Marshall 9005 Low output

[wnlively]

HI
I purcased a Marshall 9005 power amp on ebay.
I really never used the amp and after a few months decided I would try it out.

I found that the amp only has about half the output on one of the channels as the other.
I have replaced the pre amp tubes
replaced and rebiased the output tubes.
Both side of the amp are putting out 460 volts

Can any one give me any ideas on where to start looking next ?
A schematic can be found at http://www.diyguitarist.com/Schemati...5Schematic.gif

thanks
Neal

[Alton]

Neal,

There are no preamp tubes in the Marshall 9005. Those 12ax7 tubes in the 9005 are phase inverters.

Which preamp are you using?
Is it a stereo preamp?
Did you clean the input jacks into the 9005?
Did you clean the output and FX loop jacks in your preamp?
Are the cables from your preamp to your 9005 the same length and same gauge?
Try the cable from the preamp to the good side of your 9005 in the weak side of your 9005. This should eliminate any of the simple problems.
If you still have a weak output then it's probably time for a trip to your amp tech.

[wnlively]

Hi and thanks for the advice
The amp has the problem no matter what pre amp I use and I have tried all of the simple fixes.
What I fear is a costly trip to the shop