Sound City 40c Mark 6....dead?

[dperry]

Heelo all,

I borrowed this amp from a friend to do some recording with, and in exchange she asked me to change the broken channel toggle switch. I did this and it works fine, but in taking it apart, i unwittingly knocked one of the power amp valves (el84) loose, and when i switched it on, it made a horrible sound and i discovered one of the el84s had died. Before i took it apart, everything was fine.

So...i bought a pair of el84s and fitted them in. Now when i switch the amp on, all the tubes (power amp and preamp) light up, but i am getting no sound whatsoever.

I have tried various leads and cabs and whatnot, but nothing works. Would the fact that its not been biased to the new tubes make it not output any sound?

I have also briefly looked inside for any blown fuses, but couldn't spot any..

Can anyone point me into the direction of what might have gone wrong? Am i looking at an expensive repair job?

Thankfully my friend is very understanding

[dperry]

31 views and no suggestions That makes me a sad panda.

But seriously, what would only having 3 power amp tubes connected instead of 4 potentially do to the amp?

Something like a blown output transformer...?

[pontiacpete]

you could check the output transformer with an ohm meter. But i can't imagine that you blew it.
Does the amp require 4 el84s? Throw a new set in and see if it works

[Amp Kat]

Sounds like you may have blown something open like a screen resistor maybe. You should take the amp back down and visually inspect it good and find out what popped because that is the problem. The amp won't be harmed by running 3 tubes and let's not hope there is a problem with the OT. It is usually the last thing to go when trouble happens.