jcm800 2204 50W - blowing tubes

[big_teee]

Yeah, it looks like most are that way. Only the very early ones had the lower voltage PT. I agree about the variac. It would also be nice to find out how long it took for the tubes to "burn up". Was he playing, did they bias the new tubes, etc.. If it took some time I'm wondering if something was damaged in the bias circuit and he lost bias. What kind of voltage range do you get from your bias pot? That seems like an awfully narrow range that he gets (-38 to -46).

The voltage range on mine is more because I have a 50k bias Pot.
I started with the TriodeStore layout, then Modded it from there.
with the 50k pot you can bias EL34s and 6L6s.
I've not tried any 6550s.
http://site.triodestore.com/JCM8002204Stock.pdf
T

[MikeH]

So, I have my test OT in hand and I'm going to clip it in and give'r a go. Tubes in, bias set to maximum 'coldness', limiter in use, variac starting at 50% and bring it up slowly. Anything other precaution I should be considering?

Also constantly reminding myself to discharge the amp before trying to unclip the OT... yeah... gotta remember that...