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HELP: What could cause...

Discussion in 'Amp Tech Center' started by xjazzy, Nov 25, 2017.

  1. xjazzy

    xjazzy Friend of Leo's

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    ...the reverb on my DRRi bleeding to the Normal channel?
    The only mod I've done was clipping the bright cap and I had to change the reverb tank to a MOD cause the original broke. I'm pretty sure the problem was there even with the original reverb tank.
    I know something is up with the amp cause it's not sonding good when cranked but I want to understand if the reverb bleeding may be related to it.
    It has about 10 years and I've changed speakers and tubes a couple of times.
    I just checked the BIAS and it was too hot (32mA!). I'm using JJs and have it around 21mA now.
    Thanks.
     
  2. Wally

    Wally Telefied Ad Free Member

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    How does this ‘bleeding’ of the reverb make itself known? If one is pushing the Normal channel to some volume and the reverb circuitmis active in the Vibrato channel, there will normally be some reverb due to the shaking of the springs by the vibrations in the amp. If that bothers you, turn the reverb off.
    If however the reverb is actually active in the Normal channel, that is another situation....but you can turn the reverb circuit off, correct?
     
  3. sonicsmitty

    sonicsmitty Tele-Holic

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    I was thinking of starting a thread myself, but since you have one started, xjazzy, I thought maybe I could ask my question here, though I do not wish to hijack your thread and would urge those members with helpful information to help xjazzy first.

    I too have a DRRI, and I find it very annoying when transporting it in the back seat of my vehicle that I can hear the reverb springs slapping the tank housing as I drive, especially since I already have had to re-solder one of those infernal hair-sized wires (what the heck are they, 28 - 30 awg??!!!). I seem to remember that a friend back in the '70s had an Ampeg V4 which had a mechanical "lock" or "damper" for transporting it. If they are effective why are they seldom seen? Is there an easy way to dampen the springs for transport? Is there a substitute tank with a spring damper compatible with a DRRI?
     
  4. clintj

    clintj Friend of Leo's

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    Sound issues + some reverb on both channels may be the cathode bypass cap shared by V1b and V2b going south on you. That'll cause the reverb bleed, one channel getting slightly weak, and the other channel getting much weaker.
     
  5. xjazzy

    xjazzy Friend of Leo's

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    Thanks.
    How do I check if that's the cause?
     
  6. clintj

    clintj Friend of Leo's

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    Well, the right way is to test the existing cap, or simply swap a new one in. On a Reissue, you need some experience with PCB soldering plus knowledge of how to safely work on a tube amp so you don't accidentally hurt yourself or worse. It's easy to overheat a board and damage it, causing a lot more issues.

    There's a few other things it could be, but that combo of symptoms really hints at that cap.

    How old is your amp? If it's less than 2 years old (or possibly 5, depending on when it was bought), it's likely still under warranty. If it's approaching the 10-15 year point, it's coming due for service anyway.
     
  7. xjazzy

    xjazzy Friend of Leo's

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    Almost 10 years.
    I've soldered on PCB before and I know how to avoid getting killed!
    I just don't know how to find that cap...
     
  8. clintj

    clintj Friend of Leo's

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    On the schematic and layout, it's C11. It's near V1 on the main board.

    What you can do is use alligator clips to attach a new cap, in parallel with the existing one, matching up the polarity. That's a 22uf/25V electrolytic capacitor. If clipping that new cap in fixes the issue, remove and replace the old cap and you should be done.
     
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