#1
Hey guys, so I'm in a bit of a bind. I'm using my Marshall JCM 2000 TSL 122 amp again, and my tubes are acting up. The amp will run alright for a bit, but then one set of tubes will start glowing REALLY brightly (like, hot enough to start burning the brand print on them) and the other set will glow much less. I rebiased today and I had the same problem, so I'm guessing the hot set has gone bad?

Ideal situation is I just have to buy new tubes, but I'm concerned that there's more of a problem, especially since I'm playing a show Thursday and don't have a way to get the amp to a tech. Any ideas?
NOPE
#2
Might just be a bad tube. Try reinstalling the old set, if possible. Don't let it run like this for long, or you risk popping the fuse... or worse. If it still does it with the old set, then you have another issue that will require a tech.
#3
Sounds like it's biased too hot - if you are talking about the power tubes.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#4
I checked the bias this morning. The "hot" pair was set a little high, and the "cool" set cool, so I set them both to a warmish bias. However, the problem came up again. Is it possible to have a set of tubes go bad like this? Its not just one tube getting really hot, its a pair.
NOPE
#5
It's possible but a bit odd.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#6
I should add as well, its a set of groove tubes, which ive heard can be pretty shoddy so... who knows
NOPE
#7
There are all sorts of Groove Tube tubes. They test and relabel other valves. You have to read the entire code to know what you have got.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#8
Ah yeah, I remember reading about that awhile back. What should I look for to see what I might be getting? I'm planning on hitting guitar center tomorrow to grab replacements.
NOPE
#9
GT-EL34S are JJ EL34, GT-EL34LS are JJ EL34L (a beefier version of the EL34), the S stands for Slovakia
GT-EL34C are Chinese Shuguangs
GT-EL34R are Russian Sovteks.

Of those the S or LS are best, next are the Chinese ones. Stay away from the R's.
M's are the Russian Sovtek Mullard "reissue" (they bought the name, they aren't the steam off a Mullard's turd). They are better than the R's but I wouldn't buy them myself.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#11
Welp, got new tubes today and it was still having problems. Rebiased again and everything. Still a bit of a shot in the dark, but any ideas why one pair of tubes would start burning really hot?
NOPE
#12
You have a fault that will take more to diagnose than a few posts in a forum. Take it to somebody that knows what they are doing.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band