Ampeg SVT-4 Pro Troubleshoot 7vdc offset on both A and B outputs.

[Ewbank]

Hi,

I have an Ampeg SVT - 4 Pro that is producing a 7vdc offset on both outputs. This has contributing to it blowing out a cab. Here are the schematics:

428xxh0_.pdf
428XXp9.pdf
53904H0.pdf
53904p1.pdf
76201H0_.pdf

When the master volume is increased the offset increases to a max of 7vdc.

What do people think is the best way to diagnose this problem?

Cheers
Ewbank

[Jazz P Bass]

I would start by checking what is common to both outputs.
The power rails.
+V & -V.
+15 & -15.

[MarkusBass]

I would check also +/-VD (the amp has double high voltage rails) and whether the ground wire from the transformer is connected to the amp. The issue with the pot is strange because the pot is DC separated from the power amp. This would suggest some problems with ground or power supplies. Check what Jazz suggested.

Mark