The #1 Mistake You're Making with Dim Bulb Testers - Don't Make It Again!

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  • @kowaltoboggan
    @kowaltoboggan Год назад +23

    I m compelled to thank you for taking the time and making the effort to create videos like this. You don’t need to, but because you do many of us have opportunity to learn. Thank you!

  • @WC0125
    @WC0125 Год назад +4

    I appreciate the information videos such as your share with many new to electronics. In truth a huge mistake for many is not reading the service information and making sure the input line voltage to the device is what it should be when making any post repair adjustments, alignments, final measurements, etc. The DBT is absolutely an excellent aid for repair but should never be left in circuit once you get to the adjustment and alignment stage. It lowers the input voltage and current and can make adjustments way off even in equipment with modern design power supplies. With any DBT you should have more than various wattage bulbs to use. You should use one sized to the input power rating of the equipment you are working on. Smaller ones are ok but they may drop the input line voltage to the point the device may not come on even for initial testing.

  • @vsalasarcr
    @vsalasarcr Год назад +4

    Hello, I hope you are well, once again thank you very much for all the learning you give us.

  • @CraigHollabaugh
    @CraigHollabaugh Год назад +8

    For me, I usually don't figure it out until after I blow the new transistor. That's why I order spares. Thanks from the dim bulb in Colorado.

    • @vintageaudioaddict
      @vintageaudioaddict  Год назад

      I've done it plenty. Thanks for watching.

    • @fullwaverecked
      @fullwaverecked Год назад +1

      Hey Craig! Cheers from the dim bulb in Utah! 😎🤟🤓

    • @CraigHollabaugh
      @CraigHollabaugh Год назад +1

      @@fullwaverecked howdy

    • @Poppinwheeeeellllllieeeeez
      @Poppinwheeeeellllllieeeeez Год назад

      You are not the only one. When I hear the little click when it shorts it is usually followed immediately by a four letter word.

    • @fullwaverecked
      @fullwaverecked Год назад

      ​@@PoppinwheeeeellllllieeeeezSnap!

  • @stevedonkers9087
    @stevedonkers9087 Год назад +1

    Subbed. This is the exact sort of video I like, someone that's had the problem, figured out the solution and doesn't mind sharing. I'll be building a dim bulb soon (I fried a vintage heathkit function generator) and this drawback is definitely something I'm happy to be aware of beforehand. Thank you, sir!

  • @peterlarkin762
    @peterlarkin762 Год назад +3

    Great info here. Wish this video was around years ago, would have saved me a steep learning curve. Ive been caught out with biasing amps while plugged in to a limiter. That can be damaging on old amps, they can overheat if the bias is too high.

  • @g.fortin3228
    @g.fortin3228 Год назад +8

    Love the insight and experience here! You have helped me understand things quicker and taken some of the learning curve time out . Thank you Sir ! :- )

    • @vintageaudioaddict
      @vintageaudioaddict  Год назад +3

      Your welcome and thanks for watching. I'm glad that the video's help.

  • @Mike_S_Swift
    @Mike_S_Swift 3 месяца назад

    Glad I saw this video of yours. I’m getting ready to put my dim bulb tester together for a guitar amplifier kit project I’m doing this winter. I’m sure I would have tried to bias the power tubes with the dim bulb tester. Thanks so much for sharing!!

  • @James_Bowie
    @James_Bowie 11 месяцев назад +2

    TIP: Plug the dim bulb into a kill-a-watt type meter and keep an eye on that, too. Whenever I adjust bias, as well as the DC voltage, I also watch the input watts vs the rated watts of the amplifier.

  • @fullwaverecked
    @fullwaverecked Год назад +5

    Ive added a rocker switch that glows red (STOP) to my DBT for convenience, to bypass the DBT, and i also added a red and a green indicator lamp so I'm more certain i don't damage the DUT. One can never be too safe, but just like getting out of bed in the morning, there are no guarantees... Cheers!

  • @fisherhutchens9452
    @fisherhutchens9452 Год назад +1

    I had the EXACT experience yesterday with my dim bulb tester. I was working on a Hafler DH220 and was plugged I to my dim bulb tester. The bias current was a little low since the AC power was a little low due to the voltage drop through the bulb. I had to redo the adjustments.

  • @giuseppevitucci4641
    @giuseppevitucci4641 Год назад +3

    Thank you for your detailed explanation. Much appreciated. I look forward to each of your videos.

  • @eadiew
    @eadiew Год назад

    Thank you for this video. I’m new to vintage electronics, and it seemed gospel to always use a dim bulb tester, so it’s great to see when using one is *not* appropriate.

    • @ΠάριςΑζής
      @ΠάριςΑζής 9 месяцев назад

      This jig should only be used during troubleshooting. After confirming that the repair is done successfully the equipment shoulld be powered directly from mains.

  • @DCDura
    @DCDura Год назад

    Great information. Annoying music is not needed.

  • @groovy1937
    @groovy1937 Год назад

    Great explanation on dim bulb tester and troubleshooting!

  • @morrisonAV
    @morrisonAV Год назад +1

    Thanks so much for this. I learned from lots of folks on AK to remove the DUT from the dim bulb before making any adjustments so I completely understand your point. One thing I could never wrap my head around was what wattage of bulb to use. It seemed like most were using 60 to 100 watts but I never understood why. Greetings from up the coast in St. Pete!

    • @vintageaudioaddict
      @vintageaudioaddict  Год назад

      Your welcome and thank you for watching. I thought it was worth mentioning. It's an easy mistake to make when you are first using a DBT.

    • @Rx7man
      @Rx7man Год назад +1

      it's going to vary a bit depending on the type of equipment you're working on, but you want a good amount of current, but not enough to blow things up. if you're working with a device that takes 100w peak you might want to use a 40w bulb, while the 40w bulb isn't going to be enough if what you're working on takes 1000w, or if it powers up the device, the bulb might stay fairly lit fooling you into thinking there's a problem when there isn't one

  • @Robert.Chauval
    @Robert.Chauval 4 месяца назад

    Nice job explaining that a DBT puts your DUT in a non optimal self bias configuration and caution is needed.
    I have a 3 way switch that allows me to step up to 3 bulbs in parallel progressively upping the current to the DUT and when im happy i have a TEST-BYPASS switch that can power the DUT without the DBulbs in cct.

  • @COFFEE-e3p
    @COFFEE-e3p 11 месяцев назад

    THANK-YOU SO MUCH FOR SHARING YOUR KNOWLEDGE SIR !! YOU DA MAN , STAY AWESOME !!

  • @g.fortin3228
    @g.fortin3228 Год назад +1

    Was wondering what size bulb.. had paused the video near the end to get some food.. I see you gave the details thank you !!

    • @vintageaudioaddict
      @vintageaudioaddict  Год назад +1

      Your welcome and thanks for watching. 100 watt usually works well for most equipment.

    • @g.fortin3228
      @g.fortin3228 Год назад

      @@vintageaudioaddict glad i have one..they are becoming hard to find !

  • @vladimirsalinas442
    @vladimirsalinas442 5 месяцев назад

    Thanks for this useful and important information.

  • @Daltondoubledeuce
    @Daltondoubledeuce Год назад +1

    Chris, can u cover isolation transformer? So confusing about the ground and it being truly isolated. Thx.!

  • @curtchase3730
    @curtchase3730 Год назад +3

    Fully agree with all your procedures. I only use a dim bulb to find a catastrophic failure and fix it. I also will use my dim bulb when powering up my vintage amps if they have been sitting unused for many month's or years. I will run them through a 300 watt bulb. My theory is doing that the amp will not be "shocked" back to life. It allows a more gradual charging of filter caps. What about using a dim bulb for equipment with switching power supplies? Instead of an old linear PS that just says "here is all the power/voltage you will even need, so just take what you need". A switching PS will consume more or less current from the mains to maintain a regulated output "on the fly". Unlike a conventional old school power supply, the SMP only stores a small reserve of power, but relies on a good power source to grab the power it needs. If the mains voltage drops, the SMS will draw more current to compensate for drop to maintain output voltage. I feel a dim bulb inserted into the supply line could cause a failure because the poor SMS will try everything to get the output where it is supposed to be! That means a huge current flow when it is undervoltaged. I feel something will pop?

    • @vintageaudioaddict
      @vintageaudioaddict  Год назад

      Thanks so much for sharing. Using a DBT takes some experience because of the differences between the equipment and the bulb wattage used.

    • @Rx7man
      @Rx7man Год назад

      Another electronics channel I follow does a lot of ATX power supply repairs and uses a DBT all the time on them.. Really good channel as well www.youtube.com/@LearnElectronicsRepair

    • @ΠάριςΑζής
      @ΠάριςΑζής 9 месяцев назад +1

      The wattage of the lamp should be less than or equal to the wattage of the device under repair. Higher than that offers no protection.

  • @tim9778
    @tim9778 Месяц назад

    Hi Chris. I would agree with you that( just like with everything else in life) the “ dim bulb” is not a universal panacea. I have had a couple of things smoke the transformer even with the bulb in circuit.
    Re. comments on idle current, while what you say is perfectly valid my “variable auto transformer “( mine is actually a “ Regulac, but I guess the best name was already taken) can give about 260 volts out for a 230/40 volt input.
    I can wind up the voltage to compensate for the D.B and still have it in circuit. Handy in case I slip with the probes! Anyone who has ever done that on a Quad 405 and blown the final o/p transistors will know exactly what I mean.

  • @DuoJet63
    @DuoJet63 9 месяцев назад +1

    Very useful information

  • @hlash99
    @hlash99 7 месяцев назад

    wonderful video, I learned a lot! does a 100W bulb work on vintage monster receivers too, something with a 560W power supply for example?

  • @CrispyCircuits
    @CrispyCircuits 11 месяцев назад

    I noticed that you were using tamper-resistant outlets. I was watching some electrician videos and I realized that I could easily have wire bits and components fall into the receptacles, so I bought that type.

  • @m.a.quashem1989
    @m.a.quashem1989 Год назад +1

    Many many thanks for the video.

  • @bmboldt
    @bmboldt Год назад +3

    I was working on an NAD receiver and was getting 3 or 4 V DC offset when using my dim bulb tester. The bulb would stay bright from what I remember. Without a dim bulb I was getting millivolts and no issues. I think I was using a 40W bulb. I went to a larger bulb and everything was fine. For some reason the smaller bulb wasn't allowing the receiver to power up correctly and wreaking havoc with the DC offset.

    • @vintageaudioaddict
      @vintageaudioaddict  Год назад +1

      Thanks for sharing. I have had a few issues but generally the 100 watt works for me with most equipment. The only issue I remember having with the 100 watt bulb was my Sansui BA-5000 power amp. It would not even power up on the dim bulb tester until I installed a 200 watt bulb. Not sure why that would happen? But it did.

    • @Hyxtryx
      @Hyxtryx Год назад

      @bmboldt " I went to a larger bulb and everything was fine. For some reason the smaller bulb wasn't allowing the receiver to power up correctly"
      This is the reason: watts = volts ^ 2 / ohms. So a higher watt bulb means it has a lower resistance. volts = amps * ohms. So a lower resistance bulb means less volts lost across it, meaning more of the 120V from the wall outlet makes it to your receiver. If your receiver doesn't have enough volts, it's not going to power up correctly. The more current your item draws under normal operation, the more volts you'll lose across the bulb. So higher current items that need an accurate power supply will need a higher watt bulb.

    • @CrispyCircuits
      @CrispyCircuits 11 месяцев назад

      I am just figuring out a wiring diagram for my first DBT. I know where to get some 200 watt incandescent bulbs. I'll go get them for something that needs extra power. I should have bought them when I was there, but I had a mountain of things I was buying

    • @ΠάριςΑζής
      @ΠάριςΑζής 9 месяцев назад

      The test lamp wattage should be less than or equal to the device power, but not higher than that because in this case it offers no protection.

  • @flashbizz6110
    @flashbizz6110 8 месяцев назад

    Hi. Can i use a 130v 100watts bulb for dimbulb tester? Thanks

  • @nonsuch
    @nonsuch Год назад +1

    A 100w bulb is a little low for powerful amplifiers. I use a 300w clear glass bulb so, of course it lights it up bright when there's a dead short but, I still can see the dimmest of illumination if there's an issue without turning the shop lights off.

    • @fisherhutchens9452
      @fisherhutchens9452 Год назад +1

      I have 2 150w clear bulbs in parallel.

    • @ΠάριςΑζής
      @ΠάριςΑζής 9 месяцев назад +1

      Directly related to your text, is my comment above in the pile, regarding the proper wattage of the test lamp.

    • @Robert.Chauval
      @Robert.Chauval 4 месяца назад

      ​@@fisherhutchens9452i have 3 clear with a triple switch. Can proggessively step from 1 to 3 in parallel.. then a bypass switch when im happy all is ok for 100% mains power.
      100% agree the clear bulbs help a lot to identify trickle currents that you wont see with opaque bulbs

  • @tomasw6985
    @tomasw6985 5 месяцев назад +1

    Tantalum caps suck. I always check them. I had an old Marantz that almost every one of them turned into resistors instead of caps.

    • @Robert.Chauval
      @Robert.Chauval 4 месяца назад

      Totally agree.. ive been calling them TANTRUMS since the 1980s.. they are far to often used in the wrong places like low impedance power rails.. Tantrums simply cannot tolerate low Z voltage surges. Ive literally seen them smoke and explode when powering up. They are perfectly happy at the end of a power rail immediately next to the PS pins of an ic where they can provide HF bypassing safely.
      The 1uF 35V Tantrum located in the PSU should be replaced with an electro or a film or an MLCC ceramic. Tantrum begone....

  • @michaeldoherty7434
    @michaeldoherty7434 13 дней назад

    The problem with using the dim bulb unit with the Pioneer is the bulb drops voltage when it’s glowing; the more it glows the higher the voltage drops. I guess that the input voltage to the Pioneer wasn’t high enough to allow the internal power supplies to output the correct voltages and that resulted in the bias current being wrong. I’d always check the internal voltages before taking any measurements.

  • @bisarowood
    @bisarowood 9 месяцев назад

    great info thanks

  • @danmcbmusic
    @danmcbmusic Месяц назад

    Short circuit is common failure on tants. Always change them out if used for decoupling

  • @Gabrielishere
    @Gabrielishere Год назад +1

    Oh man I got lucky then... I was doing exactly what was described in this video NOT to do, and I did not blow up my Marantz 2325. New to doing this, and definitely won't do that again. Thanks!

    • @vintageaudioaddict
      @vintageaudioaddict  Год назад +1

      Your welcome and thanks for watching. You should probably check your idle current again off the dim bulb tester.

    • @Gabrielishere
      @Gabrielishere Год назад

      @@vintageaudioaddict Did check it off of house power, but then I went to put a new relay in and lifted some traces... since I'm fairly new, I dropped it off at a tech to repair the lifted pads and get it working again, then will slowly recap the boards with a desolder and solder iron.

  •  Год назад

    What is the advantage of using bulbs instead of testing devices with ammeters? As far as i know you combine isolation transformer with a variac and while you raise the voltage slowly, you keep an eye on the amps. Dim bulb testers are better?

    • @CrispyCircuits
      @CrispyCircuits 11 месяцев назад

      You can see the changes really fast without thinking. If you want to use an ammeter, be sure to get an analog one. You could definitely use a high wattage resistor plus an ammeter. But bulbs are cheap. Throw in a digital ammeter if you just want the data. It's possible that a wirewound resistor could have an inductive effect. I have two 8 ohm non-inductive resistors. That lets me get 8 ohms, 4 ohms if parallel and 16 ohms if in series. These would be good for speaker dummy loads. They are not cheap. I have a goofy lamp that has colored night light incandescent bulbs that I may add to show if it is connected to the mains directly or if not. I haven't decided yet.

    • @ΠάριςΑζής
      @ΠάριςΑζής 9 месяцев назад

      The variac, if used alone, will blow up your device if it reaches the critical voltage. The lamp prevents this effect. It acts as a PTC thermistor.

  • @yambo59
    @yambo59 6 дней назад

    I need to build a dim bulb tester myself for an upcoming project, but where am I supposed to get a 100 watt incandescent bulb now-????

  • @anoushan
    @anoushan Год назад

    Hi,
    I got a powered mixer 110V 700W power consumption,
    I powered it up with a dim bulb tester with 100W bulb. When press power, the dim bulb flashes on and off. You think the dim bulb is limiting the current stopping the mixer to start up.

    • @ΠάριςΑζής
      @ΠάριςΑζής 9 месяцев назад

      Yes. (If you want to know why, you can see my comment above in the pile).

  • @fullwaverecked
    @fullwaverecked Год назад +1

    There must be a good reason, but im not ambitious enough to Google it, so while I'm here, why do we still use tantilums? Thanks!

  • @dougjane64
    @dougjane64 9 дней назад +1

    You have made some mistakes here. First, you had a faulty transistor, but you already had previously had this unit on. So you could have plugged it in and nothing else would have happened. You should have trouble shooted the power supply with another supply feeding in at the bridge rectifier.

  • @YTANDY100
    @YTANDY100 Год назад

    if the old Q620 was shorted why no light ?

    • @badenmelhuish3215
      @badenmelhuish3215 8 месяцев назад

      Hi, I was thinking that too. The only thing I can think of is if Q620 was open cct, and the continuity beep from the meter was when he tested between the tab and the center pin. Cheers.

  • @dougjane64
    @dougjane64 9 дней назад

    As to the idle current comment, the dim bulb tester is there to save you from catastrophic failures. Once the amp is running, remove the dim bulb tester before checking your idle current.

  • @ΠάριςΑζής
    @ΠάριςΑζής 11 месяцев назад +1

    The wattage of the bulb should always be less or equal (but not greater than) the wattage of the equipment under repair. Otherwise it doesn't offer any protection. This means that a 100W lamp cannot be used for any repair. Therefore many lamps of different wattage should be available for this test jig...

  • @coalthedergsune
    @coalthedergsune 2 месяца назад

    I have a rotary switch that goes up in increments of 15 watts on mine

  • @inlandbott
    @inlandbott Год назад +1

    Can u turn the music down a tad:)

  • @genehammond7239
    @genehammond7239 Год назад +1

    👍👍

  • @COFFEE-e3p
    @COFFEE-e3p 11 месяцев назад

    ONE OF A MILLION QUESTIONS , ISN,T THAT THE PURPOSE OF A VARIAC ??

    • @ΠάριςΑζής
      @ΠάριςΑζής 9 месяцев назад

      Yes, but it will still blow up your (still defective) device when reaching the critical voltage. The lamp prevents that by lighting up.

  • @michaelbarras6950
    @michaelbarras6950 Год назад +10

    Common sense tells you, if you have a dim bulb tester hooked up to a piece of equipment that you're testing for shorts, you are limiting current!
    Why in the world would anyone adjust current flow with a dim bulb tester connected? lol
    If you can't figure that one out, I guess you need not be repairing electronics right!? There is no room for mistakes like that!

    • @vintageaudioaddict
      @vintageaudioaddict  Год назад +1

      Thanks for commenting and for watching.

    • @jimb032
      @jimb032 Год назад +1

      I tend to agree. I use it in combination with a Variac. Then when the unit starts, I bypass the dim bulb immediately. I put an abnormally small fuse on the Variac for protection.
      The dim bulb needs removed immediately because it can glow without you tend to notice.

    • @Gabrielishere
      @Gabrielishere Год назад

      Starting off in this hobby, I blew up some output transistors and the lightning strike took out random things on the left amp board on a McIntosh by shorting with my multimeter, and it ended up costing me a pretty penny to get right again... After that, I was so nervous to do anything, that I kept my components on a dim bulb for everything, so for me, the fear was outweighing the logic for a bit, but now that I have good grabbers, I can think clearly again. Apprenticeship helps greatly, to flatten the curve a bit.

    • @Poppinwheeeeellllllieeeeez
      @Poppinwheeeeellllllieeeeez Год назад +1

      What if you forget? Anything can happen if you are fatigued or distracted. No one is infallible.

    • @Hyxtryx
      @Hyxtryx Год назад

      Haha, yes! On the one hand you have audiophiles who are worried about what power cord to use for best sound reproduction, and on the other you have techs (hobbyists?) adjusting audio equipment with a light bulb in series with the power line! 😆

  • @dbaider9467
    @dbaider9467 Год назад +1

    Newbie question: must the bulb be incandescent?

  • @Homer19521
    @Homer19521 Год назад +1

    "The #1 Mistake "You're" Making...?????" "You're" ??? Come'on man!!! That's why you have a bypass switch on the DBT. Only someone who is a dim bulb would do that. You lost me on that one.

  • @geirendre
    @geirendre Год назад

    Why are you asuming people are making this mistake? I have never heard that happend.

    • @vintageaudioaddict
      @vintageaudioaddict  Год назад +5

      I am not assuming anything. I am trying to prevent inexperienced people from making a mistake.

    • @geirendre
      @geirendre Год назад +1

      @@vintageaudioaddict "Mistake You're Making" ...Aren't you assuming here?

    • @Gabrielishere
      @Gabrielishere Год назад +3

      @@geirendre I was one of the people who made that mistake. Why are you assuming that it has "never" happened, just because you haven't heard of it happening?