bigblock 750 / dead preamp tubes ?

[guiguite]

hi everyone

I got a small trouble with my bigblock that will hopefully be easily fixed but i wanted you opinion about it.

Last time i tried to play it , it went all fine for like 20 minutes and after that i didn t had any volume at all but a weird hum, a bit like the noise between two radio stations.

I checked all the cables, the bass and bladibla, it s all fine.

If i put the amp really loud (like 75 % gain and volume) i heard a tiny distorded bit of bass behind the hum and that s all.

Is this thing typical of dead preamp tubes? Like when they are cool it s fine but when they warm up, something happen.

i hope this is it... otherwise, what could it be ?

i opened the amp and checked the valves, they are still lighting up but they are not doing the "ringing" thing when i hit them gently with a pen...

i tried again today, and it does the same... 15 minutes and then humming

thx in advance.
gui

Edited August 10, 2008 by guiguite

[The Burpster]

Certainly sounds like a tube has let go.

[guiguite]

thx, i hope it s that... can t really affort to pay for a repair right now :wacko: