Tube issues, 12at7 affect KT88?

Hifigeek, looking at it from the side, back row is 4 KT88's.

Front row is 2 12AX, 2 12AT, 1 12AX, 2 12AT. I remember reading the first 12AX is only needed when run in stereo and not mono blocked. So I am assuming 2nd 12AX and 2 12 AT for first 2 KT's, 3rd 12AX and 3rd and 4th 12AT for last 2 KT's. But that's just a guess. It is the 2nd KT that gets hotter, which makes me think it's one of the first 2 12AT, probably the 2nd if my guess is correct.

Heyrazz, what is a DMM? Eyeballing the tubes, it appears everything looks connected.

Continued thanks,

Tony

DMM stands for Digital Multi Meter. Before the display's on the meters went digital, they were called VOMs (volt ohm meters).
They are relatively inexpensive starting around $12.95 at Sears on sale. They measure volage, current, resistance and continuity.
What I was getting at by suggesting you test yout suspect tube with a DMM would be similar to testing a light bulb, the filament is either connected (some resistance), open (no continuity) or shorted ( no resistance). Other uses include setting an amp's bias and testing batteries.

Got it, one of those I have.

Check it out as I described. I'm interested to see if that caused your tube to run away. Someone recently gave me a dilapidated Dynaco ST70 that worked, though not well. The glass on the power tubes were separated from their bases but still functioned as the vacuum was maintained. Basically the tubes were held on by their wires. I replaced the power tubes and as soon as I powered the unit up, one tube glowed bright red and it's cathode biasing resistor blew out, actually splitting in half, thankfully protecting the output transformer. I haven't had the time to figure out what happened yet, whether it was a short, an open, a lousy tube socket or whatever. In fact, I plan on simply overhauling the amp. The power tubes checked out ok and are in another vintage amp. Personally, I suspect a bad socket connection for the affected tube. Reading your situation reminded me of mine. Good luck

Heyraz...Check out the coupling caps in the ST-70. They do go bad. Also if it's really old and the bias supply uses the selenium rectifier, replace it. Those rectifiers leak voltage and the bias supply suffers. Caps in all power supplies as well..