1967 Super Reverb making weird noises

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by jonnytexas, Apr 27, 2016.

  1. jonnytexas

    jonnytexas Supporting Member

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    I have eliminated tubes and speakers. I know how to discharge caps and not kill myself. I have a good tech, but I enjoy fixing my own stuff when I can. Amp worked flawlessly at a gig Sunday. Sounded like this when I fired it up for rehearsal Monday evening. Help!!

     
  2. swiveltung

    swiveltung Member

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    That's Ugly! Pretty hard to say, but how old are the Filter Caps?
     
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  3. pdf64

    pdf64 Member

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    That's nasty - check that the amp's safety ground connection, ie between chassis and house ground, is solid, and death cap removed.
    It reminds me of a bad heater circuit reference to the chassis.
    Do any of the controls affect the noise?
    How about if all tubes are reseated a time or two?
    What about if all pre-amp tubes are removed?
    Then put V6 back in?
    Then put V1 back in? (Only normal channel will work).
     
  4. jonnytexas

    jonnytexas Supporting Member

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    Still has most of the old mallory blue caps. The ones under the doghouse were replaced 3 years ago. It sounds like s&^t!! Luckily I have two more old supers, but this is the one I usually leave parked at rehearsal space.
     
  5. Blanket Jackson

    Blanket Jackson ¿Qué Hiciste? Silver Supporting Member

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    Have you swapped out any of the preamp tubes yet? (EDIT: never mind, I re-read your first sentence)

    Original (49 year old) caps? Wow, yeah, bring it in - might just be that
     
  6. jonnytexas

    jonnytexas Supporting Member

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    I replaced one tube at a time with known good tubes. No change. Knobs don't change it much. Will try your suggestion about removing preamp tubes. I pulled the chassis and found a 22k resistor that looks like it might be fu^%ed. Gonna try replacing that.
     
  7. jonnytexas

    jonnytexas Supporting Member

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    I replaced all tubes one at a time and also ran to a different speaker cabinet, I'm fairly certain it is not a tube or speaker issue.
     
  8. Blanket Jackson

    Blanket Jackson ¿Qué Hiciste? Silver Supporting Member

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    The practice space were we rehearse has a SF Concert that was doing the same thing. My gut said caps, but a good tech would be able to confirm in about 5 minutes. Money / time well spent in this case, I'd say.

    FWIW when I bought my '67 BFSR it needed a full cap job, and that was almost 10 years ago.
     
  9. jonnytexas

    jonnytexas Supporting Member

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    I agree, but I'm a tinkerer and my practice space is also my office, so I have all day to mess with it.
     
  10. Lobotomie

    Lobotomie Member

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    Can you reach the usual volume levels, but with the added hiss and hum? Or did you get a big drop in volume as well?

    I had something similar, with a big loss in volume. It was a bad filter cap.
     
  11. jonnytexas

    jonnytexas Supporting Member

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    Volume seems normal.
     
  12. jonnytexas

    jonnytexas Supporting Member

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  13. zenas

    zenas Member

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    Check the reverb cables. If they aren't grounded the shield picks up hum like crazy.

    The blue Ajax coupling caps on the board seldom go bad. Those aren't electrolytics.
    Electrolytics do go bad.

    Worked on Sunday now doesn't. Sounds like it might be picking up hum in this space.
    Check the reverb cables.
    Does it do it with nothing plugged in the front?
    Shut the lights off.
    Is it near a computer?
    Hell drag it into another room.

    Anyway check the easy stuff first. I bet it's something easy. Just looking at something inside and replacing it because it looks effed up isn't always a good idea.
     
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  14. jonnytexas

    jonnytexas Supporting Member

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    Wasnt the resistor. Put the old one back. Does it with or without reverb cables. Tech time. I can't figure it out.
     
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  15. Lobotomie

    Lobotomie Member

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    Please report back, I'm curious to know the issue.

    Good luck! :aok
     
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  16. jonnytexas

    jonnytexas Supporting Member

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    10 4
     
  17. pdf64

    pdf64 Member

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    Suggest you check the resistance between either heater green wire and chassis 0V.
     
  18. Jerry

    Jerry Supporting Member

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    Did the hum stop at any time when you removed tubes, or did you put in standby and swap tubes? If so, I would pull one tube at a time, starting with the first preamp tube, until it quits. Pull the power tubes too. If it still hums then....
     
  19. jonnytexas

    jonnytexas Supporting Member

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    Hummed with the removal of every tube, so I'm guessing some type of power supply issue? At this point it is beyond my limited capabilities.
     
  20. Jerry

    Jerry Supporting Member

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    If I remember correctly, I had this happen with a friends Hot Rod Deluxe/Deville amp around 10 years ago and it was the output transformer that was bad. Here's a link to R.G.Keen's site on some tests for an output transformer.

    http://www.geofex.com/ampdbug/outtrans.htm
     

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