JTM45 volume fading

[Birk]

Last night I was playing with my JTM45 RI through a THD Hotplate and a 1922 cab. I used both channels (both volumes at 7) with a A/B/Y pedal, rockin' out, then I hit the booster (catalinbread chilli picoso) and the volume startet wobbling and fading.

What happened? What did I do wrong?

Let me mention that I've just swaped 6L6's for KT-66, are they biased to hot?
All tubes are new JJ/TAD.

Help me please!

 

[Brett Blackmore]

It could be anything from your pedal to a bad component in the amp - but you are right, most likely the main tubes are not biased right. I would have these checked out again.

Also it could also be the output transformer is failing to cope with the power soak or the cabling - once you check out the tubes also check out the amp again without the powersoak. Check the sockets and speaker cables.

Good luck!

Brett

 

[jcmjmp]

JJ or TAD KT66? You should have gone with Gold Lion KT66, but that's another story.

Maybe your new tubes are bad. Try swapping the preamp tubes and see if the problem still happens and have the tube sockets cleaned/re-tensioned. Don't go doing this on your own because re-tensioning them could shock you.

 

[Birk]

Thanx for your reply, I will check bias again.

When I turned the booster off, the sound returned back to normal. I didn't dear test for more than a few seconds as I was afraid to damage the amp.

Come to think of it, could the volumefading have something to do with that I was running both channels at the same time? Or should this amp tolerate this?

The KT-66 are JJ's, TAD preamp tubes.