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Tube issues, 12at7 affect KT88?

Hello. I have a McIntosh 275V. I just tube rolled my 12AT7's. Started listening, and one of my power tubes, a Penta Labs KT88 went bright cherry red. I shut it down quick, let it cool down and swapped back. Looks like it's back to normal. Letting it cool down again and I'll swap tubes again and see what happens.

If it goes cherry again, what would make the 12at7 affect the power tube like that?

Thanks in advance,

Tony
tonydec
griffithds
852 posts
 
Did you test the 12at7's for shorts before inserting them into your system?
tonydec OP
23 posts
 
No I did not. I will be getting them tested. I swapped them out, seems to work fine. Put them back in, same thing, one power tube started getting very hot. It's obviously something in the 12AT's. I think I have it down to a couple of them, as I placed them back in the same order with the same results, but I'll get them all tested.

I'm not very well versed in tubes, but that was my guess, a short. It made music with no weird noises, just ran that one tube very hot. Good thing I was watching closely as they were new to me tubes, and it appears I shut it down before any damage, other than maybe shortening the life on that one tube?

Tony
heyraz
177 posts
 
Was the power tube's socket "stretched out" and not making good contact with all of the tube's pins? That's the first thing I would have checked. You should rule out the simple stuff first.
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