Bad Cat problem

ed_dale007

Member
Messages
210
I was re-tubing my black cat with some new jj el84's popped them in and all of a sudden the amp seemed louder in the half power setting and I could smell burning and looked in the back on of the tubes was significantly brighter than the others. Also there was a loud hiss when in the full power setting. Anybody have any clue what could be going on?
 

teleamp

Senior Member
Messages
3,478
Who did you buy your tubes from? Unfortunately, some vendors don't weed out the bad ones and let the customer be the QC.


If the old ones are still good does the noise go away?
 

GlueMan

Member
Messages
991
There seems to be a pattern. My Black Cat that I had did something similar, although not as extreme, burning one tube MUCH hotter than the others. Also, if you search the Tech forum, someone else had the same trouble no more than 1 or 2 months ago.

I don't recall exactly what the problem was, maybe a resistor going to the power grid?
 

samuelson

Member
Messages
688
buy your tubes from eurotubes. that is a tube problem, not an amp problem. I have three bad cats, changed the tubes, never had a problem. buy my tubes from Eurotubes.
 

Madison

Member
Messages
7,314
I had the same happen with my SC30, redplating. You may want to try putting your old tubes back in and see if the problem goes away, it probably will...if not you'll need an amp tech. The Black Cat is basically the same amp, you'll have to choose your power tubes carefully. If you use a guy like KCA, tell him which amp and he can select power tubes that should be okay.
 

GlueMan

Member
Messages
991
buy your tubes from eurotubes. that is a tube problem, not an amp problem. I have three bad cats, changed the tubes, never had a problem. buy my tubes from Eurotubes.
My similar problem was an amp problem and it took an amp tech to fix it. I changed and rearranged tubes numerous time trying to fix it before sending it to be fixed.
 

ed_dale007

Member
Messages
210
Yeah I'll pop the old tubes back in and give it a try. I got them from the tube store I don't think I'll send them back I already bought some TAD EL84's which wouldnt fit in my black cat (wish I would have known this), and he sent me some JJ's. I really don't feel like going through the entire shipping and waiting process again.
 

Madison

Member
Messages
7,314
The ones I had that were bad were also JJ's. I had to send them all the way back to Canada...a real pain going through customs and all, but they promptly replaced them.
 

ed_dale007

Member
Messages
210
So I replaced the red plating el84 with another JJ seems to have fixed the problem. Anybody know of those russian el84m's fit in early black cat's? I would prefer not to use JJ's next time I have to re-tube.
 

distorted noise

Silver Supporting Member
Messages
689
i just put a pair of JJ's EL84's in my badcat and they work great. i bought a matched pair from Dougs Tubes.
 

micjonga

Member
Messages
201
You know I recently purchased some JJ 12ax7 tubes and found 2 brand new ones to have WAY less output when placed in V1 than other tubes I had. I'm talking a significant drop in volume! I also purchased 1 matching quad and 1 matching pair of JJ el84s and they were fine.

Weird?

Sounds like a QA issue to me!
 






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