Peavey CS-800s 1 channel working

[llecount]

Hey all

I've pulled an old Peavey CS800s out of storage with plans to utilize it in an installation. This amp has sat in storage for years, and was here since before I was hired on at my current job.
I don't know it's history other than its current operation.
I need to be able to bridge both channels to run a 15" subwoofer.
Upon powering on the amp, the fans go to full speed (and remain there), both channel's DDT lights illuminate for a quick second, and the power indicator for Channel B lights up. The power indicator for Channel A does not turn on. Channel A obviously has no output to a speaker when an input signal is applied.
Channel B works just fine.
I've seen many others with these problems while searching for repair information, however they are mostly on the older model of CS800 amplifiers, and the internal designs are slightly different.
I'm not an experienced technician, but I know the basics, and I have a Fluke 187 DMM at my disposal to use in testing.
Where do I need to start in looking for a method of repair?
Thanks!
Luke

[Enzo]

The CS800S is not slightly different from the old CS800, it is totally different. The S on the end stands for "switcher", meaning the amp has a switching power supply. The old ones had a plain old linear supply with huge power transformer.

You have a working channel, so the switcher should be working. However, be aware that a switching power supply (herafter referred to as SMPS for switch mode power supply) rectifies the mains directly - 300v of DC with all the current the wall outlet can provide. These are extremely dangerous to work in if you don;t know what you are doing.

COntact Peavey customer service and ask for the schematics. Ask also for the diagnostic procedure documentation, yuo can't just bring these up on a variac.


As to diagnostics, I'd start with low voltage power supplies in the bad channel.

[llecount]

Just wanted to reply to say that I have resolved the problem.
I analyzed the A channel board and found a small thermal resistor on the heatsink fins that was broken. After some further research, I found that a broken thermal resistor will cause the fans to immediately go to high speed upon powering up the amplifier, and will cause the channel not to activate itself.
I sourced the parts directly from Peavey for around $5. I replaced the one bad thermal resistor (or as peavey called it, a thermsistor), placed the board back in the amp, and everything worked fine again when I powered it on. Both channels powered up/worked, and the fans maintained their low speeds until required to speed up.