Might have ****ed something up

Discussion in 'Amp Tech Center' started by JeffBro, Aug 29, 2020.

  1. JeffBro

    JeffBro TDPRI Member

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    3E162A64-FCBD-4233-933A-CA4BB23A10AC.jpeg A78213B6-D052-442F-B0D6-C1114239A4DD.jpeg

    I just replaced all the caps and did some mods on my Super6... purchase some new tubes and played it to test it and it worked fine, then got busy and came back couple if days ago and now channel 1 does work, there is a huge buzzing and overall I think I did something bad... how bad, I’m not sure.

    the power tubes have 2 large black spot on them? Did I bias the amp incorrectly and destroy the tubes?
     
  2. stantheman

    stantheman Doctor of Teleocity

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    I don’t think so.
    That buzzing might be a cracked tube retainer.
    Happened to me eons ago with a Silverface Deluxe reverb
    If I remember it had a hairline crack in the porcelain
    and raised Cain as soon as it warmed up.
     
  3. dan40

    dan40 Tele-Afflicted

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    Try the amp in a dimly lit room. If you see the plate structure inside of the tubes begin to heat up and glow orange, shut the amp down quickly. This would be a sign of redplating and it indicates a problem with the tubes themselves or the bias circuit. Normal filament glow inside of the tubes is fine but the actual metal plate structure inside of the tube should not show any signs of redplating when the amp is working properly.
     
  4. hepular

    hepular Tele-Meister

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    do you feel competent to measure the relevant bias voltages to check for yourself?

    have you double-checked all of your mods to make sure the solder's good, the component values are correct & connected correctly?

    trust me (& most of us, i'd guess) it's pretty easy to make that one tiny screw up with largish consequences.
     
  5. JeffBro

    JeffBro TDPRI Member

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    I can upload some photos of the wiring/inside... I double-checked all of my work

    I think my amp just has a balance bias, but maybe I'm wrong...

    wanna give me a walkthrough on how you measure the bias voltages? There seems to be a lot of different ways online

    IMG-0943.jpg IMG-0944.jpg
     
    Last edited: Aug 29, 2020
  6. kbold

    kbold Tele-Afflicted Silver Supporter

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    Which caps?
    Did you discharge high V caps before work, and if so, how?
     
  7. 24 track

    24 track Doctor of Teleocity Silver Supporter

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    those black spots on the tubes are where they set the vaccuum in side the tube during manufacture , if the spots were white it would mean you have a vaccuum leak and the tubes would be no good.
     
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  8. JeffBro

    JeffBro TDPRI Member

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    so that means the tubes are good? I might just have to have an amp tech go through it and tell what I did incorrect
     
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  9. JeffBro

    JeffBro TDPRI Member

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    why do you ask?
     
  10. 24 track

    24 track Doctor of Teleocity Silver Supporter

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    take it to your local music store (GC ) or what ever and ask them to try a couple of new tubes to see if it fixes the problem , the tubes may be pooched or not and it may be a simple fix

    try replacing the power tubes one at a time to see if the noise moves with the tube exchange , if the noise follows one tube only then that tube is pooched, if the amp works with one tube in , try that tube in each socket if that cleans up the noise in that chanel then you know you have a bad tube

    reset your other tubes (12AX7'S) to make sure they are seated properly, also try to take some De-Oxit and a q tip and clean the pins on your tubes to remove any oils or corrosion

    also make sure the correct tubes are in the correct sockets
    simple stuff to try before you take it in for service
     
    Last edited: Aug 29, 2020
  11. 24 track

    24 track Doctor of Teleocity Silver Supporter

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    there are voltages in side the amp that could kill you, flat out , even if the amp is unplugged, those 500 volt filter caps carry 500 volts and can definately make your day go very bad very fast, how you discharge those caps is an indicator to transient voltages retained , to test to see if there any voltages present , attach the black (-) lead of your multimeter to the chassis and the positive red lead to the (+) side of those high voltage filter caps put you multimeter on DC voltage, that voltage is resident in those caps and can kill

    also did you install those caps in the correct orientation ? positive to positive ,neg to neg?
     
  12. Milspec

    Milspec Poster Extraordinaire Silver Supporter

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    I made the same conclusion awhile back only to discover that some tube builders placed the getter on the side of the glass instead of at the top. If you had a top getter, you would see silver inside the top...I don't see it in your picture, so the spot you are looking at is likely the side position getter. In other words, tubes are probably fine and not the problem.

    That said, you really do need to careful working inside an amplifier if you are not experienced. A mistake can be quite deadly.
     
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  13. JeffBro

    JeffBro TDPRI Member

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    yeah, I have the right tubes in the right sockets... I'm going to power the beast up again and see if the plates glow. Could not be biased correctly, wasn't sure if someone just looking at it knew if I have a balance or regular bias control
     
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  14. JeffBro

    JeffBro TDPRI Member

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    yeah, I replaced the caps at the bottom, I just discharged them and put new ones in... it is an important thing to know because you can hurt yourself
     
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  15. 24 track

    24 track Doctor of Teleocity Silver Supporter

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    I just did a repair on a fender supersonic 22 , one chanel worked one didnot after finding 4 relays in the circuit with corrosion on the contacts I resoldered them back in and did the tube swap and the both chanels came up only to discover the reverb transformer was cooked and posibly one of the transistors was gone as well , but it took all of the tests i mentioned to fix the issues ,
     
  16. Rich_S

    Rich_S Friend of Leo's Silver Supporter

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    Come on, people. There’s a bunch of wild-ass guesses here that ignore a major piece of the puzzle.

    OP said channel 1 does not work and there’s a buzzing. Clearly, if channel 1 doesn’t work and channel 2 does, then the problem is not in the power stage. Look at components in the channel 1 signal path. It could be a bad tube or cracked socket, but it’s more likely (if you recently changed caps in channel 1) to be related to a cap. Make sure you didn’t forget to solder a connection. Chop-stick all your re-soldered connections to see if any are noisy or cracked. Re-flow any suspect connections.

    This is not intended to reflect on your workmanship, it’s just that any new problem is most likely to be caused by the most recent change in the amp, i.e. the new caps. If some other problem cropped up at the same time, it’s a coincidence. Not impossible, but less likely.

    On a most-likely unrelated issue, it’s always good the check/adjust bias whenever you change output tubes. Those tubes don’t look bad to me, but make sure they’re not red-plating and check the bias. However, even if the bias is off, it would not cause only channel 1 to stop working.
     
    Last edited: Aug 29, 2020
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  17. JeffBro

    JeffBro TDPRI Member

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    Rich, thx for the reply... the channel did work at first, then when I turned it on again it didn’t. Thx for the advice, I’ll recheck the connections on the caps again, which caps do you think it might be? [did u see the photo above?]
     

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  18. JeffBro

    JeffBro TDPRI Member

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    I played it around it a bit more and the plates are glowing red on the three blue ones. I adjusted the bias and on those 3 the are still glowing red

    I’ll contact the tube supplier and see what they have to say
     

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  19. kbold

    kbold Tele-Afflicted Silver Supporter

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    You answered a question with a question (which is not an answer).
    It's more polite to just answer the question (otherwise some may be inclined not to reply).

    The reason I ask: some people like to short out the caps (big spark) to discharge.
    This can damage caps, or rectifier diodes. If 1 or more rectifier diodes goes short cct, this will cause loud transformer buzzing (and potential transformer damage).
    High V caps may leak or explode (since they're now getting reverse voltage).
     
  20. kbold

    kbold Tele-Afflicted Silver Supporter

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    There's no red-plating going on (as far as I can see). The red glow you see are the heaters.
    With red-plating, the metal plates will glow cherry red or brighter.
     
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