Ampeg SVT pro3 gone sick on me

[Vernon Fields]

I have 2 SVT pro3 My main amp for Years Just started losing
power and gets destored on 7 fret on my a string. We change the tubes, Took the preamp out my other one, and still no change. It has to be the power board ($300 from ampeg) Any ideas or where to look. I took to a ampeg repair guy who is very good he check with a scop it all show good.
But it still don't work right. I hate to buy a new board when it might be some thing small.

 

[whoatherechunk]

maybe it's time to move on....

 

[DeluxeRed]

On the 3Pro, you can take out post-pre and inject into the power amp, so have you tried either of those? Run the pre into a different power amp and see if it has the same problem? Send a signal direct to the power amp? That might help you diagnose the problem.

 

[Vernon Fields]

Yes I did all that that's how I know it is the power amp board I checked all the caps it got to be a resistor I was just hoping someone might of fixed one with this problem. thanks

 

[Jerrold Tiers]

A good tech should be able to fix it without replacing boards....... First demo the problem, and that should get him on the track.

They are very simple. if the tubes have enough voltage, and the bias is good, they oughtta work. Any serious problem would blow a fuse, cause smoke, no output, etc, etc..

There are some auxiliary power supplies for the mosfet bias that could be bad.... typically that sort of thing is a bad solder joint, as with the "losing power" thread recently... that was one broken solder joint.

 

[Vernon Fields]

I'll give that a try I took it a Authorize ampeg repair guy in Town he wants to put a new board in it. I could do that I'll try checking the solder joints.
Thanks