wick for that application, but I see n no reason not to as long as you are ok with a quick discharge. Nice tip if your doing board work and some handy. The 8 ohm resistor would definitely be a good discharge resistor. Out of curiosity what test are you doing on the ESU with the resistor?
Also, as a note, that resistor is 5 watts which means it can take higher power. (Little resistors are 1/4 W or even 1/8 W. Not sure what surface mounted ones are rated at.)
I have three microwave capacitors rated at 2100V sitting around my house not yet discharged! Just realized I'm lucky to be alive, and that is why I am watching this video.
Usually, they have resistors built in to discharge themselves. But, it's always a bad idea to rely on one point of failure with big caps. Capacitors can also spontaneously develop a charge to do dielectric re-absorption. I personally like to keep them permanently shorted out with alligator clips like that, just in case!
So I have 4 Caps that are in the power supply circuit of a stereo processor. It's 19.5V AC feeding 35V 470uf Caps. I need to replace them as a few have begun to leak. Do I need to worry about discharging them before un-soldering them from the circuit?
20 V is pretty safe, 35 V is still pretty safe but on the edge of possible issues. I personally would not worry but if you want to be extra safe I would just use a screwdriver to discharge them (or some other piece of metal)
Thanks for this this informative video! I need to remove a very old high power xenon lamp igniter and want to do so safely and not get knocked on my butt!
why not use resistor to discharge capacitor that has high voltage if you are holding the ceramic part? what would you suggest to use to discharge over 1,000 volt capacitor when usually equipment insulated for just 1,000? thanks
You definitely can use a resistor but you need to make sure you get one with an appropriate wattage rating. You can reduce the power with a higher ohm resistor but then the higher the resistance the slower the discharge. I would use one of those high voltage discharge sticks I have in the description otherwise you can size out the resistor you need if you have a bunch of high wattage one - but for most people they don't want to bother with doing the calculation
Thanks! What res is recommended and up to what voltage cap? And is it alright to touch the leads of that res when doing that? Also is a discharge pen recommended for higher voltage?
That depends a lot on the situation - for instance do you just want to discharge the capacitor or do you care about keeping the circuit integrity and capacitor working afterwards. A very consdervative basline is around 24 V - I don't mind touching 24 V shorted but if you discharge a 24V cap fast it may damage the circuit around it (depends on the situation). In practically I wouldn't mind discharging a 500 V capacitor if it had a small capacitance and a insulated handle - but that is getting more risky and could easily damage the circuit. It really has to do with your risk tolerance and what your comfortable with but always best o err on the side of safety if you don't have a good grasp on the circuit and your own risk.
Thanks - depends on what type of power the potentiometer can take. The resistance is good - but if you run to much current (at a high voltage.. remember Power = current x voltage) then you may burn up the potentiometer. I would not recommend it for discharging very very high voltage things - but my guess is for most applications it would be just fine since it is just a high resistance - and therefore low current.
Do you have to touch both leads / connections of the capacitor? And the shock happening in what is between the leads? Or is it a matter of charge being able to go to ground? In which case, is only one of the leads actually dangerous (the one with electrons at it's disposal to send out)?
Usually, yes between leads. Touch current is going to be negligent unless one of the leads of the capacitor is already grounded (in which case if you touch the other lead it can still discharge). In other words caps are not by nature grounded but if you connect one lead to ground then the other lead is going to be dangerous (if its at high voltages)
@@HTMWorkshop Thank you! If the wires of 1 resistor are not long enough, could I use 1 wire from 2 different resistors to discharge the capacitor still?
@@grooty6434 Im not exactly sure what you mean - you can use two resistors in series - yes. There must be a path between the leads of the capacitor - what you put in between determines how fast the discharge (based off resistance mainly) - see more info on time constant of caps for how long it will take
Do the microwave capacitors tell you how long it takes to bleed out that voltage once they are unplugged? I'm guessing a few seconds. Still makes me nervous.
I don’t think the manual will tell you...but your probably right. Assuming all is working correctly. Best to unplug, check with a voltmeter then do a quick discharge to be extra safe.
@@raybradshaw8444 It would depend on what kind of wattage the resistors could take. Maybe a 1 MOhm resistor ... but it could take some time to discharge depending on how many farads. Often you see 100 kOhms used in high voltage discharge sticks.
@@HTMWorkshop as a basic sum it took 15sec with a 50kohm (3 R in a sting) tool on 300v, and 30sec with a 100kohm (6 resistors in a sting) on 300v, so dum math says 300secounds with the 100kohm so 5mins for 3000v. i just dont know if my little 100kOhm Tool will handle 3kv and not melt like a icepop, lol
@@raybradshaw8444 It just depends on what the resistor is rated for power wise - is it a high Watt resistor? The higher the resistors the slower the current will move so you can use lower watt resistors (its a tradeoff between power the resistor can handle and time it takes t discharge). You have to check both.
I have read through some of the comments. I have worked around 400 volt lines and higher as a research scientist. Around 400 volts, there is an invisible charge cloud or corona about these lines and devices connected to them. If one is grounded, burns, neurological and brain damage and death can result without direct contact. An kindly older electrician told me this when I was 24 or 25. He saved me injury and death many times over.
Good point - yeah I use to work with 1-10kV and your right (everything even air becomes a conductor at some point and ions can form). I use to do some electrospinning back in the day, and it takes advantage of that very effect.
Thanks for the video. I’m looking for an example that explains what size resistor is needed, or should be used with, the capacity trying to be discharged?
Hmm - I don't exactly have a video on that. I do have a blog that may be helpful here htm-workshop.com/how-to-discharge-capacitors-safely/. Also I know in a couple of the comments for this video I explained some specific resistor choices for caps. The key is understanding the power the resistor can take and how fast you want to discharge the cap. P = IV or V2/R , so don't exceed the power rating of your resistor or you will fry it - also the time it takes is based of the time constact for a capacitive resistor circuit ruclips.net/video/JcrlL8YN6VQ/видео.html. A 10W 1MOhm resistor may be a good place to start but it is very conservative (for most circuits)
Wanted to ask a question in regards to discharging using a ceramic resistor like you did in this video, I noticed when you were discharging you still had part of your finger on the metal bit of the resistor, Is that safe to do so?, Also does it matter what polarity the resistor is to the capacitor?, I'm assuming it doesn't have polarity and doesn't matter which way you discharge it, whether its face down or face up. Lastly do both the legs of the resistor have to make contact with the legs of the capacitor at the same time for discharging? TIA
Resistors do not have polarity and yes both legs of the resistor must touch both legs of the capacitor to discharge. As far as if its safe to have your finger touch the metal part - the answer is maybe but best practice is NOT to touch it. Certain voltages are perfectly safe but if you are not that familiar with safe voltage I would just stay on the safe side.
Good question, depends on how how fast you need to discharge the capacitor. Time constant is a key factor to determine how long it will take, time constant = RC. So if you had a 1 uF capacitor and a 1 MOhm resistor it would take 1000 seconds. You can always use a lower resistance value but then you have to make sure you resistor wattage is not exceeded. P = IV or Vsquared/R. So if you have a 1000 kV capacitor and a 1 kOhm resistor you would be dealing with 1000 W! if you used a 1 MOhm resistor you would be dealing with 1 W. High resistance value are safer in a sense but you have to make sure you wait long enough. Hope that helps
@@HTMWorkshop Thank you, but i'm still a little confused. What unit represent Time constant (second?), R (kOhm or Ohm), C (uF or F), V (kV or V), and what is I? Let say i need to discharge a 400V 60uF capacitor in 60 seconds, i'll need a 0.4W 1kOhm resistor? I can't seem to work out the formula, can you help me with that? Thank you very...very much.
@@mrdzin1209 Time constant is in seconds - you have to make sure R and C are in the base unit (ohms and farads). I is current. You will discharge that capacitor much faster than 60 seconds with that setup but you will need a 160 W resistor (I am doing those calculation pretty quick but I believe that is correct). You probably are not taking into account the unit prefixes for the first part. For the power calculation you need to make sure you square the voltage and then divide by resistance
@@HTMWorkshop Thank you, it's very helpful. And you're right about my setup, it would need a 160w resistor and discharge in 0.36 seconds (so a 16w 10kOhm resistor in 3.6s would be much more efficient). I believe you do that calculation in your head and that's freaking amazing.
Sounds like you got it, always a good idea to check with a voltmeter after discharging to verify. Or if that is not an option use a screwdriver to discharge any remaining charge (better to have a damaged board than a damaged hand)
Haha hey, you have the same oscilloscope and multimeter as me lol. Always nice to see another Tack Life user out there. In my opinion they make pretty great equipment for the low cost they charge.
Yes in general, if you had multiple sources for example you could use 200 V sources you could put them in series to create a 400 V source - but your still ultimately using a 400 V source
Hello, great video. A question: is it enough to have any resistor to discharge any capacitor ? I mean, can I have only one size so I can use it with a small capacitor or with a large one ?
resistance too high and it won't discharge. resistance too low and it will melt or catch fire. it matters, you can't just use any. it will depend on both the voltage and the capacitance of that specific capacitor.
Awsome video although I like to have the same setup you have transformer and rectifier can you posted the design setup so I can do the same on my little lab. appreciated... thank you;.
to be honest I am not sure - wish I could be more help. you should be able to use any DC supply and high voltage transformer for the type of walk through shown - but if you needed to worry about power/current of the device that may get tricky to make sure you down draw to much power.
One thing you forgot to discuss, is dielectric absorption. It can cause capacitors that have been discharged to regain some charge after some time, amd could lead to a nasty surprise.
Theoretically yes if pacing is not needed (there are some arrhythmia that require shock to be delivered at a specific time). That does not mean it's a good idea - since in practice you would want to size the capacitor correct, make sure there is appropriate contact with the skin (so as not to burn the body), make sure you did not discharge to much power into the power. It is possible but not advisable. Also there are different waveforms that are better than others for starting the heart - but a single capacitor can not control that. So in theory yes - in practice no.
@@davidvankeuren6575 My wife and I had been discussing repairing our microwave oven as a DIY project on an old GE Spacemaker 1400 microwave. After reading about multiple instances of fatal microwave repair projects; we've decided that it will be safer to take it to an appliance repair shop. I am sorry to hear about what happened to your friend.
This was some great presentation of information thank you. I am not strong in electronics but I am studying up to disassemble a digital camera that has a flash, and the manual states to discharge before taking of a certain part at these points. However it does not state which items I'd need. From my understanding are these ceramic resistors so big that I can order the same one I see you use or another video that I should be okay to use it for most "safe" capacitors, or do I have to do some math to match a capacitor every time? I guess my question is more of an is it "a rule of thumb" question, as I'd assume its always safe to calculate what you're working with.
Good question - I don't have a good rule of thumb for which resistor to select - if you select one that is to high it may take forever to discharge and if select one that is to low your going to pull too much wattage (and fry your resistor or worse). I recommend calculating the power and the time constant if your going to discharge things yourself for high large voltage large farad caps. But if the voltage is below 24 (or even 100 V) in most cases your not in trouble and if the capacitance is in nF or uF that is pretty low so it will discharge pretty fast. I don't work around a lot of equipment I am willing to do general rules (to expensive to replace) but if the equipment is not to expensive I would use a 1 Mohm high wattage (20 W resistor) or something like this amzn.to/3yIYoRx. Hold that on the leads to discharge for a little while, then check it with a multimeter to see how much voltage has dropped, if its going to slow get a lower resistance and try again. Hope that helps a bit.
what about 50v 6800uf capacitor? got 2 of those and 4 25v 1000uf capacitors in an amplifier board that i wanna take apart. it hasn't been plugged in for months
Well I would think the capacitors probably fairly safe (but that is a guess I don't know what your board looks like) - I would just check them with a voltmeter. If they read 0 volts then you know they are already discharged. If not, use a high ohm resistor to slowly discharge them to protect the electronics. My guess is they are already discharged.
Can’t you just wait a certain amount of time and they’ll discharge? I’m going to recap a Nikko amp and it will be unplugged for at least a week. Can the big caps hold a charge that long?
In most cases that can work but in some cases the cap may be very big and the discharge may take a while. In some systems there is not a bleed resistor to help discharge the cap when the device is off (depends on the device and application)
If you disconnect an amplifier (ie: 500w ClassD stereo and/or subwoofer amp with toroidal) approx. how long till all the capacitors discharge to a safe condition all on their own?
It depends on how big the capacitor and how big the bleed resistor is... best thing to do is measure it with your multimeter in voltage mode to see if there is any charge left
I brought 2 capacitor online, both are the same 820uF200V. It label with numbers on top and feel and look like plastic. Is it going to melt? Because capacitor can go to 105ºC. And I am new for repairing electronics.
Plastic is not necessarily a bad thing, most electronic plastics can take 100 degrees C. It will depend on the manufactures specs and their reputation, how long you run the caps, and of course statistics (since there are always things that can fall outside the norm). If I was betting on it I would say they are safe, but you may want to check the spec sheet for any info on temperature sensitivity.
@@HTMWorkshop Thank you, for advice, because I had no idea. Originally the television didn't bother turn on nor hearing power is on. With help of google and RUclips searching for board has power. I did spotted 2 or 3 capacitor, needs to be replace.
I have an old shortwave diathermy machine (Mettler 300) that seems to be malfunctioning, tubes seem to get hot (tubes have been changed as I first guess) but the coil doesn't seem to be hot. Under the lid are 2 separate capacitors (each set has 5 separate 28pf 5kv in joined parallel -- for 140pf 5kv each). I suspect these capacitors failed. To the look everything else seems okay and to the eye some capacitors appear to have cracks in them. These capacitors (10 in total) are ceramic disc capacitors. Warnings on the inside of the equipment to not work on it. No videos/aricles anywhere on how to discharge these. Machine has been unplugged for months.
Could be the issue, very high voltage. Yeah a lot of manufacturers say not to work on their equipment - this is more of a legal issue that a technical issue. The OEM is trying to protect themselves legally more than anything. I am sure they would tell you only a certified person should work on their equipment and tell you that it costs thousands of dollars to take the training. The capacitors are probably are not charged up, but better safe than sorry. I would use a high voltage discharge stick to see, ideally with an indicator LED. Then you can use your meter to confirm no voltage and try the repairs. But of course the OEM warranties and such will all be invalid but I am guessing that is already the case. I don't know who you work for but obviously they would need to be comfortable with the repairs and risks of repair.
Well if you calculate the power at 450V and 220 ohms I get 920 W - so your going to exceed your resistor power capacity - choose I higher ohm resistor to reduce the W
V = I * R --> I = V / R P = I * V --> P = V^2 / R P = 450^2 / 220 = 920 W R = V^2 / P R = 450^2/25 = 8100 ohm So, you need at least 8100 ohms to safely discharge that capacitor. Just get yourself a 10,000 ohm resistor and that should do it.
Not sure - depends on who made it and how well it holds up to the stress of the discharge. You can always charge it back up and see if it holds a charge. Very well could still be good - do you see any visible damage? What are you using it for?
You look like a master. Can you just point me in the right direction? I have a Mark Levinson no.27 amp. When I turn it on I heard a strong pop on the right speaker and then the unit went into protection mode. Even time I turn it on after that the power switch would pop back to off. Same result with all cables off with only power plugged in. The power light still lights, fuse is good. Can anyone give me some guidance? Thanks
Not sure on that one - sounds like some sort of current issue. Honestly, I would be looking in the user manual to see the reason for protection mode - start narrowing them down one by one to see if any of the suggested corrections work. My guess is you may have already tried that but can't say I'm familiar with that amp.
What about using gloves to prevent shocks/electrocution? Like those that linemen wear for their work. These gloves might be too cumbersome to wear all the time but I imagine they could be useful to have when in doubt
Yes you definitely could - but you can still damage the electronics if you are discharging the cap near the board. So that only works well if you either don't care about the device or if you have already removed the cap.
By "touching it" do you mean touching both terminals at the same time, or getting shocked by only touching 1 terminal. Can you be more specific? I have an Ampeg svt I am going to take to a tech but I need to educate myself and do it eventually.
You could potentially get shocked by only touching one terminal. It has to do with potential difference - so if you touched the terminal that is at a high voltage with respect to ground (aka the potential of where your touch feet or other path to low voltage if another part of your body is touching something). Current would travel from the touched terminal to the low voltage drain. This is one reason that people where high resistance rubber shoes or something of that nature to reduce the chance of large currents running through your body. It's also why line workers (or birds for that matter) can touch high voltage power lines and be safe (there is no easy, low resistance, path to ground). If you need to touch a lead on the capacitor the best thing would be to drain it first, then verify there is no potential difference with a voltmeter.
iit is not because the max voltage supported by the capacity is 400V that you will charge it at 400V, this is the max allowed DC + AC ripple voltage supported by the cap.
Well, I assume you mean in an off state (meaning not used to power anything), in that case it depends on the amount of leakage current. So if you had 1 Farad of capacitance fully charged you could figure out the time constant using t = Resistance * Capacitance. So you would need to know the effective resistance for the leakage circuit. Then multiply the time constant by 5 to get the effective discharge time...or you could just charge it up... then measure the voltage over time and see when it starts to drop (more of trial and error type method). Here is a general video on the time constant if your interested ruclips.net/video/JcrlL8YN6VQ/видео.html
@@HTMWorkshop it’s an Xbox brick power supply I had to ask first ! 2 in there are 200v 450f and 4x 16v capacitors as well ! Did not know if over time or if I needed a resistor to drain them but it did over time apparently
Possibly - it depends on what the capacitor is designed for. It is hard to say - but you can usually tell by charging the cap back up and seeing if it holds the charge. If it is leaking current then something is wrong...or if it doesn't charge at all well obviously its time to toss it. There is a decent chance its fine and will still work
Great video, would have liked to see how to test the charge. I know you can use a multimeter, but they are very sophisticated alien-like devices. I don't know what setting(s) are proper for what scenarios.
Thanks - by charge were you interested in measuring voltage or capacitance? You can check out this multimeter video on our channel if you want ruclips.net/video/BxVbLKd5Kk4/видео.html
@@HTMWorkshop I'm just concerned about residual electric during electronics repair thru simple replacing of parts. For example, people say computer power supply units can have a deadly charge in them for a long time. How can you really know without testing them? I assume that's the only other major thing to look out for, aside from making sure the device is unplugged of course. Thanks for the link.
@@lakecityransom I have worked on quite a few computers - I have not seen to many capacitors dangerous enough to pose an issue. I have often heard that if you disconnect the power then hold the hard reset for about 10 seconds you can discharge any remaining charge in the supply - but I would be surprised if that was even necessary. I would be more worried about damaging computer components through ESD than getting shocked by a computer that is unplugged - most everything in a computer runs on low voltage - except the power supply. I mean it's possible you have some sort of super cooled computer with crazy fans and motors that are not normally included but most parts are low voltage. If your just changing boards or ram you really don't have to worry about getting shocked (just unplug the power cord since the line voltage is the only real thing to worry about). Now I am assuming your not dealing with a CRT screen computer - if you have a computer that old then yes you do need to worry about a high voltage capacitor (but only for the CRT screen).
@@HTMWorkshop Oh for sure I've worked with computers a lot. I actually mean working within the PSU unit itself. There are cases of teenagers dying if you Google on that. The most common reason to open one up is the PSU fan's bearing goes bad and starts making a lot of rattle. Its simply a matter of replacing it with another standard 80mm or 120mm case fan. However, you do have to open it up and all the parts are in there tightly so it is concerning to attempt unhooking one and putting the other one in. I replaced a water intake control on a washing machine the other week and was questioning once again how safe I was being without testing components for residual electricity, but I did get the job done lol...
@@lakecityransom Yes it is possible - many psu utilize capactive reactance to step down mains - I believe those are suppose to be designed with a bleed capacitor - but I am not sure. You should be ok to replace the fan - just be careful around any caps that read over 20 V. I would imagine the fan should only have a couple connections or more likely a single molex connector. Which should be safe to unhook and change out. If you want to be extra safe you just make sure to take your meter and put it into voltage mode - then measure across the capacitor legs - and make sure the voltage is low. Always good to take of jewelry and use one hand as much as possible to reduce risks but I would imagine its fairly safe unless your really messing around near the caps (and even those should discharge pretty quick if the circuit is setup correctly).
Is there a reason they don't put some kind of international hazard warning, like a skull and crossbones, or at least a stop sign, on all high output capacitors?
Well its hard to draw a line in the sand and say this one is hazardous and this one is not - depends on a lot of factors. Its a good idea though and I do see some high voltage stuff marked (not quite like that but definitely a hazard warning)
I never discharged a capacitor by shorting it with a screwdriver. Instead, I used a 40W incandescent lamp with a bare wire. I connected this lamp to the capacitor terminal during which it will light up briefly and then fades
If by safe you mean for people, yes it is relatively safe for the the operator. However depending on the board electronics you want to be careful not to damage any part of the board. Make sure you understand the function of the capacitor before discharging to be safe for both the operator and the device.
The microwave capacitor shows 0.7 uF. I know the voltage is high (if charged high), but the capacity is low (?) even if the miniscule time period is enough to stop a heart. Please comment. Thx.
Well it will depend what your goals are, but in general if they are just to safely discharge the capacitor you can always use this calculator www.digikey.com/en/resources/conversion-calculators/conversion-calculator-time-constant Then get a time constant of around 1 second. At 5 seconds or 5 times the time constant you will be about 98% discharged. Obviously if you need to discharge the capacitor slower or faster you can. You would also want to make sure the power through the resistor does not exceed the resistor limits (measured in Watts).Remember - power = V^2/R. So if you wanted to reduce the power through the resistor choose a higher resistance (since voltage is fixed with your capacitor). Hope that helps.
Wait you discharge your capacitors by touching the leads with the screwdriver, I do it by touching the top of the body with a screwdriver, when and why would I have to discharge a capacitor again before testing and replacing? Or after
Not sure what you mean at the end there - while it is possible to discharge a cap with screwdriver - it is not the best/safest way when dealing with high voltage and sensitive electronics. I don't remember the video saying to discharge twice - but if you give me a timestamp I might be able to elaborate.
Hope the video was helpful! If you need some tools recommendations check below
Quality meter to test voltage of capacitors - amzn.to/3x7P5eL
High Voltage Discharge Stick amzn.to/3x4BuVt
Drivers to use around high voltage - amzn.to/3j8zweN
Question: Blower unit capacitor in my Bryant forced air heater might be bad. So… before I attempt to remove it, how long after cutting off all power to unit, will it take to discharge on its own? An hour? A day?
Thanks in advance for your response.
@@john-robert1961 Not sure, but if it was me I would turn it off. Then go measure it with my multimeter. Then I would wait a few minutes and check it with my multimeter again (voltage setting). See if it's discharging on its own and how fast.
@@HTMWorkshop thank you kindly for your rapid response. Naturally, I would turn off the main wall switch that connects to the unit, before even attempting to test anything. I will do the voltmeter test, followed by the capacitor test. I’m glad that I have encountered your video earlier this evening, it’s very informative.
@@john-robert1961 Back in the day, it's amazing how many people went POKING around (INSIDE) those old VACUUM TUBE TV's with a SCREWDRIVER!🤯😁😆😂🤣😂 BEFORE properly discharging the Capacitors! What a SURPRISE they received!😆😂🤣
My trick for those 200V or 400V capacitors is to use a lightbulb with wires soldered to it and just discharge it using the bulb, best to use an old fashion one with wire inside it, really useful when you are dealing with such voltage.
Good visual indicator - although I prefer to use a couple lightbulbs in series for something as high as 400 V.
For as long as I can remember, my dad keeps a lightbulb on some wires in his tools, which he uses to test circuit completion when doing house electrical work. Of course he first finds the live phase with a tester, and then checks with the lightbulb to be sure the ground is also connected.
Why not use a voltmeter you say? Well he says, "I don't have a third hand to hold it with".
@S Wong it can but only for low current situations! Most LED's can take around 20mA so you do not want to exceed the max current (or else your LED will turn into a fuse - which is not the end of the world since most LED's are cheap but it may fool you into thinking your capacitor is discharged when in reality you just fried the LED).
@@HTMWorkshop this was a very in-depth explanation. Thank you!
Just curious doesn't the filament have to heat up first before it offers resistance? Do use a 400 watt bulb?
I just discharged a 450v to the palm of my hand let's say I have 2 boils now and pain.... that's why I am checking this video out....
Electrical burns can definitely hurt. Hope your ok, glad your learning from your mistakes! “The only real mistake is the one from which we learn nothing.” HF
@@HTMWorkshop it still hurts after 1 day and I have a massive boil but I still need to see how to discharge these 450v I work with I repair consoles and they have 2 of these big capacitors I saw something on the internet to connect a light bulb to alligator clips and discharge it that way but I wasnt successfully in riggin something up so I just used the old screw driver but they discharge extremely dangerously in my opinion and I dont want to blow one up in the system.....
@@176cgna Yeah a screwdriver is just releasing the energy very quickly (and that means things can get hot), you need a good high Watt resistor (and decently high resistor, depends on how many Farads you are dealing with and how quick you want to discharge - has to due with time contact of an RC circuit). Most incandescent light bulbs are rated for 60W, and have a pretty low resistance of 120 ohms, so for a 450 V source you are roughly looking at around 3.75 Amps (most bulbs are rated around 0.5 amps). So not a great solution for high voltages. Some places sell high voltage discharge sticks for about twenty bucks if you want a profesional solution. But if you can find a high watt (2 W or greater with a resistance of around 100 kohms, that should work, just may take a while to discharge depending on your capacitors)
@@HTMWorkshop ah ok ima look for that tool I dont care about price and I work with these capacitors enought to warrent the purchase of a professional tool
@MyMate Leyto35 Thanks!
Great video! I wish they explained things this well when I was in school. They probably did I just didn't get it at the time. Age is not always a bad thing! Thanks for the info.
Great comment, so true.
they cover it indirectly if that is of any constellation. For my CompTIA A+ they said that if you get trained to work on televisions you will be taught how to properly discharge the capacitors, then in electrical they explained the relationship between resistors, capacitors, and time. Then throughout electrical they regularly explain that oftentimes steps often considered not recommended are the safest way to do tasks while implying that shorting a connection is sometimes the case.
Never once do they explicitly teach anything about properly discharging a capacitor but by the end you have tons of hints. So for this reason I am very happy to learn the specific recommended process for the first time and as such I would very much like to thank the video author.
I came to send this video to my neighbor. I once saw a dog lick a charged capacitor by mistake while a parent was getting tools to repair an opened microwave. The dog was flung off and hurt pretty bad. It stuck with me. I was walking by this morning when I saw a guy taking a microwave apart. I asked if he discharged the capacitor first. When he said the what now? I told his wife please get him away from it. He will get hurt! I then sent them your video. DAMN People! Come on!
I remember fixing tvs and vcrs It's good to have the knowledge
I'll never go anywhere near the insides of my guitar amp, and now I know why, instructive video, thanks
Apart from changing a tube, I'll leave it to someone competent. I'm too forgetful to mess with the innards of an amp and would die probably
Always cut the trailing ends of strings off when you change them was good advice I was given. 1: So you don't blind someone and 2) They can penetrate electrical equipment!
I really learned a lot from this video and I sincerely thank you.
I hope you make a video teaching how to safely discharge a higher voltage capacitor-not necessarily the 2100V type, but the 200V to 400V range might be helpful.
For reference regarding the 2K capacitors, it may add perspective for people to realize that the electric chairs used in the electrocution of condemned prisoners typically delivered around 2,000V. Granted, they were higher amperage (7 to 10A) and the charge was delivered for several seconds, but it gives us an idea of the seriousness of 2,000V.
Yeah 2000V is high - yes 200 and 400 V are often used to start motors and fans (things that need high torque). Good idea.
That’s is fuccking painful for 2000 V and 1-10 A. Holyshitttt.
Very good video and explanation, i once thought about touching one of capacitors even though it was only 25v and at that time i didnt know what those things were and well i have to say thank god i didnt touch them and thank god it wasnt a high voltage capacitor (didnt know what was going through my mind at that time xd)
Thanks, very well explained. I’m gonna be much more cautious taking electrical/electronic stuff apart going forward.
Excellent explanation. Likely saved me from getting hurt today.
Good to hear!
I didn't learn what I wanted from this video but it was strangely very entertaining (I thought this video could teach me the recommended specs for a capacitor dischargwr)
I've been dealing with caps for decades, so I didn't learn anything new from the video, but I was highly impressed with your teaching style, calm and steady and looked like you prepared well. It is obviously aimed towards beginners, and you reduced the topic to its essential elements, and explained them simply. I was hoping to see what you had to say about BIG caps, I worked at a 500 Kilowatt shortwave station. Can't say "my loss" as I enjoyed watching your video. 73deK1WXY
Are there any other components you should be carefull with?
Anything involving high voltage.
Current transformers...If the secondary has no load, the secondary voltage can soar to very high voltages. Won''t explain why here, google it.
Large batteries...Watch your jewelry. If metal watch band or bracelet shorts out a large amperage battery, you will not be electrocuted, but may get an impression of the jewelry BURNED INTO YOUR WRIST. Can and has happened to people reaching up under the dashboard fiddling with stuff up under there. A ring contacting the battery terminal on the rear of the starter switch melted a friend's wedding ring into his finger, ouch.
Any one else got any suggestions?
@@robertstessel8780 Thanks for the great answer! Will keep this in mind.
Thank for the knowledge sir I really appreciate it.
One of my relatives son telling about his experience about electronics and then he told us about capacitor thing and tell us how dangerous it can be that's why I am here to gain knowledge.
You are a great teacher! The video was great to watch. Thank you.
Thanks for this video demotration, really a life saver for people like me who has zero knowledge in electronics.
Glad it helped!
fantastic video sir. I wish I had an electronics teacher like this in high school.
You made this so easy to understand. Great channel
thanks!
I use solder wick to discharge or verify discharge if not in circuit. I have a 8 Ohm 10 W resistor (used for ESU testing) I use for board discharges (with jumper wires of course)
🤔Interesting. I have not used solder wick for that application, but I see n no reason not to as long as you are ok with a quick discharge. Nice tip if your doing board work and some handy. The 8 ohm resistor would definitely be a good discharge resistor. Out of curiosity what test are you doing on the ESU with the resistor?
@@HTMWorkshop Covidien FT10, Force triad etc need to detect a patient load in order to energize
Great video, thank you for taking the time to make it!
Excellent video! Very underrated! well explained! Thank you very much sir 😄
Thank you!
Also, as a note, that resistor is 5 watts which means it can take higher power. (Little resistors are 1/4 W or even 1/8 W. Not sure what surface mounted ones are rated at.)
I have three microwave capacitors rated at 2100V sitting around my house not yet discharged! Just realized I'm lucky to be alive, and that is why I am watching this video.
RUclips can save you. Thank god I watched that video about what grenades do.
Usually, they have resistors built in to discharge themselves. But, it's always a bad idea to rely on one point of failure with big caps. Capacitors can also spontaneously develop a charge to do dielectric re-absorption. I personally like to keep them permanently shorted out with alligator clips like that, just in case!
@@HTMWorkshop - Excellent explenations for capacitors. I didn't know that they could charge on their own. Thanks
@@HTMWorkshop l
How did we get here
Just curious does that open part at the top also conduct electricity?
I am replacing the two capacitors on my subwoofer amp. Both are 80V 6800uf. Can I use the screwdriver method to discharge them?
Yeah you should be fine, may spark a bit but your safe enough
Great video, professor 👍
Im wonder if the high V caps can discharge if even just placed close to oneself or if contact necessary
Contact is not technically necessary but resistance is usually pretty high without contact
So I have 4 Caps that are in the power supply circuit of a stereo processor. It's 19.5V AC feeding 35V 470uf Caps. I need to replace them as a few have begun to leak. Do I need to worry about discharging them before un-soldering them from the circuit?
20 V is pretty safe, 35 V is still pretty safe but on the edge of possible issues. I personally would not worry but if you want to be extra safe I would just use a screwdriver to discharge them (or some other piece of metal)
Thanks for this this informative video! I need to remove a very old high power xenon lamp igniter and want to do so safely and not get knocked on my butt!
Hope it goes well!
why not use resistor to discharge capacitor that has high voltage if you are holding the ceramic part?
what would you suggest to use to discharge over 1,000 volt capacitor when usually equipment insulated for just 1,000?
thanks
You definitely can use a resistor but you need to make sure you get one with an appropriate wattage rating. You can reduce the power with a higher ohm resistor but then the higher the resistance the slower the discharge. I would use one of those high voltage discharge sticks I have in the description otherwise you can size out the resistor you need if you have a bunch of high wattage one - but for most people they don't want to bother with doing the calculation
Thanks! What res is recommended and up to what voltage cap? And is it alright to touch the leads of that res when doing that? Also is a discharge pen recommended for higher voltage?
That depends a lot on the situation - for instance do you just want to discharge the capacitor or do you care about keeping the circuit integrity and capacitor working afterwards. A very consdervative basline is around 24 V - I don't mind touching 24 V shorted but if you discharge a 24V cap fast it may damage the circuit around it (depends on the situation). In practically I wouldn't mind discharging a 500 V capacitor if it had a small capacitance and a insulated handle - but that is getting more risky and could easily damage the circuit. It really has to do with your risk tolerance and what your comfortable with but always best o err on the side of safety if you don't have a good grasp on the circuit and your own risk.
Best video on the subject, very informative, thanks.
Thank you!
Useful video 👍. Can i use a 20M ohm potentiometer to discharge it?
Thanks - depends on what type of power the potentiometer can take. The resistance is good - but if you run to much current (at a high voltage.. remember Power = current x voltage) then you may burn up the potentiometer. I would not recommend it for discharging very very high voltage things - but my guess is for most applications it would be just fine since it is just a high resistance - and therefore low current.
Excellent! Many thanks for explaining this so clearly.
Do you have to touch both leads / connections of the capacitor? And the shock happening in what is between the leads? Or is it a matter of charge being able to go to ground? In which case, is only one of the leads actually dangerous (the one with electrons at it's disposal to send out)?
Usually, yes between leads. Touch current is going to be negligent unless one of the leads of the capacitor is already grounded (in which case if you touch the other lead it can still discharge). In other words caps are not by nature grounded but if you connect one lead to ground then the other lead is going to be dangerous (if its at high voltages)
When you discharged the capacitor with the resistor, did you touch both metal wires of the resistor
with both metal parts of the capacitor?
correct (botht he anode and the cathode of the cap)
@@HTMWorkshop Thank you! If the wires of 1 resistor are not long enough, could I use 1 wire from 2 different resistors to discharge the capacitor still?
@@grooty6434 Im not exactly sure what you mean - you can use two resistors in series - yes. There must be a path between the leads of the capacitor - what you put in between determines how fast the discharge (based off resistance mainly) - see more info on time constant of caps for how long it will take
Do the microwave capacitors tell you how long it takes to bleed out that voltage once they are unplugged? I'm guessing a few seconds. Still makes me nervous.
I don’t think the manual will tell you...but your probably right. Assuming all is working correctly. Best to unplug, check with a voltmeter then do a quick discharge to be extra safe.
@@HTMWorkshop microwaves capacitors are around 2kv - 4kv , what size/type resistor would be needed to safety discharge the capacitor?
@@raybradshaw8444 It would depend on what kind of wattage the resistors could take. Maybe a 1 MOhm resistor ... but it could take some time to discharge depending on how many farads. Often you see 100 kOhms used in high voltage discharge sticks.
@@HTMWorkshop as a basic sum it took 15sec with a 50kohm (3 R in a sting) tool on 300v, and 30sec with a 100kohm (6 resistors in a sting) on 300v, so dum math says 300secounds with the 100kohm so 5mins for 3000v.
i just dont know if my little 100kOhm Tool will handle 3kv and not melt like a icepop, lol
@@raybradshaw8444 It just depends on what the resistor is rated for power wise - is it a high Watt resistor? The higher the resistors the slower the current will move so you can use lower watt resistors (its a tradeoff between power the resistor can handle and time it takes t discharge). You have to check both.
I have read through some of the comments. I have worked around 400 volt lines and higher as a research scientist.
Around 400 volts, there is an invisible charge cloud or corona about these lines and devices connected to them. If one is grounded, burns, neurological and brain damage and death can result without direct contact. An kindly older electrician told me this when I was 24 or 25. He saved me injury and death many times over.
Good point - yeah I use to work with 1-10kV and your right (everything even air becomes a conductor at some point and ions can form). I use to do some electrospinning back in the day, and it takes advantage of that very effect.
Thanks for the video. I’m looking for an example that explains what size resistor is needed, or should be used with, the capacity trying to be discharged?
Hmm - I don't exactly have a video on that. I do have a blog that may be helpful here htm-workshop.com/how-to-discharge-capacitors-safely/. Also I know in a couple of the comments for this video I explained some specific resistor choices for caps. The key is understanding the power the resistor can take and how fast you want to discharge the cap. P = IV or V2/R , so don't exceed the power rating of your resistor or you will fry it - also the time it takes is based of the time constact for a capacitive resistor circuit ruclips.net/video/JcrlL8YN6VQ/видео.html. A 10W 1MOhm resistor may be a good place to start but it is very conservative (for most circuits)
Wanted to ask a question in regards to discharging using a ceramic resistor like you did in this video, I noticed when you were discharging you still had part of your finger on the metal bit of the resistor, Is that safe to do so?, Also does it matter what polarity the resistor is to the capacitor?, I'm assuming it doesn't have polarity and doesn't matter which way you discharge it, whether its face down or face up. Lastly do both the legs of the resistor have to make contact with the legs of the capacitor at the same time for discharging?
TIA
Resistors do not have polarity and yes both legs of the resistor must touch both legs of the capacitor to discharge. As far as if its safe to have your finger touch the metal part - the answer is maybe but best practice is NOT to touch it. Certain voltages are perfectly safe but if you are not that familiar with safe voltage I would just stay on the safe side.
PS: Up to what voltage is the screwdriver method safe?
Thanks for sharing im almost have a heart attack when i saw the spark when you discharge the capacitor 🤣🤣
How do you determine which resistor to use to discharge which capacitor?
Good question, depends on how how fast you need to discharge the capacitor. Time constant is a key factor to determine how long it will take, time constant = RC. So if you had a 1 uF capacitor and a 1 MOhm resistor it would take 1000 seconds. You can always use a lower resistance value but then you have to make sure you resistor wattage is not exceeded. P = IV or Vsquared/R. So if you have a 1000 kV capacitor and a 1 kOhm resistor you would be dealing with 1000 W! if you used a 1 MOhm resistor you would be dealing with 1 W. High resistance value are safer in a sense but you have to make sure you wait long enough. Hope that helps
@@HTMWorkshop Thank you, but i'm still a little confused. What unit represent Time constant (second?), R (kOhm or Ohm), C (uF or F), V (kV or V), and what is I?
Let say i need to discharge a 400V 60uF capacitor in 60 seconds, i'll need a 0.4W 1kOhm resistor?
I can't seem to work out the formula, can you help me with that? Thank you very...very much.
@@mrdzin1209 Time constant is in seconds - you have to make sure R and C are in the base unit (ohms and farads). I is current. You will discharge that capacitor much faster than 60 seconds with that setup but you will need a 160 W resistor (I am doing those calculation pretty quick but I believe that is correct). You probably are not taking into account the unit prefixes for the first part. For the power calculation you need to make sure you square the voltage and then divide by resistance
@@HTMWorkshop Thank you, it's very helpful. And you're right about my setup, it would need a 160w resistor and discharge in 0.36 seconds (so a 16w 10kOhm resistor in 3.6s would be much more efficient). I believe you do that calculation in your head and that's freaking amazing.
Sounds like you got it, always a good idea to check with a voltmeter after discharging to verify. Or if that is not an option use a screwdriver to discharge any remaining charge (better to have a damaged board than a damaged hand)
Haha hey, you have the same oscilloscope and multimeter as me lol. Always nice to see another Tack Life user out there. In my opinion they make pretty great equipment for the low cost they charge.
Does a 400v capacitor need to have 400 volt source to charge it fully?
Yes in general, if you had multiple sources for example you could use 200 V sources you could put them in series to create a 400 V source - but your still ultimately using a 400 V source
Really educational video, thanks!
Outstanding video, thank you very much.
Excellent video, thank you for the knowledge!
Thank you!
Thanks. Great explanations!!
Hello, great video. A question: is it enough to have any resistor to discharge any capacitor ? I mean, can I have only one size so I can use it with a small capacitor or with a large one ?
resistance too high and it won't discharge. resistance too low and it will melt or catch fire. it matters, you can't just use any. it will depend on both the voltage and the capacitance of that specific capacitor.
Awsome video although I like to have the same setup you have transformer and rectifier can you posted the design setup so I can do the same on my little lab. appreciated... thank you;.
to be honest I am not sure - wish I could be more help. you should be able to use any DC supply and high voltage transformer for the type of walk through shown - but if you needed to worry about power/current of the device that may get tricky to make sure you down draw to much power.
Thats why i click on this video to safely discharge hig voltages ones!
One thing you forgot to discuss, is dielectric absorption. It can cause capacitors that have been discharged to regain some charge after some time, amd could lead to a nasty surprise.
after getting taserd by that 400v in my laptop ac adapter while trying to repair it via replacement.. I'm here to learn to discharge that thing
Yikes! hope the video helped! Stay safe.
nice educational video thanks . the microwave capacitor: could that start someone's heart if there wasn't a set of paddles near by?
Theoretically yes if pacing is not needed (there are some arrhythmia that require shock to be delivered at a specific time). That does not mean it's a good idea - since in practice you would want to size the capacitor correct, make sure there is appropriate contact with the skin (so as not to burn the body), make sure you did not discharge to much power into the power. It is possible but not advisable. Also there are different waveforms that are better than others for starting the heart - but a single capacitor can not control that. So in theory yes - in practice no.
Nice so not a great idea to do this but good information for the zombie apocalypse lmao ....
@@MF-sy7zq That is probably the perfect way to say it... haha
my friend was killed by a microwave capacitor
@@davidvankeuren6575 My wife and I had been discussing repairing our microwave oven as a DIY project on an old GE Spacemaker 1400 microwave. After reading about multiple instances of fatal microwave repair projects; we've decided that it will be safer to take it to an appliance repair shop.
I am sorry to hear about what happened to your friend.
This was some great presentation of information thank you. I am not strong in electronics but I am studying up to disassemble a digital camera that has a flash, and the manual states to discharge before taking of a certain part at these points. However it does not state which items I'd need. From my understanding are these ceramic resistors so big that I can order the same one I see you use or another video that I should be okay to use it for most "safe" capacitors, or do I have to do some math to match a capacitor every time?
I guess my question is more of an is it "a rule of thumb" question, as I'd assume its always safe to calculate what you're working with.
Good question - I don't have a good rule of thumb for which resistor to select - if you select one that is to high it may take forever to discharge and if select one that is to low your going to pull too much wattage (and fry your resistor or worse). I recommend calculating the power and the time constant if your going to discharge things yourself for high large voltage large farad caps. But if the voltage is below 24 (or even 100 V) in most cases your not in trouble and if the capacitance is in nF or uF that is pretty low so it will discharge pretty fast. I don't work around a lot of equipment I am willing to do general rules (to expensive to replace) but if the equipment is not to expensive I would use a 1 Mohm high wattage (20 W resistor) or something like this amzn.to/3yIYoRx. Hold that on the leads to discharge for a little while, then check it with a multimeter to see how much voltage has dropped, if its going to slow get a lower resistance and try again. Hope that helps a bit.
what about 50v 6800uf capacitor? got 2 of those and 4 25v 1000uf capacitors in an amplifier board that i wanna take apart. it hasn't been plugged in for months
Well I would think the capacitors probably fairly safe (but that is a guess I don't know what your board looks like) - I would just check them with a voltmeter. If they read 0 volts then you know they are already discharged. If not, use a high ohm resistor to slowly discharge them to protect the electronics. My guess is they are already discharged.
super useful video. Awesome addition while studying theory
Thanks!
Very informative and well done. Ur a nice talker, gj good video :)
Can’t you just wait a certain amount of time and they’ll discharge? I’m going to recap a Nikko amp and it will be unplugged for at least a week. Can the big caps hold a charge that long?
In most cases that can work but in some cases the cap may be very big and the discharge may take a while. In some systems there is not a bleed resistor to help discharge the cap when the device is off (depends on the device and application)
Thanks for this video, very helpful
very informative, thank you
If you disconnect an amplifier (ie: 500w ClassD stereo and/or subwoofer amp with toroidal) approx. how long till all the capacitors discharge to a safe condition all on their own?
It depends on how big the capacitor and how big the bleed resistor is... best thing to do is measure it with your multimeter in voltage mode to see if there is any charge left
Please make video on how to safely discharge the high voltage caps thanks
I was thinking that, useful vid but doesn't quite deliver as promised in the title!
Excellent tutorial, thank you.
Glad it was helpful!
Very good video, thanks for taking the time & sacrificing those poor caps on the altar of education & safety!
I brought 2 capacitor online, both are the same 820uF200V. It label with numbers on top and feel and look like plastic. Is it going to melt?
Because capacitor can go to 105ºC. And I am new for repairing electronics.
Plastic is not necessarily a bad thing, most electronic plastics can take 100 degrees C. It will depend on the manufactures specs and their reputation, how long you run the caps, and of course statistics (since there are always things that can fall outside the norm). If I was betting on it I would say they are safe, but you may want to check the spec sheet for any info on temperature sensitivity.
@@HTMWorkshop Thank you, for advice, because I had no idea. Originally the television didn't bother turn on nor hearing power is on. With help of google and RUclips searching for board has power. I did spotted 2 or 3 capacitor, needs to be replace.
I have an old shortwave diathermy machine (Mettler 300) that seems to be malfunctioning, tubes seem to get hot (tubes have been changed as I first guess) but the coil doesn't seem to be hot. Under the lid are 2 separate capacitors (each set has 5 separate 28pf 5kv in joined parallel -- for 140pf 5kv each). I suspect these capacitors failed. To the look everything else seems okay and to the eye some capacitors appear to have cracks in them. These capacitors (10 in total) are ceramic disc capacitors. Warnings on the inside of the equipment to not work on it. No videos/aricles anywhere on how to discharge these. Machine has been unplugged for months.
Could be the issue, very high voltage. Yeah a lot of manufacturers say not to work on their equipment - this is more of a legal issue that a technical issue. The OEM is trying to protect themselves legally more than anything. I am sure they would tell you only a certified person should work on their equipment and tell you that it costs thousands of dollars to take the training. The capacitors are probably are not charged up, but better safe than sorry. I would use a high voltage discharge stick to see, ideally with an indicator LED. Then you can use your meter to confirm no voltage and try the repairs. But of course the OEM warranties and such will all be invalid but I am guessing that is already the case. I don't know who you work for but obviously they would need to be comfortable with the repairs and risks of repair.
I have a physically large resistor. It is 220 ohms and 25 watts. What would the pros and cons of using this on a 450 volt capacitor be?
Well if you calculate the power at 450V and 220 ohms I get 920 W - so your going to exceed your resistor power capacity - choose I higher ohm resistor to reduce the W
V = I * R --> I = V / R
P = I * V --> P = V^2 / R
P = 450^2 / 220 = 920 W
R = V^2 / P
R = 450^2/25 = 8100 ohm
So, you need at least 8100 ohms to safely discharge that capacitor. Just get yourself a 10,000 ohm resistor and that should do it.
Great video
Thanks for the education sir. I appreciate the video. I think I'll leave capacitors alone.
Ha - well maybe just stick to low voltage caps - they can be a lot of fun!
Very helpful ❤️
Sir , i have accidentally shorted a 70 mf , 400 V capacitor with a screw driver. my question is will it fully damage my capacitor?
Not sure - depends on who made it and how well it holds up to the stress of the discharge. You can always charge it back up and see if it holds a charge. Very well could still be good - do you see any visible damage? What are you using it for?
Thank you!
You look like a master. Can you just point me in the right direction? I have a Mark Levinson no.27 amp. When I turn it on I heard a strong pop on the right speaker and then the unit went into protection mode. Even time I turn it on after that the power switch would pop back to off. Same result with all cables off with only power plugged in. The power light still lights, fuse is good. Can anyone give me some guidance? Thanks
Not sure on that one - sounds like some sort of current issue. Honestly, I would be looking in the user manual to see the reason for protection mode - start narrowing them down one by one to see if any of the suggested corrections work. My guess is you may have already tried that but can't say I'm familiar with that amp.
What about using gloves to prevent shocks/electrocution? Like those that linemen wear for their work.
These gloves might be too cumbersome to wear all the time but I imagine they could be useful to have when in doubt
Yes you definitely could - but you can still damage the electronics if you are discharging the cap near the board. So that only works well if you either don't care about the device or if you have already removed the cap.
By "touching it" do you mean touching both terminals at the same time, or getting shocked by only touching 1 terminal. Can you be more specific? I have an Ampeg svt I am going to take to a tech but I need to educate myself and do it eventually.
You could potentially get shocked by only touching one terminal. It has to do with potential difference - so if you touched the terminal that is at a high voltage with respect to ground (aka the potential of where your touch feet or other path to low voltage if another part of your body is touching something). Current would travel from the touched terminal to the low voltage drain. This is one reason that people where high resistance rubber shoes or something of that nature to reduce the chance of large currents running through your body. It's also why line workers (or birds for that matter) can touch high voltage power lines and be safe (there is no easy, low resistance, path to ground). If you need to touch a lead on the capacitor the best thing would be to drain it first, then verify there is no potential difference with a voltmeter.
iit is not because the max voltage supported by the capacity is 400V that you will charge it at 400V, this is the max allowed DC + AC ripple voltage supported by the cap.
You are correct that the listed voltage is the max recommended voltage (any higher risks dialectic breakdown breakdown and could damage the cap)
Coldn't actually see the resistor discharge technique but I got the gist, thanks!
Great job but my question is that how can I change the capacitor after discharge please 🙏 sir
This helped me so much thanks my guy
Your welcome!
How long can they hold charge for ?
Well, I assume you mean in an off state (meaning not used to power anything), in that case it depends on the amount of leakage current. So if you had 1 Farad of capacitance fully charged you could figure out the time constant using t = Resistance * Capacitance. So you would need to know the effective resistance for the leakage circuit. Then multiply the time constant by 5 to get the effective discharge time...or you could just charge it up... then measure the voltage over time and see when it starts to drop (more of trial and error type method). Here is a general video on the time constant if your interested ruclips.net/video/JcrlL8YN6VQ/видео.html
@@HTMWorkshop oh man appreciate it
@@HTMWorkshop just out a volt meter to it nada
@@HTMWorkshop it’s an Xbox brick power supply I had to ask first ! 2 in there are 200v 450f and 4x 16v capacitors as well ! Did not know if over time or if I needed a resistor to drain them but it did over time apparently
I have just now discharged 100uF capacitor charged to 230 V using a flat file. Will it damage my capacitor? The rating of capacitor was 400V
Possibly - it depends on what the capacitor is designed for. It is hard to say - but you can usually tell by charging the cap back up and seeing if it holds the charge. If it is leaking current then something is wrong...or if it doesn't charge at all well obviously its time to toss it. There is a decent chance its fine and will still work
@@HTMWorkshop yes it's holding 230 V after the accident
@@abhinabachoudhury5843 Great!
Thanks ❤️❤️
Is it good or ok to replace 2200uf 35v with 2200uf 16v?
well I would say in general no - but its going to depend a lot on what the 35v capacitor is used for.
@@HTMWorkshop power supply I will go for 2200uf 50v then. Don't have 35v.
@@NengVang2007 I think that has a better chance of working - goodluck!
Thank you for your content. This video was very helpful
👍
Thank you for your video man appreciate it
Thanks!
Nice video man!
Great video, would have liked to see how to test the charge. I know you can use a multimeter, but they are very sophisticated alien-like devices. I don't know what setting(s) are proper for what scenarios.
Thanks - by charge were you interested in measuring voltage or capacitance? You can check out this multimeter video on our channel if you want ruclips.net/video/BxVbLKd5Kk4/видео.html
@@HTMWorkshop I'm just concerned about residual electric during electronics repair thru simple replacing of parts. For example, people say computer power supply units can have a deadly charge in them for a long time. How can you really know without testing them? I assume that's the only other major thing to look out for, aside from making sure the device is unplugged of course. Thanks for the link.
@@lakecityransom I have worked on quite a few computers - I have not seen to many capacitors dangerous enough to pose an issue. I have often heard that if you disconnect the power then hold the hard reset for about 10 seconds you can discharge any remaining charge in the supply - but I would be surprised if that was even necessary. I would be more worried about damaging computer components through ESD than getting shocked by a computer that is unplugged - most everything in a computer runs on low voltage - except the power supply. I mean it's possible you have some sort of super cooled computer with crazy fans and motors that are not normally included but most parts are low voltage. If your just changing boards or ram you really don't have to worry about getting shocked (just unplug the power cord since the line voltage is the only real thing to worry about). Now I am assuming your not dealing with a CRT screen computer - if you have a computer that old then yes you do need to worry about a high voltage capacitor (but only for the CRT screen).
@@HTMWorkshop Oh for sure I've worked with computers a lot. I actually mean working within the PSU unit itself. There are cases of teenagers dying if you Google on that. The most common reason to open one up is the PSU fan's bearing goes bad and starts making a lot of rattle. Its simply a matter of replacing it with another standard 80mm or 120mm case fan. However, you do have to open it up and all the parts are in there tightly so it is concerning to attempt unhooking one and putting the other one in.
I replaced a water intake control on a washing machine the other week and was questioning once again how safe I was being without testing components for residual electricity, but I did get the job done lol...
@@lakecityransom
Yes it is possible - many psu utilize capactive reactance to step down mains - I believe those are suppose to be designed with a bleed capacitor - but I am not sure. You should be ok to replace the fan - just be careful around any caps that read over 20 V. I would imagine the fan should only have a couple connections or more likely a single molex connector. Which should be safe to unhook and change out. If you want to be extra safe you just make sure to take your meter and put it into voltage mode - then measure across the capacitor legs - and make sure the voltage is low. Always good to take of jewelry and use one hand as much as possible to reduce risks but I would imagine its fairly safe unless your really messing around near the caps (and even those should discharge pretty quick if the circuit is setup correctly).
Is there a reason they don't put some kind of international hazard warning, like a skull and crossbones, or at least a stop sign, on all high output capacitors?
Well its hard to draw a line in the sand and say this one is hazardous and this one is not - depends on a lot of factors. Its a good idea though and I do see some high voltage stuff marked (not quite like that but definitely a hazard warning)
I never discharged a capacitor by shorting it with a screwdriver. Instead, I used a 40W incandescent lamp with a bare wire. I connected this lamp to the capacitor terminal during which it will light up briefly and then fades
This what i'm thinking. Thank you.
Can you safely discharge a capacitor using this method while it's still connected to a board?
If by safe you mean for people, yes it is relatively safe for the the operator. However depending on the board electronics you want to be careful not to damage any part of the board. Make sure you understand the function of the capacitor before discharging to be safe for both the operator and the device.
The microwave capacitor shows 0.7 uF. I know the voltage is high (if charged high), but the capacity is low (?) even if the miniscule time period is enough to stop a heart. Please comment. Thx.
Yup, helpful. Thanks
Glad it was helpful!
Dumb question, is there a way to calculate which resistor to use with which capacitor?
Well it will depend what your goals are, but in general if they are just to safely discharge the capacitor you can always use this calculator www.digikey.com/en/resources/conversion-calculators/conversion-calculator-time-constant
Then get a time constant of around 1 second. At 5 seconds or 5 times the time constant you will be about 98% discharged. Obviously if you need to discharge the capacitor slower or faster you can. You would also want to make sure the power through the resistor does not exceed the resistor limits (measured in Watts).Remember - power = V^2/R. So if you wanted to reduce the power through the resistor choose a higher resistance (since voltage is fixed with your capacitor). Hope that helps.
@@HTMWorkshop Awesome, thank you!
Wait you discharge your capacitors by touching the leads with the screwdriver, I do it by touching the top of the body with a screwdriver, when and why would I have to discharge a capacitor again before testing and replacing? Or after
Not sure what you mean at the end there - while it is possible to discharge a cap with screwdriver - it is not the best/safest way when dealing with high voltage and sensitive electronics. I don't remember the video saying to discharge twice - but if you give me a timestamp I might be able to elaborate.
Excellent. Thanks.
Glad you liked it!
Nice video
Nice vedio..
5:26 I specifically watched this video to try it at home lmao
I am sure you are not alone 😅