JayCartay
Registered User
Join date: Apr 2012
1,991 IQ
#1
Dear god. I made a thread a few days ago about having put new JJ 6L6GC tubes in my Peavey Classic VT100 and hearing a bit of a weird hum for a few seconds when powering on.

I thought it was resolved and last night played through the amp for over an hour. Tonight I've fired it up, played a few notes to get in tune then taken the guitar cable out to plug it into my M-Audio interface. I left the amp on and after a few minutes noticed a burning smell. I then realised the amp was making a constant hum that was getting louder.....

Looked at the back and one of the new tubes was lit up like a christmas tree!! Not just the bit that's meant to light up, no, the WHOLE thing!

Wtf do I do now? Woukd this simply be a faulty tube, seeing as I had no problems on the old tubes?
KG6_Steven
Eats ponies for breakfast
Join date: Nov 2006
3,132 IQ
#2
A tube that has red or orange plates is a bad thing. Turn off the amp. Most likely that tube is bad. Replace and all should be well. If you keep the amp turned on, it will result in a larger repair bill.
JayCartay
Registered User
Join date: Apr 2012
1,991 IQ
#3
I turned it off as soon as I saw it. I'll contact the guy I got the tubes from.
bobt68021
Registered User
Join date: Nov 2007
348 IQ
#4
I was one hundred percent sure you just came up with an awesome name for a song about hard drugs and made a thread to tell people. But damn that does suck tho and I know nothing about tube amps sorry.
R45VT
Doesn't speak guitar
Join date: Dec 2009
1,110 IQ
#6
Tube red plated, no good.

Were these tubes new?

Sometimes when a tube takes a dump if left on long enough it can hurt some of the resistors inside the amp. Just be aware when you put new ones in. If anymore problems pop up it would need to be inspected by a tech.
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JayCartay
Registered User
Join date: Apr 2012
1,991 IQ
#7
I'd say it had been on maybe ten mins so who knows. I will get new tubes and see what happens. Infact, I may plug the old ones back in before I put brand new ones in again to make sure the same doesn't happen.
R45VT
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Join date: Dec 2009
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#8
Quote by JayCartay
I'd say it had been on maybe ten mins so who knows. I will get new tubes and see what happens. Infact, I may plug the old ones back in before I put brand new ones in again to make sure the same doesn't happen.


That is the best route.
Quote by DeathByDestroyr
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AcousticMirror
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Join date: Dec 2009
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#9
your bias on the new tubes is off.
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JayCartay
Registered User
Join date: Apr 2012
1,991 IQ
#10
You're meant to be able to plug and play on this amp.

Absolutely no issues whatsoever on the old tubes tonight.
AcousticMirror
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Join date: Dec 2009
4,843 IQ
#11
oh you're meant to be able to plug in play?

there's no possible reason it shouldn't work then.

have fun.
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Eppicurt
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#12
Quote by AcousticMirror
oh you're meant to be able to plug in play?

there's no possible reason it shouldn't work then.

have fun.

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ne14t
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Join date: Mar 2011
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#13
Quote by JayCartay
You're meant to be able to plug and play on this amp.

Absolutely no issues whatsoever on the old tubes tonight.


Is it a self-biasing amp? I mean they do exist but from what I know the older Peavey's did not have this circuitry, and biasing really makes a difference I couldn't figure out what was wrong with one of my amps when I bought it (Haze 15), well it came from the factory roughly 50% cold, re-biased it and it was a whole new beast. Also tubes all have internal resistances that very from tube to tube so if you put all your old tube back in which the amp is biased for of course it will run properly. Then again it could have been a bad tube as well JJ's are Chinese made tubes and tend to have a higher failure rate, but also have the highest gain so it is a trade off, not knocking JJ's it's just the truth, my Haze 15 runs JJ's in the preamp and they haven't been touched in almost 2 years.
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R45VT
Doesn't speak guitar
Join date: Dec 2009
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#14
Quote by ne14t
Is it a self-biasing amp? I mean they do exist but from what I know the older Peavey's did not have this circuitry, and biasing really makes a difference I couldn't figure out what was wrong with one of my amps when I bought it (Haze 15), well it came from the factory roughly 50% cold, re-biased it and it was a whole new beast. Also tubes all have internal resistances that very from tube to tube so if you put all your old tube back in which the amp is biased for of course it will run properly. Then again it could have been a bad tube as well JJ's are Chinese made tubes and tend to have a higher failure rate, but also have the highest gain so it is a trade off, not knocking JJ's it's just the truth, my Haze 15 runs JJ's in the preamp and they haven't been touched in almost 2 years.


JJs made in China?

Stop posting bullshit.

Made on old Tesla equipment in Eastern Europe.
Quote by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.
JayCartay
Registered User
Join date: Apr 2012
1,991 IQ
#15
Quote by AcousticMirror
oh you're meant to be able to plug in play?

there's no possible reason it shouldn't work then.

have fun.


No need for the sarcasm. I've been reading up on this almost constantly since the failure. Many, many people have stated that although the amp is fixed bias, and ideally should still be adjusted, in most cases you can plug and play with new tubes because of the way the tolerances are set.

I'm not saying I'm 100% right, I'm just relaying what many other owners have stated. What else can I do??
Cathbard
Grumpy Old Tech
Join date: Oct 2009
2,565 IQ
#16
I think Min is saying that there is a fault in the bias circuitry that is causing it to be out of bias, and he could very well be right.
Put your old tubes in like you said you were going to and watch closely what happens. Stay near the power switch so you can kill it fast if they start to redplate too. Keep the lights dim so you'll see it earlier. If that happens the amp has a fault - and it will probably be in the bias circuitry, just like Min said.
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Wesbanez
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#17
Quote by JayCartay
What else can I do??


Er, you could accept that no matter what the manufacturer and/or random noobs on the Internet tell you, you should learn to bias your tubes or get a tech to do it.

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JayCartay
Registered User
Join date: Apr 2012
1,991 IQ
#18
Nah I played it for a good half hour last night on the old tubes, and kept going to the back of the amp every few mins or so to check on it. No redplating at all. Everything worked perfectly.
JayCartay
Registered User
Join date: Apr 2012
1,991 IQ
#19
Quote by Wesbanez
Er, you could accept that no matter what the manufacturer and/or random noobs on the Internet tell you, you should learn to bias your tubes or get a tech to do it.



Aye possibly so. Just need to be 100% sure before going to the trouble of finding one and having it done. The next set of JJ's that are going in are colder than the first set. Will that make a difference or should I still have someone look at it?

The next question then, would be: if I do let someone look at it, should I go ahead and ask them to do the Bias pot mod and replace the 68k resistor with a 50k bias pot and an 18k resistor?