Once you play with the power off to discharge the caps, UNPLUG THE AMP FROM THE WALL before going inside the chassis, Should have put that in the video.
Having worked construction my whole life, and playing guitar, I learned that the neutral side of an outlet will shock you too, not as bad but not a good thing. Amps plugged in still get residual power from the neutral. Kinda like a back flow in reverse from the outlet
you are obviously a great tech so my endorsement means little there. What I can say however is over the last few weeks the quality of your youtube videos have gone up a lot. These last few have seemed to be more educational and the production has even increased- I realize being a tech first and a youtuber second- this may not be your overarching concern but it is appreciated for us out there who are learning some tips.
I've heard of this but never had to do it. As I never took my Deluxe Reverb RI apart when I had it. Your channel is probably one of the best amp channels on youtube. There will always be second guessers, it happens in any trade.
It is always reassuring and motivating to watch videos from like minded people with similar tastes, who also have an "old soul" to their character that help others understand often misunderstood concepts like the difference in an amps shortcomings, and what makes an amp "crap". you seem to maintain this mindset about a lot including yourself and other people and have a generally uncommon ability to see things for what they are, and for what they aren't. With that ability you don't seem to judge anything or anyone for more than they should reasonably be held responsible for and I respect the hell out of that. I love how your experiences in the shop with modern reissue amplifiers out of the Fender camp does not sway your love of that signature Fender sound has given you. To many people that would defy logic, but that just means that on a basic level they lack the experience and appreciation of something that impacts our lives in a unique and drastic way, which I think too many people nowadays have likely never experienced. I digress. There are quite a few aspects of your presentation and effort to educate that keep me coming back. You've been inspiring me to cautiously overcome my apprehensions about learning and understanding the complexity and dangers of amp circuits. I want to be able to keep the small collection I have functioning as they're designed, being respectful of the inherent dangers, so they can do their job of keeping a smile on my face for as long as I can play, hopefully passing on some of that joy to my daughter as she grows up as well. Cheers!
I really enjoy your videos. As a long time amp tinkerer it's helped me better understand what I should and should not do myself. Glad I didn't have to learn that stuff the hard way.
Just one time, I decided to use the screwdriver to discharge the caps - I will never forget the SNAP and the pit it left on the screwdriver!!!! Serious stuff! Thanks for the video!
I was helping a friend wire a car audio power amp (500w rms) up once and he accidentally shorted the output terminals I was amazed how big of a arc resulted. And this amp had been sitting for years. Ever since I’ve had a healthy respect for large caps in general.
I Wanted to check if my 66 bandmaster had original filter caps. The amp still held on to 15 volts after this method. I continued by draining it slowly with the meter. The filter caps were original. Thanks for the video!
This is the method I used when I went into my '67 Deluxe Reverb to replace those 55 year old filter caps. When I measured the voltage it was less than 1 volt anywhere in the amp. So I can confirm that this works. I haven't tried it with my Marshall JMP yet, but I will soon. I still want to make a discharge tool with alligator clips and a big 200ohm 10-watt resistor... I have everything to make it, I just haven't had time to do it yet.
I had forgotten about this-it doesn't pull it all out, but it makes it generally safe to do things like change jacks, replace the power cable, etc. Also do this before you change or remove a tube. I haven't worked on tube amps since the early 80's, and have forgotten all this stuff.
Thank you for your wonderful videos. I've got a blues deluxe reissue (unfortunately, now that I've discovered your channel) that rarely gets used because it's just too dang loud if you want that edge of breakup sound, and perhaps it needs a tightening of bolts and screws. Just out of curiosity, what voltage would there be if you hadn't discharged the capacitors?
Some circuits I use to work on (not guitar amps) used to have bleed off resistors to discharge caps, or you had to take a probe and discharge each cap to ground.
Older Fender amps with filter caps wired in series for the first node usually had balancing resistors across the caps and these also functioned as bleeder resistors, though the ohms value was high enough that the caps didn't drain all that quickly.
I've been doing THAT for years !! Usually do it on the bench with a signal generator and raise the signal generator as I unplug the amp . I discovered this when I noticed how long after you unplugged a Dynaco pre amp that it would keep playing ......if you did it THAT way , by time you got the chassis open the quad cap was just about zero , doesn't hurt to check with an alligator clip and a resistor either though . Nice vid and GOOD point !!
Yea I've always done the resistor bleed down thing too. Some amps have them built in if I remember correctly. But always verify, especially with tube amps. It's good to see another way though 🎸
@@mikewithers299 You gotta' be careful with it , more common with TVs and Oscilloscopes but every once in a while it CAN creep back up again too ! I always check with a 10 ohm resistor and an alligator clip to be sure .
@frankporfidio9813 yes I had it happen on a couple amps that I was changing out filter caps on. I drained them and removed the resistor, got side tracked, came back to remove them and volts creeped back up again. Glad I checked again before unsoldering it!
I have a quick question! Would it be possible to custom build a point-to-point clone of a Mesa Dual Rectifier (2 channel)? From what I understand the preamp is similar to an SLO but the power amp is different. I wouldn't need the tube rectification and could forgo the "spongy" feature. I'm asking because I know how challenging mesa products are to maintain. Thanks, I love the channel & keep up the good work.
What do you use as a minimum resistor to discharge caps when they won’t bleed down? My Fluke has a Low-Z input of 10k. I’ve bled down little things (on container ships) with it, and actually tripped an alarm by pulling down a signal voltage. Would it work for discharging a JCM 800 2204? I could solder something together with something higher, I even have some 1000v junk leads that I could splice something into. But if my Low-Z will handle it, it sure would be nice.
Thank you, great video. So if you have a bad power switch and unable to turn on the amp, then what do you do? You have to open the chassis to swap in a new power switch.
To discharge the filter caps you turn off the amplifier while strumming your guitar until it's dead sound but that doesn't mean their is still 350vdc charged voltage still holding storage on the filter caps. Unless I'm missing something in the video
As long as the valves' (tubes') cathodes are hot they still act as voltage amplifying stages and will drain off DC voltage from the reservoir cap onward down the rail draining filter caps on down to the lowest & last voltage node at the end of the rail.
This is a great tip. I use this method to power off my amps after playing ...because the caps will hold the HT for a long time, even after yanking the power. Great tip, but very risky leaving this out there for the 'Gotch-type' keyboard warriors, haha ...great stuff tho!
Based on what I studied in electronics at school, I assume that should be enough to discharge a working amp, but I never saw before a video saying this. I haven't done high voltage electronics in more than two decades, so I was wondering if I was correct. Thanks for this. I just have one question, this should hold true for almost every amp, rigth?
Your videos are great! thanks so much for the knowledge. I don't know if you've watched any interviews with Frank Zappa but you sound just like him Hahhah
Great video, if i may make a recommendation, get yourself a 1000 volt protective glove such as those that are sold by uvex, and then use your voltmeter to measure that the caps are of. With such protective gloves you really do not risk anything at all.
Hello from Canada,I have tried a new hand wired Fender Deluxe Reverb last night that retails for 3700$ CAD. Did you ever work on one of these? Are they really better than the reissues? I was wondering about what you show us about cheap condensers and all in the reissues. Do you have thoughts on those expensive Fender amps? I currently play with a Boogie mk5 combo that I really like but would not mind having a Deluxe also. Thx for your attention, Robert.
The '64 uses Sprague Atoms instead of IC filter caps. But that amp had its own set of issues, the wrong trem for that era of Fender amp, insulting fake blue molded coupling caps, and costs the same as a better quality early '70s original.
point of clarification 5:47 and 6:02 you say "yellow and green" but it looks like yellow and gray to me. I seem to recall you mentioning you have some color blindness before so understandable minor error. Great video, I learned from this and appreciate it.
Good question. I always used bleed resistors on my solid state amps. That's how I learned. But it would be interesting to find out. Unplug it from the wall while it's powered on and playing. No standby switch on solid state
My amp (Laney) cuts straight out if I do what you do but if I flip it to standby and leave the power on, the sound dies out like yours did in the video. Does that mean I should do this the other way round to you? By the way, great video. It's the first one that actually makes sense to me. Everyone else starts out by saying don't put your hands inside the amp until you've bled the high voltage caps and I think, "How am I supposed to remove the chassis and do that without putting my hands inside the amp!" Now you've answered my question. Sorry, one more question if you get this far - I can buy a 22k, 3W Metal Oxide Film Resistor locally - I'm guessing that would be fine too?
Well this was very specifically for Fenders. Not for all amps. WIthout seeing your Laney's schematic I couldn't tell you. Some amps use "standby" just for a speaker mute.
Another stellar video. I have a brand new 65 Princeton reverb FSR reissue (lacquered tweed and 12" speaker). Should I wait until the warranty has expired before opening her up to tighten all the recommended bolts? Also, is removing the chassis the same in tweed editions? I'm referring to the part where some foil sticks to the telex in the front of the amp, as you mentioned in previous videos. Thank you.
@@PsionicAudio sorry, one more question, in case I decide to hold off opening up the amp for awhile to tighten things up, if I understood your videos in this series correctly, it seems like I can remove the knobs and tighten all the input and volume jacks without having to remove the chassis, as well as the speaker and baffle nuts / bolts. To be clear, you never said or demonstrated that, but it doesn't look like I need access behind the pots or those jacks. Correct? Keep up the great work, your videos are fantastic.
You have to be careful that as you're tightening the hex nuts at the face plate, that the entire jack or pot isn't also rotating. If it is, you can twist and shear the internal wires (if they're "flown" to the circuit board) or - worse yet - shear the jack or pot right off the circuit board if they're board-mounted. Psionic opens the amp up so he can press or pinch the pot forward against the inside of the chassis using pinched fingers to keep it from rotating while tightening the exterior nut with a flat wrench. If you're not going to open the amp, you have to be extra-careful that you don't let the internal barrel or stem of the jack or pot rotate For jacks, a couple of folks have devised gripper tools to grip the jack barrel from the inside. You can grip and pull the jack barrel to the front while rotating the nut to tighten. For pots, I guess you can pull on the pot stem from the outside with your fingers while wrenching www.in2guitar.com/jack.html hazeguitars.com/blog/tighten-guitar-jacks-from-the-outside
@@PsionicAudio I wasn't referring to discharging capacitors. There are a lot of conversations as to why the standby switch exists. Put it in standby when you're not playing and the amp runs a lot cooler because the only heat generated is from the tube heaters. Otherwise you add the tube plate dissipation and everything else gets hot. When building or servicing an amp, I always shut the power off, then put the standby in play on my Super Reverb. On the Blues Junior you have no choice other than to shut it off and play it down as in your video.
Yes for both. Use your normal power on routine, wait until it makes sound, then play while and after you unplug the amp from the wall or power off using the switch (in which case then unplug from the wall). Then VERIFY.
Will doing this consistently also preserve the life of various components in the amp? Said another way, do you recommend this as a method to generally power down a DRRI for example? Or only if someone is going inside the amp to work on something? Thanks
Well, I won't go in an amp if there is more than 10VDC present. I'll keep discharging. But once it's below 3VDC I don't care if it's any lower than that. But that's in amps. A car battery is "only" 12VDC but it can kill you. But it provides a LOT more current than you find in guitar amps. I don't want to find out where the danger zone precisely starts. ;)
@@PsionicAudio fyi 12vdc is fine (can absolutely not kill you, unless you have some extremely serious heart conditions), with wet hands maybe you can feel 48Vdc. playing it safe however will avoid you any darwin awards.
you do NOT need to play the guitar, the hot tubes will conduct the current (bias current) through them, effectively discharging the caps (playing doesn't matter at all). But if you are going for a nice fade out tone, i guess go for it. Maybe it can help as a "confirmation" the caps are empty too, if you want to skip the volt measurement but i wouldn't recommend not testing for actual voltage.
Tubes cannot be relied upon to drain the caps fully. Short of using a large wattage resistor (which can be more dangerous for the untrained), playing to drain the caps is the best way to quickly and throughly drain them. BUT CONFIRM.
@@PsionicAudio Please enlighten me on how "playing" helps? i think i know electronics and tubes but i can always learn. Why is playing that discharges the capacitors and it is not the hot-tubes emitting electrons from their cathodes? Quick experiment to be sure, on an amp without capacitor bleed resistors and with either a solid state or directly heated rectifier flip the power switch on-off real fast, (pre amp tubes and power tubes still cold). Then connect your guitar and play for an hour (no heater power at all though), then with the most care measure the B+ (chances are it is even higher than normal B+). Then with an amp with a standby switch that cuts the circuit after the rectifier and not after the B+ capacitors, let it on standbly for 1 minute with hot tubes draining current out of the B+ capacitors. Then kill the power completely or pull the plug, voila the B+ capacitor should measure less than 5v DC (with no instrument ever connected to it throughout the process). If you do those 2 experiments and i am wrong please let me know, as i would really love to learn more. Thanks.
Because you would have to take the chassis completely out, flip it over and take off the doghouse cover to measure them. Lots of chances to potentially touch the wrong thing.
Because that would require refining the entire chassis BEFORE making sure things are safe. These measuring points are directly tied to the reservoir and screen caps.
If it has standby, power it on as usual, then take it out of standby. Then play and eiither power it off or (better) unplug it from the wall WHILE LEAVING THE STANDBY IN PLAY/OPERATE MODE.
@@PsionicAudioI was eluding to Princetons and Champs, which would be the same procedure but unplugging the amp from the wall instead of using the on/off switch while playing the guitar
Good info :) l do this every time I open up my amps. You really don’t even have to have a guitar plugged into it . It’ll discharge just the same. I’m my experience anyway.
@@weschilton "you can hear it to verify that its working." yes kind off, better check with a volt-meter in case the stand-by cuts after the filter caps, "the guitar helps it to discharge faster" absolutely not.
@@kapioskapiopoylos7338 No, it absolutely does. I've tested it. Maybe you should too. And it should go without saying that either way you test with a meter before going into an amp!
@@weschilton Maybe you missed something (bleeding resistors or residual heat or even old B+ capacitors with internal current leakage). on an amp without capacitor bleed resistors and with either a solid state or directly heated rectifier flip the power switch on-off real fast, (pre amp tubes and power tubes still cold). Then connect your guitar and play for an hour (no heater power at all though), then with the most care measure the B+ (chances are it is even higher than normal B+). Then with an amp with a standby switch that cuts the circuit after the rectifier and not after the B+ capacitors, let it on standbly for 1 minute with hot tubes draining current out of the B+ capacitors. Then kill the power completely or pull the plug, voila the B+ capacitor should measure less than 5v DC (with no instrument ever connected to it throughout the process). If you have no such standby switch, then let the amp get warm for 10 minutes and pull the plug, wait 1 minute, and measure B+, residual heat will drop it, again no instrument connected throughout the process. If you do those 2 experiments and i am wrong please let me know. if in doubt, manufacturers put filaments in the tubes for a reason, if electron emission by heat isn't it, please let me know.
I like to follow this by using an alligator clip with a load resistor from pin 1 of preamp tube 1 to ground and let it sit for a few minutes. Make sure that standby switch is on. Usually measure close to zero after this.
@@PsionicAudio , stray electrons actually do get trapped in the electrolyte between the capacitor foil layers, and so a filter capacitor that was drained and measured at "zero" volts can actually be measured again hours later and discovered to have built up a small residual charge again; rarely enough to give you a shock but possibly sufficient to damage a low-voltage semiconductor device. Not usually something to worry about safety-wise, nor would it be problematic when servicing a tube amp, but good to keep in mind when servicing solid-state equipment. A pair of say 10,000 mfd caps running at 80 volts can be drained, then measured again hours later only to find they've got maybe 10 volts stored on/built up in them, and enough current left to make a nice spark. It'll make you jump from the sheer surprise of it!
@@PsionicAudio , true, but for those who aren't aware of it, it will make them question their competence or their sanity ----- "what the heck? I thought I already drained those caps, didn't I ?". It's also enough residual voltage to cause a digital meter set to ohms to give weird readings if you're checking resistors for correct value/tolerance or when you're doing continuity tests while looking for bad connections.
No idea if this is entirely OK, but when I have to pull the chassis I often leave the power switch on and pull the AC plug from the wall and strum. I was unsure with some designs if turning the power switch off could prevent the power tubes from being drained.
Either will work. Pulling the plug is better just so you don't forget before pulling the chassis. I just couldn't do it easily at my bench while filming this.
I feel a little bad for those poor buffering caps that are doing their best to maintain working voltage only to realize there are no reinforcements on the way 😁
Not sure about this. You turned it off- so it went off. Circuit was broken. Certain tubes, capacitors, not tested in this video could still hold a charge. Believe that. The one node did not. Not sure playing did a thing either. Best tip for non-techs. Do NOT go inside your amp. A tech would go through your amp, tighten things up for probably $50 while you wait. Do that and demo some guitars and amps whilst you wait. Winning. I studied Elec. Engineering and I can tell you stories of people getting very messed up when amperage (not so much voltage) passes through the body. It is not pretty and effects are often permanent. Just don't do it. They make those warning stickers for a reason. And yes, for the love of god, a TECH will unplug the GD thing before fiddling around- that is not even up for debate.
Once you play with the power off to discharge the caps, UNPLUG THE AMP FROM THE WALL before going inside the chassis, Should have put that in the video.
Lyle, yeah..... I'll remember that the next time I shock the hell outta myself by forgetting to do that (I mean, haven't we ALL???). 🤣
It’s sad that you even have to clarify this.
great video, i want to clean my 90s twin and this will help me when i have to remove the chassis to clean the pots.
Having worked construction my whole life, and playing guitar, I learned that the neutral side of an outlet will shock you too, not as bad but not a good thing. Amps plugged in still get residual power from the neutral. Kinda like a back flow in reverse from the outlet
you are obviously a great tech so my endorsement means little there. What I can say however is over the last few weeks the quality of your youtube videos have gone up a lot. These last few have seemed to be more educational and the production has even increased- I realize being a tech first and a youtuber second- this may not be your overarching concern but it is appreciated for us out there who are learning some tips.
Thanks man. I do want the videos to be good. Not my main focus, but I am trying to step up.
agreed, huge step-up in quality content. Lyle, it's much appreciated!
Extremely well done!! I’ve learned so much about the good the bad and the ugly in amp builds and why they are that why!! Two thumbs way up!!
You're definitely a good man to explain safely how to remove a chassis to work on it
I've heard of this but never had to do it. As I never took my Deluxe Reverb RI apart when I had it. Your channel is probably one of the best amp channels on youtube. There will always be second guessers, it happens in any trade.
It is always reassuring and motivating to watch videos from like minded people with similar tastes, who also have an "old soul" to their character that help others understand often misunderstood concepts like the difference in an amps shortcomings, and what makes an amp "crap". you seem to maintain this mindset about a lot including yourself and other people and have a generally uncommon ability to see things for what they are, and for what they aren't. With that ability you don't seem to judge anything or anyone for more than they should reasonably be held responsible for and I respect the hell out of that. I love how your experiences in the shop with modern reissue amplifiers out of the Fender camp does not sway your love of that signature Fender sound has given you. To many people that would defy logic, but that just means that on a basic level they lack the experience and appreciation of something that impacts our lives in a unique and drastic way, which I think too many people nowadays have likely never experienced. I digress. There are quite a few aspects of your presentation and effort to educate that keep me coming back. You've been inspiring me to cautiously overcome my apprehensions about learning and understanding the complexity and dangers of amp circuits. I want to be able to keep the small collection I have functioning as they're designed, being respectful of the inherent dangers, so they can do their job of keeping a smile on my face for as long as I can play, hopefully passing on some of that joy to my daughter as she grows up as well. Cheers!
Another gem of a video. Cheers mate.
Another great video. Thanks for all you do.
Excellent, thanks for sharing this. Very useful!
I really enjoy your videos. As a long time amp tinkerer it's helped me better understand what I should and should not do myself. Glad I didn't have to learn that stuff the hard way.
Just one time, I decided to use the screwdriver to discharge the caps - I will never forget the SNAP and the pit it left on the screwdriver!!!! Serious stuff! Thanks for the video!
Hello, we were taught to do it the same way with Valve amps in the UK. Thanks for the reminder.
Thank you for such vital safety information.
Thx for posting this , very helpful information.
Thank you for the information, very helpful…
Now I can safely take my Deluxe in the tub with me. Less tingly now that I can discharge it.
In all seriousness, thanks for the context!
Lol.
🤣🤣🤣🛀🛀🛀
Thank You again Lyle, You may never know the lives You have saved, or at least dispensed with the cursing and flailing that accompanies a good shock.
Good Stuff Bro... You Sir are The Man and I Love Your Videos They Contain a Great Wealth Indispensable Knowledge.. Keep Up The Awesome Work 😎👊💯💯
totally digging the hand gestures.
Thanks, that's a great tip!
I was helping a friend wire a car audio power amp (500w rms) up once and he accidentally shorted the output terminals I was amazed how big of a arc resulted. And this amp had been sitting for years. Ever since I’ve had a healthy respect for large caps in general.
I Wanted to check if my 66 bandmaster had original filter caps. The amp still held on to 15 volts after this method. I continued by draining it slowly with the meter. The filter caps were original. Thanks for the video!
Cool tip. Interested to see that comprehensive video on the reissue blackface amps btw.
Thank you for showing this
This is the method I used when I went into my '67 Deluxe Reverb to replace those 55 year old filter caps. When I measured the voltage it was less than 1 volt anywhere in the amp. So I can confirm that this works. I haven't tried it with my Marshall JMP yet, but I will soon.
I still want to make a discharge tool with alligator clips and a big 200ohm 10-watt resistor... I have everything to make it, I just haven't had time to do it yet.
The higher you make the resistor , the LESS effective the tool . I usually stick to around 20-47 ohms .
I had forgotten about this-it doesn't pull it all out, but it makes it generally safe to do things like change jacks, replace the power cable, etc.
Also do this before you change or remove a tube.
I haven't worked on tube amps since the early 80's, and have forgotten all this stuff.
Very good information 😎👍👍
Thanks 😎👍❤🖖
Thank you !
Thank you for your wonderful videos. I've got a blues deluxe reissue (unfortunately, now that I've discovered your channel) that rarely gets used because it's just too dang loud if you want that edge of breakup sound, and perhaps it needs a tightening of bolts and screws. Just out of curiosity, what voltage would there be if you hadn't discharged the capacitors?
Thank you.
I never put my fingers in an amp that I'm not sure has discharged. I use someone else's fingers. I keep them in my little draw :-)
Rubber gloves
It's entirely possible that the information you presented in this video will have saved a life or two.
Some circuits I use to work on (not guitar amps) used to have bleed off resistors to discharge caps, or you had to take a probe and discharge each cap to ground.
Older Fender amps with filter caps wired in series for the first node usually had balancing resistors across the caps and these also functioned as bleeder resistors, though the ohms value was high enough that the caps didn't drain all that quickly.
I've been doing THAT for years !! Usually do it on the bench with a signal generator and raise the signal generator as I unplug the amp . I discovered this when I noticed how long after you unplugged a Dynaco pre amp that it would keep playing ......if you did it THAT way , by time you got the chassis open the quad cap was just about zero , doesn't hurt to check with an alligator clip and a resistor either though . Nice vid and GOOD point !!
Yea I've always done the resistor bleed down thing too. Some amps have them built in if I remember correctly. But always verify, especially with tube amps. It's good to see another way though 🎸
@@mikewithers299 You gotta' be careful with it , more common with TVs and Oscilloscopes but every once in a while it CAN creep back up again too ! I always check with a 10 ohm resistor and an alligator clip to be sure .
@frankporfidio9813 yes I had it happen on a couple amps that I was changing out filter caps on. I drained them and removed the resistor, got side tracked, came back to remove them and volts creeped back up again. Glad I checked again before unsoldering it!
I'm using two bulbs from fridge connected in series with two alligators clips, works fine every time without sparks and explosions ;))
I have a quick question! Would it be possible to custom build a point-to-point clone of a Mesa Dual Rectifier (2 channel)? From what I understand the preamp is similar to an SLO but the power amp is different. I wouldn't need the tube rectification and could forgo the "spongy" feature. I'm asking because I know how challenging mesa products are to maintain. Thanks, I love the channel & keep up the good work.
Oh course you can, its all about the time and expense
What do you use as a minimum resistor to discharge caps when they won’t bleed down?
My Fluke has a Low-Z input of 10k.
I’ve bled down little things (on container ships) with it, and actually tripped an alarm by pulling down a signal voltage.
Would it work for discharging a JCM 800 2204?
I could solder something together with something higher, I even have some 1000v junk leads that I could splice something into.
But if my Low-Z will handle it, it sure would be nice.
aren't those preamps tubes you're pointing at when you are talking about the 'subsequent' caps after the 'reservior' cap?
Thank you, great video. So if you have a bad power switch and unable to turn on the amp, then what do you do? You have to open the chassis to swap in a new power switch.
Then you take it to a tech. As I said in the video, this is a method for a working safe amp. This is not the only method, but unless you are a tech...
I suppose you could pull the tubes and stick a probe in the tube sockets before removing the chassis.
To discharge the filter caps you turn off the amplifier while strumming your guitar until it's dead sound but that doesn't mean their is still 350vdc charged voltage still holding storage on the filter caps. Unless I'm missing something in the video
What is the fully charged voltage on that rectifier reservoir node? Thanks for this safety vid.
Typically 400-440VDC with tubes present. Can be closer to 480VDC if the output tubes are not in the amp.
Does this method work for 65 Super Reverb Reissue?
is it good to shut the amp down this way untill the next gig
As long as the valves' (tubes') cathodes are hot they still act as voltage amplifying stages and will drain off DC voltage from the reservoir cap onward down the rail draining filter caps on down to the lowest & last voltage node at the end of the rail.
So the tubes have to be hot for this to work?
Will this also drain the filter caps in the dog house?
This is a great tip. I use this method to power off my amps after playing ...because the caps will hold the HT for a long time, even after yanking the power. Great tip, but very risky leaving this out there for the 'Gotch-type' keyboard warriors, haha ...great stuff tho!
Based on what I studied in electronics at school, I assume that should be enough to discharge a working amp, but I never saw before a video saying this. I haven't done high voltage electronics in more than two decades, so I was wondering if I was correct. Thanks for this.
I just have one question, this should hold true for almost every amp, rigth?
Usually. But we verify anyway.
At approximately 6 minutes you touch your probe to where a yellow and black wire join. You said yellow and green. Did you misspeak? Thanks
is there any alternative to this?
Your videos are great! thanks so much for the knowledge. I don't know if you've watched any interviews with Frank Zappa but you sound just like him Hahhah
Well, I love Frank but I don’t hear it.
But thanks!
Great video, if i may make a recommendation, get yourself a 1000 volt protective glove such as those that are sold by uvex, and then use your voltmeter to measure that the caps are of. With such protective gloves you really do not risk anything at all.
Hi, absolutely great informations, I have a '64 deluxe reissue which is hand wired, will this technic work the same to apply on the 64 reissue?
Yes.
@@PsionicAudio Thank you!
Hello from Canada,I have tried a new hand wired Fender Deluxe Reverb last night that retails for 3700$ CAD.
Did you ever work on one of these? Are they really better than the reissues? I was wondering about what you show us about cheap condensers and all in the reissues.
Do you have thoughts on those expensive Fender amps?
I currently play with a Boogie mk5 combo that I really like but would not mind having a Deluxe also.
Thx for your attention,
Robert.
The '64 uses Sprague Atoms instead of IC filter caps. But that amp had its own set of issues, the wrong trem for that era of Fender amp, insulting fake blue molded coupling caps, and costs the same as a better quality early '70s original.
If you're not servicing the amp, then is it important to discharge the caps? (To prolong their lifetime perhaps.)
Neat
point of clarification 5:47 and 6:02 you say "yellow and green" but it looks like yellow and gray to me. I seem to recall you mentioning you have some color blindness before so understandable minor error. Great video, I learned from this and appreciate it.
Someone else said brown.
I looked again and it's a greyish brown. Being next to that bright yellow made it look green to me.
Hi, does this technique work for solid-state amps also? Thanks!
Good question. I always used bleed resistors on my solid state amps. That's how I learned. But it would be interesting to find out. Unplug it from the wall while it's powered on and playing. No standby switch on solid state
My amp (Laney) cuts straight out if I do what you do but if I flip it to standby and leave the power on, the sound dies out like yours did in the video. Does that mean I should do this the other way round to you? By the way, great video. It's the first one that actually makes sense to me. Everyone else starts out by saying don't put your hands inside the amp until you've bled the high voltage caps and I think, "How am I supposed to remove the chassis and do that without putting my hands inside the amp!" Now you've answered my question. Sorry, one more question if you get this far - I can buy a 22k, 3W Metal Oxide Film Resistor locally - I'm guessing that would be fine too?
Well this was very specifically for Fenders. Not for all amps. WIthout seeing your Laney's schematic I couldn't tell you. Some amps use "standby" just for a speaker mute.
@@PsionicAudio Okay, thanks very much for your answer. I'll just be careful then!
Is this method the same for the Princeton Reverb amp, being a model without the Standby switch?
Okay then... Guess I'll have to shock myself to find out.
Another stellar video. I have a brand new 65 Princeton reverb FSR reissue (lacquered tweed and 12" speaker). Should I wait until the warranty has expired before opening her up to tighten all the recommended bolts? Also, is removing the chassis the same in tweed editions? I'm referring to the part where some foil sticks to the telex in the front of the amp, as you mentioned in previous videos. Thank you.
I would tighten all the hardware immediately to protect your investment. Shouldn't void the warranty. Removing the chassis should be the same.
@@PsionicAudio sorry, one more question, in case I decide to hold off opening up the amp for awhile to tighten things up, if I understood your videos in this series correctly, it seems like I can remove the knobs and tighten all the input and volume jacks without having to remove the chassis, as well as the speaker and baffle nuts / bolts. To be clear, you never said or demonstrated that, but it doesn't look like I need access behind the pots or those jacks. Correct? Keep up the great work, your videos are fantastic.
You have to be careful that as you're tightening the hex nuts at the face plate, that the entire jack or pot isn't also rotating. If it is, you can twist and shear the internal wires (if they're "flown" to the circuit board) or - worse yet - shear the jack or pot right off the circuit board if they're board-mounted.
Psionic opens the amp up so he can press or pinch the pot forward against the inside of the chassis using pinched fingers to keep it from rotating while tightening the exterior nut with a flat wrench.
If you're not going to open the amp, you have to be extra-careful that you don't let the internal barrel or stem of the jack or pot rotate
For jacks, a couple of folks have devised gripper tools to grip the jack barrel from the inside. You can grip and pull the jack barrel to the front while rotating the nut to tighten.
For pots, I guess you can pull on the pot stem from the outside with your fingers while wrenching
www.in2guitar.com/jack.html
hazeguitars.com/blog/tighten-guitar-jacks-from-the-outside
Another important use for a standby switch
How you get that from this video is beyond me. I was very clear that the standby is always left at Play. Never put it in standby to do this.
@@PsionicAudio I wasn't referring to discharging capacitors. There are a lot of conversations as to why the standby switch exists. Put it in standby when you're not playing and the amp runs a lot cooler because the only heat generated is from the tube heaters. Otherwise you add the tube plate dissipation and everything else gets hot. When building or servicing an amp, I always shut the power off, then put the standby in play on my Super Reverb. On the Blues Junior you have no choice other than to shut it off and play it down as in your video.
What about an amp that does not have a standby switch, like my 1966 Princeton?
Then it's even easier as you can't accidentally have it in standby.
Unplug. Submerge it in a pool, lake, or any other large body of water.
Would this also work for a Hot Rod Deluxe or Vox AC4?
Yes for both. Use your normal power on routine, wait until it makes sound, then play while and after you unplug the amp from the wall or power off using the switch (in which case then unplug from the wall).
Then VERIFY.
Will doing this consistently also preserve the life of various components in the amp? Said another way, do you recommend this as a method to generally power down a DRRI for example? Or only if someone is going inside the amp to work on something?
Thanks
Only for service.
@@PsionicAudio 👍
I have a Fender Blues Junior and it does not have a Standby. Does this method work with an amp that does not have a standby switch?
Standby is not part of this procedure. Notice it was in the Operate/Play position at all times. I even said "make sure you don't put it in Standby."
Would this work with a Pro Junior by switching it off at the wall or extension socket, as it only has a single on/off switch?
It works. Amps should never be in standby for this, so the Pro Jr just makes it easier for you.
@@PsionicAudio Excellent, thanks Lyle
6:03 - where those yellow and "brown" wires join.
To confirm the voltage has drained, it was at 2 volts and safe, where is the danger zone above that? Thx Lyle!
Well, I won't go in an amp if there is more than 10VDC present. I'll keep discharging. But once it's below 3VDC I don't care if it's any lower than that.
But that's in amps. A car battery is "only" 12VDC but it can kill you. But it provides a LOT more current than you find in guitar amps.
I don't want to find out where the danger zone precisely starts. ;)
@@PsionicAudio fyi 12vdc is fine (can absolutely not kill you, unless you have some extremely serious heart conditions), with wet hands maybe you can feel 48Vdc. playing it safe however will avoid you any darwin awards.
you do NOT need to play the guitar, the hot tubes will conduct the current (bias current) through them, effectively discharging the caps (playing doesn't matter at all). But if you are going for a nice fade out tone, i guess go for it. Maybe it can help as a "confirmation" the caps are empty too, if you want to skip the volt measurement but i wouldn't recommend not testing for actual voltage.
I think the point of playing was to demonstrate the caps discharging
@@ProSimex84 since it is an instructive video i suppose it could very much be the case indeed.
Tubes cannot be relied upon to drain the caps fully. Short of using a large wattage resistor (which can be more dangerous for the untrained), playing to drain the caps is the best way to quickly and throughly drain them.
BUT CONFIRM.
@@PsionicAudio Please enlighten me on how "playing" helps? i think i know electronics and tubes but i can always learn. Why is playing that discharges the capacitors and it is not the hot-tubes emitting electrons from their cathodes?
Quick experiment to be sure, on an amp without capacitor bleed resistors and with either a solid state or directly heated rectifier flip the power switch on-off real fast, (pre amp tubes and power tubes still cold). Then connect your guitar and play for an hour (no heater power at all though), then with the most care measure the B+ (chances are it is even higher than normal B+). Then with an amp with a standby switch that cuts the circuit after the rectifier and not after the B+ capacitors, let it on standbly for 1 minute with hot tubes draining current out of the B+ capacitors. Then kill the power completely or pull the plug, voila the B+ capacitor should measure less than 5v DC (with no instrument ever connected to it throughout the process). If you do those 2 experiments and i am wrong please let me know, as i would really love to learn more.
Thanks.
Why do you measure on the rectifier and screens instead of directly on the reservoir caps?
Because you would have to take the chassis completely out, flip it over and take off the doghouse cover to measure them. Lots of chances to potentially touch the wrong thing.
Because that would require refining the entire chassis BEFORE making sure things are safe. These measuring points are directly tied to the reservoir and screen caps.
Did I miss the part for if your amp doesn't have a standby switch? Everyone should know what the procedure would be but there maybe a few who dont.
If it has standby, power it on as usual, then take it out of standby. Then play and eiither power it off or (better) unplug it from the wall WHILE LEAVING THE STANDBY IN PLAY/OPERATE MODE.
@@PsionicAudioI was eluding to Princetons and Champs, which would be the same procedure but unplugging the amp from the wall instead of using the on/off switch while playing the guitar
5:00 Should it not have been unplugged as well?
Yes. Sorry, had thought I had made that clear. I'll put a pinned comment up on that.
Good info :) l do this every time I open up my amps. You really don’t even have to have a guitar plugged into it . It’ll discharge just the same. I’m my experience anyway.
True, but the guitar helps it to discharge faster, and you can hear it to verify that its working.
@@weschilton "you can hear it to verify that its working." yes kind off, better check with a volt-meter in case the stand-by cuts after the filter caps, "the guitar helps it to discharge faster" absolutely not.
@@kapioskapiopoylos7338 No, it absolutely does. I've tested it. Maybe you should too. And it should go without saying that either way you test with a meter before going into an amp!
@@weschilton Maybe you missed something (bleeding resistors or residual heat or even old B+ capacitors with internal current leakage).
on an amp without capacitor bleed resistors and with either a solid state or directly heated rectifier flip the power switch on-off real fast, (pre amp tubes and power tubes still cold). Then connect your guitar and play for an hour (no heater power at all though), then with the most care measure the B+ (chances are it is even higher than normal B+). Then with an amp with a standby switch that cuts the circuit after the rectifier and not after the B+ capacitors, let it on standbly for 1 minute with hot tubes draining current out of the B+ capacitors. Then kill the power completely or pull the plug, voila the B+ capacitor should measure less than 5v DC (with no instrument ever connected to it throughout the process).
If you have no such standby switch, then let the amp get warm for 10 minutes and pull the plug, wait 1 minute, and measure B+, residual heat will drop it, again no instrument connected throughout the process.
If you do those 2 experiments and i am wrong please let me know.
if in doubt, manufacturers put filaments in the tubes for a reason, if electron emission by heat isn't it, please let me know.
Id always heard that not using Standby first eventually damages an amp..... ?
Most of the time, no. And never with an amp with a tube rectifier. But watch the video linked at the end of this one for more on that.
Why do you have to keep playing while they dischargeor was that only to illustrate to us that they were discharging?
They won't discharge unless you play. At least not reliably/quickly.
It's the playing that drains the caps.
@@PsionicAudio Thanks.
I like to follow this by using an alligator clip with a load resistor from pin 1 of preamp tube 1 to ground and let it sit for a few minutes. Make sure that standby switch is on. Usually measure close to zero after this.
Why ?? 2.7 v is not even going too tickle ur balls guy...ffs
Can they sometimes recharge back while you are working?
No. They cannot get DC from the ether...
@@PsionicAudio , stray electrons actually do get trapped in the electrolyte between the capacitor foil layers, and so a filter capacitor that was drained and measured at "zero" volts can actually be measured again hours later and discovered to have built up a small residual charge again; rarely enough to give you a shock but possibly sufficient to damage a low-voltage semiconductor device. Not usually something to worry about safety-wise, nor would it be problematic when servicing a tube amp, but good to keep in mind when servicing solid-state equipment. A pair of say 10,000 mfd caps running at 80 volts can be drained, then measured again hours later only to find they've got maybe 10 volts stored on/built up in them, and enough current left to make a nice spark. It'll make you jump from the sheer surprise of it!
That's a small fluctuation.
@@PsionicAudio , true, but for those who aren't aware of it, it will make them question their competence or their sanity ----- "what the heck? I thought I already drained those caps, didn't I ?". It's also enough residual voltage to cause a digital meter set to ohms to give weird readings if you're checking resistors for correct value/tolerance or when you're doing continuity tests while looking for bad connections.
No idea if this is entirely OK, but when I have to pull the chassis I often leave the power switch on and pull the AC plug from the wall and strum. I was unsure with some designs if turning the power switch off could prevent the power tubes from being drained.
Either will work. Pulling the plug is better just so you don't forget before pulling the chassis. I just couldn't do it easily at my bench while filming this.
@@PsionicAudio Thanks! Love the channel.
Don't you mean yellow and gray wire.
I feel a little bad for those poor buffering caps that are doing their best to maintain working voltage only to realize there are no reinforcements on the way 😁
If one does not understand this video it is best not to put their finger in an amp IMHO.
I agree. I try to be clear, but there are some Darwin Award nominees out there...
@@PsionicAudio but those existed for ever and they will keep doing so untill they get their reward.
Color blind? 5:45
Not being a troll. Just curious.
I was thinking the same thing.... its grey not green.
Not sure about this. You turned it off- so it went off. Circuit was broken. Certain tubes, capacitors, not tested in this video could still hold a charge. Believe that. The one node did not. Not sure playing did a thing either. Best tip for non-techs. Do NOT go inside your amp. A tech would go through your amp, tighten things up for probably $50 while you wait. Do that and demo some guitars and amps whilst you wait. Winning. I studied Elec. Engineering and I can tell you stories of people getting very messed up when amperage (not so much voltage) passes through the body. It is not pretty and effects are often permanent. Just don't do it. They make those warning stickers for a reason. And yes, for the love of god, a TECH will unplug the GD thing before fiddling around- that is not even up for debate.