Peavey CS 800x

[vbrotz62]

I have a peavey cs800x Wind tunnel version.I have channel a out.No fuse blown,but amp power light doesn't go on.Channel B lights up.and works fine.I notice the black relay clicks on the b side,but not the A. I'm hoping its something minor.Anyone have this problem before?

[vbrotz62]

After reading most of the related threads I swapped out the drive boards.Good news channel a works with the B board,but not a board.So It is definatly the drive board.Where do I start?What is the most likly suspect,and how do I test it?I have a good multimeter,but no scope.

[Enzo]

You call PV customer service and get the schematics, so we can all refer to part numbers and locations.

You look at your driver card from the back end first. Look at any power supply parts first - like an auxilliary 15v Vreg for example.

[vbrotz62]

I do have all the schematics already.It has to be something on the one driver board.When they are swapped evrything works on either side as long as I swap the good board.I GET NO POWER LIGHT ON THE SIDE WITH THE BAD BOARD.

[Enzo]

Yes, I saw that the problem travelled with the board. I am trying to lead you to the solution.

Look at the schematic section for the driver board. Look along the bottom edge of that circuit near the center. Do you see Q133, the 7815 voltage regulator? That is the Vreg I referred to in my previous post. Does it put out +15VDC on pin 3? If not, is it getting about +26VDC on pin 1? The +26v comes in through pin 5 of the connetor to the output boards, a damaged trace or connector could kill the +26. A bad regulator could kill the +15. And of course so could a dead short IC.

Inspect all the little ICs closely - any cracked ones or signs of heat under them? I only see about 4 of them.

U103 drives the power light, and it needs both +/-15VDC. Since you get no function at all, I suspect it is more than simple LED driver failure. SO check out the -15v supply as well. The -15v derives from the -75v rail. -75 comes on the driver board through pin 11 of the connector, and is dropped through two 1k 5w resistors, R188, R198. Is either one open? Is -75 even getting to them? Q129, Q130 nearby help the -15v track the +15v. SO check them as well.

yes, your problem could be elsewhere, but verifying good power supplies is the first step. You may find that one bad 7815 is the whole problem.

[vbrotz62]

I was doing some research,and I did test the regulator.I believe its my problem.I'm going to see if I can find one locallyand replace it.I will test all you have listed as well.Thanks for taking the time to reply,much appreciated.