Peavey CS 800 Blows fuse

[arambharose]

Oh I sorry. What I meant was when I input a signal into both channels at the same time,sound comes out of channel A speaker terminal only.

[Jazz P Bass]

Can we please identify "which" board is bad.
I have attached the board layout diagram.
It would go a long way to repairing this amp if we could all be on the same page, so to speak.
Use the "names" of the boards as indicated in the layout.
You know Channel A works.
Swap Channel B boards into A until you can identify which board is bad.
Then we repair that board.
Simple, huh?

[Enzo]

I don't recall what we had determined. WIth siignal at the input jacks, on the "bad" input board (the board with the volume control), is the signal at the hot leg of the volume control? Hot meaning the leg farthest from the grounded end. The hot end connects to C4. If signal is there, is it also on the wiper leg - the center of the three pot legs? Have the control turned up for this.

In one corner of the input board, there are two side by side 3-pin molex connectors. Right next to them is an 8-leg IC, U1, a type 87478. Remove it. Does the amp channel work now?



Basically, if this little board won;t pass signal, there is not much there. SO get rid of the DDT chip, U1, then apply signal to the input, then trace it from the jack to the molex connector to C5/R20, to C4, then to the volume pot. Then from the volume pot wiper, through R17, to the other Molex where it leaves the board.

[arambharose]

I narrowed it down to input board of CH B

[Enzo]

Good. Try what I suggested,remove the 478 IC. ANy help? If not then trace signal through the path.