What's The Deal With Twin Reverb?

Discussion in 'Amp Tech Center' started by Thirteen, Oct 13, 2014.

  1. Thirteen

    Thirteen TDPRI Member

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    Last spring my TRRI died. One of the power tubes blew and took out some resistors, I had it repaired, new set of 6L6s and biased then it sat around until last week.

    I was getting ready to use it again for the 1st time next weekend and it was giving my nasty crackles/hisses when I strummed or took it off of standby, otherwise no weird noise. I also noticed a faint burning smell coming from the amp.

    It did the same thing with a different guitar and on different channels.

    I played around with the tubes and when I wiggled the far left tube (looking at amp from behind, I think it's the V10??) the same crackle/hiss noise started. I also noticed at this time that the tube had a faint blue glow and it began to glow much brighter than the other 3 tubes, just like it did last year before it was repaired. I swapped tubes around and it glowed bright and hot in the same position with a different tube.

    I kept playing around with it, never leaving the amp on long enough to possibly blow a fuse or (hopefully) melt anything important. Suddenly, the amp made a goddawful, screeching feedbacky noise that I couldn't control so I quickly threw it into standby then complete power off. I'm kind of an idiot so I just had to turn it back on and see what was going on after that. I powered it up several times, played, left it on for several hours and put it through live gig conditions and now it acts like nothings wrong. No smell, noises and all tubes glowing the same. It's almost like I exorcised some demon out of it when it screamed and now everything's fine. I'm kinda wary about using this weekend though.

    Does this make any sense? Do you guys think it's good to go?
     
  2. Wally

    Wally Telefied Ad Free Member

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    Your amp has something wrong with it...might be a loose tube socket??? Bad connection on a tube socket?? Piece of dirt in the socket?? Bad connection on a resistor elsewhere that is affecting biasing???
    You say "I swapped tubes around and it glowed bright and hot in the same position with a different tube." Was that a case of the plates glowing red?? IS so, you have an intermittent problem in the bias circuit to that tube, I would guess. Anytime you see a redplating tube, the amp needs attention. Your exercise of moving tubes around was of value, and the tech needs to know that.
    I would not trust it to be run. One thing.....any smell of electrical 'burning' is a sign that an am p really doesn't need to be turned on except by a tech who is doing so evaluation/investigation.
    I will make this observation. Any time an amp has had work done on it, the owner needs to play through it in a timely manner to assure that the amp has actually been repaired. IT sounds as if what affected the amp last spring may still be lurking in the shadows here....or the failed tube might have taken something out that wasn't addressed. I vote for the first option.
    By not playing it much when you got it back, imho and ime you have done something that can be irksome to techs.....techs don't like to have a job come back after this long of a time with a 'the first time I wanted to use it, it wouldn't work." When I am presented with such a situation, I have no assurance that the amp hasn't been played to death since I last saw it....and there is no guarantee on the work that I did all of those months ago after all of this time has passed.
    My advice....don't turn the amp on. Take it back to the tech...if you trust them. explain what has happened...including that tube swapping/tubes glowing in one socket thing. That bit of knowledge should lead them to the area of the problem.
     
  3. Coop47

    Coop47 Poster Extraordinaire

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    Adding to Wally's post above, I had a similar screeching issue with an SFTR and it turned out one of the power tubes was inserted incorrectly.
     
  4. Thirteen

    Thirteen TDPRI Member

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    Yeah, the tube's plate was glowing bright in that position. I do agree that I shouldn't have waited to try the original repair out. It was one of those things that was always on my mind to do and although it would have been quick and easy, I just never made it a priority. As such, I'd already figured that I owned any problems with the amp even if it was a result of a bad repair job.

    On the bright side, I took the amp to a different, well-regarded music shop/repair guy to see what he could diagnose. To my surprise, he opened it up right there while I waited and poked around. He thinks that the factory installed incorrect value resistors so he soldered in the correct ones. When he tested the installed tubes he thought they were a little overpowered for what I needed. I already had a matched set that I wanted the original guys to re-tube with so he put them in and biased the amp. Essentially, he poked, checked, cleaned and tightened everything while I chatted with him for 30 mins and it only cost me $20 plus I gave him the old, hot tubes since he could use them for something else. I found out why he's so well respected and he earned another loyal customer so I guess it all worked out OK.
     
  5. Wally

    Wally Telefied Ad Free Member

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    Yeah....you got a bargain. Pleease don't forget him...it is a hard world out here working on musical equipment.
     
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