CS800s Amplifier Power Module Died

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CS800s Amplifier Power Module Died

Post by FreeFallin » Wed Sep 09, 2020 8:49 am

Hi All,

Short Version: The amp died, no signs of life. I found the .160 amp slow blow fuse (F2) blown in the power module. I can replace it, but is that likely the problem, or a symptom of something else?

More details:
I have a Peavey CS800s power amp that I bought new 20 years ago for mobile DJ use, it was used regularly for a few years and then once or twice a year until a few years ago when it died. I love this amp, I have basic experience with electronics and soldering, help me save it.

Turn on the power - nothing, no clicks, no hum, no lights, no buzz, no boom boom

What I have tested so far:
Opened the amp and pulled out the power module, tested the push button fuse on the back and the power switch on the front of the case, both work.
Testing the power plug on the back of the module I noticed the hot and common prongs have almost no resistance between them (is this normal?)
With the power module plugged in, the push button fuse bypassed, and the power switch connected, I am getting 0 volts from any of the prongs that feed the other boards in the amp. There is no power leaving the secondary board.
I started testing components that can be tested and found a blown fuse F2 .160ASB (see picture).
Peavey CS800s Fuse.jpg
Peavey CS800s Fuse.jpg (395.51 KiB) Viewed 902 times
Should I replace the fuse and test again or is there likely something else that made the fuse blow?
Is it safe to bypass that fuse for testing?
What else would you test, and how?
Is the fuse something you would order from Peavey, or a component supplier?

Any help is appreciated.

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Re: CS800s Amplifier Power Module Died

Post by FreeFallin » Thu Sep 10, 2020 2:39 pm

Update: I ordered a couple of fuses from Mouser -

I also called Peavey directly I talked to Chris and asked for schematics or a service manual. He was great, he emailed me a schematic right away. It is a lot clearer and newer than the free one I found online and I could see the circut better.

The blown fuse is on the EMI board and hooked to the secondary side of a transforme. When I tested the output of the transformer which according to the datasheet i found here - https://www.tamuracorp.com/clientupload ... X-130B.pdf

It is supposed to output 12 volts, but when i plugged in the module, the voltage read 8 volts and over the next 60 seconds slowly rose to over 80 volts. The primary side seems to be getting a steady 120v so I think the transformer is what blew the fuse.

I just ordered a new one here, since Mouser is out of stock due to COVID. https://www.digikey.com/products/en?key ... D%E2%80%8E

What else should I be testing here while I wait for parts to arrive?

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Re: CS800s Amplifier Power Module Died

Post by Dookie » Thu Sep 10, 2020 7:00 pm

I'd check the Tempsisters on the power amp board. They are designed to go open (Break) if the amp is overheated and "maybe" if too much voltage is applied to the board. I can look tomorrow if you need the exact part number. They look like a Loop of clear plastic. Think of a clear speaker cable wire, a little bigger than a tooth pick around. Inside this clear plastic is the Tempsister. Keep the clear plastic to put the new Tempsister in. Normally when they fail the bad amp channel won't click on and the fan stays on high speed. If too much voltage was applied it may be possible that the board heated up enough for these to fail as well. Worth a quick check anyway. Again if the amp starts up with the fans going fast this is one of the signs these are bad. I've pushed down on the top of the loop to temporarily allow current to flow and the amp channel came on and the fan slowed down. (do this only if your trained properly to do this with a isolated probe etc.) Not a hard repair really. An hour or so.

Let us know how the repair goes.


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