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Redplating tube = Tech time?

Discussion in 'Glowing Bottle Tube Amp Forum' started by WilburBufferson, Jun 8, 2017.

  1. WilburBufferson

    WilburBufferson Friend of Leo's

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    I recently bought a used Rivera Clubster 25. Played it at low volume around the house for about a week without issue. Tonight I was able to crank her up at rehearsal. With the clean channel at around 7 on the volume there was a pretty sudden volume drop, and then the tone became distorted. I looked at the tubes after about a minute and one was redplating. I powered down the amp immediately.

    Could it just be a bad power tube, or should I have it looked at professionally? As I understand things from a little bit of research, read plating is always a sign that something is terribly wrong. Right?

    Here is a picture of the tubes. The one on the left is the one that was glowing.

    IMG_9824.JPG
     
  2. WilburBufferson

    WilburBufferson Friend of Leo's

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    Was also wondering if the above tubes were matched? The number on the left side are, but the initials are not. What do they mean/stand for?
     
  3. robrob

    robrob Poster Extraordinaire Ad Free Member

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    There's your problem. Those tubes are not matched. One has a grey label and one a red. I'm surprised the amp didn't explode.

    But seriously, a dying tube can red plate. I would replace the tube that red plated and then play the amp in a darkened room to better see if the red plating comes back. If it's good after a few minutes of wringing out the amp I'd chock it up to a bad tube. If it does return then it's tech time.
     
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  4. peteb

    peteb Friend of Leo's

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    The lettering on the left tube could be the groove tube paint that changes color when the tube gets old.

    They both have a 4 on them under where it says performance.
     
  5. WilburBufferson

    WilburBufferson Friend of Leo's

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    I thought the same thing about the grey versus red paint on the tube. Both are "4" but the other 3-character code is different, so I wondered if they were matched. I emailed the previous owner. He said the tubes were changed 5 years ago, but after the same tube (on the left side too, he thinks) burnt out. He is a bedroom player, so I can't see him turning the amp up past 2. Last night I had it at around 7 which is when things started crapping out. Am I correct in saying that more current flows to the power tubes the higher the volume? In other words, if the problem is elsewhere in the amp (and not the tube) then it wouldn't become apparent until you turn the volume way up.
     
  6. PCollen

    PCollen Friend of Leo's

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    That tube on the left is likely bad. I'd suggest a new set of 6V6's ..replace both with a matched set. But first, you could also swap the two tubes and see if the other one red-plates in that socket where the previous one was, which would point to a problem in the circuitry surrounding the power tubes, or the bias voltage to that socket, or several other things that a good tech could identify and resolve.
     
  7. dsutton24

    dsutton24 Doctor of Teleocity Ad Free Member

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    I'm not sure if some of the joking abound is obvious, so forgive me if I'm being dense...

    As Rob says, a bad tube can red plate. It's probably worth replacing the tube and watching it closely in a darkened room. If it starts glowing red, shut the amp down immediately and get it into the hands of a good technician. I don't know anything specifically about the amp in question.

    Red plating is almost always a bias problem. It could be something as simple as a bad contact to the tube screen, it could be failed components. I wouldn't expect that running it at high volume was a direct cause of the problem, tube amps are meant to be played loud. But, keeping the volume down may have masked a problem caused by a failing component.

    The different color of the one on the left means it has been overheated. I've got a pair just like it in my junk box :) Red plating is always bad, that tube is toast. If it was my amp, I'd replace the pair.
     
  8. WilburBufferson

    WilburBufferson Friend of Leo's

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    That's what I was getting at. I think I'll take it in, just to be safe. Around here (in Toronto), there's nowhere good to buy tubes. There's a store an hour away that has a wide selection, but before committing to that, I think it would be prudent to have a pro check for said failed components.

    Before the tube failure, I was digging the tones. It's a manageable amp to carry and plenty loud. What a headache though. This is the third tube-related issue I've had to deal with in the past month. It's getting me to start re-thinking about picking up a Mustang III.
     
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  9. Commodore 64

    Commodore 64 Friend of Leo's

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    If the power tubes are 5 years old, then really, you have nothing to complain about. That's a fixed bias amp, so in principle, you need to check the bias and adjust as necessary.

    In practice; however, the majority of people do something like the following:

    1. Buy a pair of EH 6V6GT or JJ 6V6GT . Matched. These are 14 watt tubes and your amp certainly wasn't originally biased with anything higher than 14W reference.
    2. Play it in a dark room. If no redplating occurs, and the sound is good...you are all set.
    3. If not, then it's tech time.

    Pretty sure these are Canadians: http://www.thetubestore.com/

    http://www.thetubestore.com/Tubes/Electro-Harmonix/Electro-Harmonix-6V6GT

    That's 21.95 for a pair of matched 6V6GT. Bought from them many times.
     
  10. Zipslack

    Zipslack Tele-Meister

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    You will need to replace the tubes with a matched pair. The color on the logo indicates the tube got excessively hot.

    Since the previous owner indicated the issue has happened before, I would say it's tech-time. Specifically, I would:
    1. Clean and re-tension the tube sockets
    2. Re-flow solder joints on the sockets...most likely issue in my experience
    3. Check voltages and adjust bias (assuming this amp has adj bias).
     
  11. jtcnj

    jtcnj Tele-Holic

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    I have purchased matched pairs of JJ6v6gt and JJel84 here:
    https://www.tubedepot.com/products/jj-6v6s-power-vacuum-tube

    select matched pair; there is no upcharge.
    Shipping to me in NJ is about $6.00.

    I have been meaning to check how closely they are matched but since both amps they are in are cathode biased I have had no urgency to do so.
     
    Last edited: Jun 9, 2017
  12. KB11

    KB11 TDPRI Member

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  13. codamedia

    codamedia Poster Extraordinaire

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    ^^^ This ^^^ is what I would try while waiting for the new tubes to arrive.
    • If the "red plating" follows the tube... it's likely just the tube.
    • If it stays on the socket and the other tube now red plates - it's a sign the circuit needs work. I wouldn't put new tubes in until this problem is corrected.
    That is not a definitive test... but if can give you an idea of where the problem is.
     
  14. WilburBufferson

    WilburBufferson Friend of Leo's

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    Thanks folks. I'll try a tube swap and let you know what happens.

    Not sure how Commodore 64 got $22 for a matched set. Maybe that per tube...!
     
  15. PCollen

    PCollen Friend of Leo's

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    Is the Mustang III still being sold ?

    I bought a Mustang III in January and really enjoy it. I also have a Fender Blues Jr., and an Epiphone Valve Jr. Head and a Marshall JTM50 clone head both of which I plug into a 2 x 12 cab. Since getting the Mustang III, I've ignored my tube amps .
     
  16. WilburBufferson

    WilburBufferson Friend of Leo's

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    So last night, in a dark room, I switched the existing power tubes and powered the amp up. I let it run for about 10 minutes. I couldn't play through it because it was too late at night. Neither tube was red plating but the one that previously overheated was glowing blue. I'm not sure this tells me anything new.
     
  17. codamedia

    codamedia Poster Extraordinaire

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    Try again today and turn it up just a little keeping a close look.

    The blue glow really doesn't mean anything... but if neither tube is red plating then the "circuit" is likely fine (key word is likely). The tube that redplated is likely on it's last legs (if it isn't dead already), but the other one can be used for a "spare" in a pinch.

    Really? That would surprise me. You have some great music stores in that city... surely someone has a good stock of tubes. Even our local L&M in Winnipeg stocks a large selection and variety. Where they fall short, the other stores are happy to fill the gaps.

    I assume this is the "Tube Store" down in Hamilton which is the equivalent of "Tube Depot" in the US. I've bought a few things from them... it's a good outlet.
     
    Last edited: Jun 10, 2017
  18. WilburBufferson

    WilburBufferson Friend of Leo's

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    So with an empty house yesterday, I turned the volume up AND had my guitar connected. This was the result. The tube on the right was previously on the left side, red plating. So the problem is following the tube. I'll see what the turnaround is for the tech though. Can't hurt to have a checkup.

    Regarding other points: you would think that L&M would have a decent tube selection, but in my experience I have found the selection and advice to be hit and miss. For example, they do not carry JJs which I understand to be suitable, for this amp, as they can handle higher voltages.

    Yes, the store I was thinking about is thetubestore in Hamilton. A matched pair of JJs from them (with tax and shipping) is about $55 USD which is why I am inclined to take it to a tech -- I don't want to burn up a brand new set at that price.
     
  19. WilburBufferson

    WilburBufferson Friend of Leo's

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    IMG_9830.JPG
     
  20. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Since the problem is following the tube the tube is the problem. You should be safe to install a new set of tubes and be on your way.
     
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