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Weird grounding issue

Discussion in 'Amp Central Station' started by Telegator, Apr 6, 2014.

  1. Telegator

    Telegator Tele-Afflicted

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    I hope this isn't a question that has been beaten to death before but this issue is of a first time nature to me. I would appreciate any help in troubleshooting this.

    I have an '85 Peavey Bandit 65 Solo Series. Over the last couple of days it has started making a noise that sounds like a guitar cord is plugged in and is being touched by your hand. It starts low and gets loud but the amp continues to output the guitar signal. A flip of the three way ground switch stops the noise instantly until sometime later it again starts making the noise. Flipping the three way ground switch back to its original position agains stops the noise. This goes back and forth at about 3-5 minute intervals.

    The amp seldom leaves the house. The last time I used it away from home was October 2013. The only incident I can tie to the issue is that I unplugged a Digitech RP155 a couple days prior to this staring.

    Any ideas on what is wrong with this old Bandit? It's been a good amp for a long time and I hate to replace it but if it would be more cost effecient to replace it with another Bandit it will be what I go with. Still, I'd like to save it.

    Thanks in advance for any and all help!
     
  2. backline

    backline Tele-Afflicted

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    I am not familiar with those amps, but.....3 way ground switch.?
    Does that amp have a 3 wire power cord.? .....and also some type of "ground" switch.?
     
  3. Telegator

    Telegator Tele-Afflicted

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    There is a rocker switch on the front of the amp with three positions. "+" at top "-" at bottom with the center position unmarked. It is located beside the power switch
     
  4. Johnny Cache

    Johnny Cache Former Member

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    Whats it do in the middle position?
     
  5. backline

    backline Tele-Afflicted

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    You should ask one of the techs...I would think in 2014 that you should abandon all that crap.
    He probably has a cap across the PT Primary...grounded on the Neutral side...and then a (separate) switchable cap to ground that can reference the Hot...Neutral, or Nether.
    Any one of those two caps can be causing you problems.
    I assume it is a throwback to earlier days...and Peavey held onto the transition "technology".
    I say open it up, and just wire it like any other 3 wire power cord...ditch those two caps.
    But ask somebody like Wally for his advice first.!
    Good Luck
     
  6. Wally

    Wally Telefied Ad Free Member

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    Since I have been mentioned.....then I am curious. How old is this Peavey? I ask because these solid state amps have electrolytics in them also, and those go bad in SS circuits just the way they go bad in tube circuits. E-caps can cause situations like this....coming and going of noises..I would think this is a hum, right? The 'polarity changes may re-establish the flow of electrons and filtering monmentarily, but then the caps 'goes bad' again. This is not an unqualified firm diagnosis for this particular amp, but if it is an old amp, imho, the electrolytics need to be changed.
    Re: that polarity switch...yes, the death cap thing. Most of us like to remove it. Some rare few like to maintain that polarity flexability. Most of those players are using the amps in recording studios a lot.
    IF this problem is a weak e-cap, get ready for the amp to stop making any sounds at all. No matter what the problem, it is time for a tech to look at the amp. Also, buying another BAndit might not be a 'fix' for this...because it might be as old or older than the one that the OP has that is giving this problem.
    My fix for the situation would be to buy a tube amp...but then those of you you know me expected that, right?!? LOL
     
  7. Telegator

    Telegator Tele-Afflicted

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    Wally, thanks for your advice. You asked if the noise was like a hum. The answer is yes. Your diagnosis sounds right but it is more info than I understand :lol:

    This is an old 1985 model but parting it out or storing it seems sad to me. Your advice to haul it to the shop is certainly my best bet. Even if I buy a new one I want to get this one fixed.
     
  8. steveneddy

    steveneddy Tele-Meister

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    Yeah - if this is over your head take it to an amp shop with a good reputation.

    Get it repaired and maybe get some preventative maintenance done while it's in there.

    Then go purchase a good little tube powered amp.

    IMHO you will be much happier.
     
  9. Telegator

    Telegator Tele-Afflicted

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    I believe my issue is resolved. I talked to a guy who worked on Peavey amps years ago and he made me do a simple test. While the amp is powered up flip the switch back and forth several times. I did and in all three positions it would make a noise as I worked the switch. I then stuck a piece of tape on the switch to sort of "splint" it still. No issues after that.

    He told me it is likely just the switch itself and that it is a simple fix. I'll bring it to him in a few days but for now I can at least play it. Thanks to all for your help and advice.
     
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