Quote Originally Posted by Ali Tait View Post
ECC88 and ECC82 are not interchangeable. Change it for an 82 or equivalent.82 runs a plate voltage of up to 300v,the 88 only to 130v or so. No wonder it's running hot. Take it out pronto! They are not pin compatible either.
As if by magic the shop keeper appears I knew someone would be along that knows what they are talking about

It's a pity a good friend of mine doesn't listen as he'll soon be facing a huge repair bill His KSA250 is running miles too hot & suffering from thermal runaway. I'd expect thermal stability inside of a few hours, this one just kept getting hotter & just before i left there was no way you could keep your hands on the heatsinks for more than a second.. Must have been 60C+ so the transistors must be getting on for 80C+ or more

It's soon going to go bye bye. I did bring this up but all i got in response was "it's a Krell, it's what they do"... I rest my case