Peavey CS 200x Power Amp - only channel B working

[tonecat]

Hello Everyone,
I am working on a friends CS 200X and only channel B is working. I have requested a schematic from Peavey. While I am waiting for it, I thought I would post what I have found to see if anyone has any ideas. Channel A has no DC on output, it is not tripping the circuit breaker, and it is getting power to the board. When I hook up a sig gen and speaker to it and turn it on, I get a pop through the speaker like it is trying to work, but then no sound. When I shut it off, after about 1 second, I can hear the sig gens input fading out through the speaker. I don't think this is an output problem because I can hear some sound when turning it on and off. Its almost like it is going into protection mode or something. The DDT light on the front panel is not lit up. Does anyone have any ideas? Hopefully I will get the schematic today from Peavey so I can see what is what. Any help would be appreciated!! Thanks!!

[tonecat]

Hello Again Forum Members,
I finally have a schematic for the amp. Thanks to the folks at Peavey!! I'm still not super familiar with these solid state amps so if anyone can point me in the right direction as far as troubleshooting this thing with the symptoms I described in my first post, I would greatly appreciate it. Enzo, are you out there? You have helped me in the past and I have been able to fix every amp that has come my way with your guidance. Thanks for all the help in the past!! Maybe you could give some pointers on this one also? Anyway, everybody have a great weekend!!

[Enzo]

First things first. Make sure the bridge/stereo switch is set to stereo.

This has a speaker impedance switch? Check that for open contacts. And look for signal at the output circuitry, in case the speaker relay contacts are not making it.

Remove U102,any help? Leave it out until we are through anyway.

Apply a signal to the input and trace it through. Got signal at U100 -1, at the top of the volume control, at the wiper of the volume control, at U101-1, at U101-7?

[tonecat]

Thanks for the reply Enzo!! I wasn't able to work on the amp over the weekend. I will have a look at it tonight and go through the checklist that you gave me. I'll report my findings later tonight. Thanks Again!!

[tonecat]

Got it figured out. It was just a bad input pot. Thanks for the troubleshooting tips Enzo. It is nice to have some pointers when you don't know exactly what your doing and that is what makes these forums so helpful. With the advice and ideas of others, someone like myself who is not an electical engineer can still fix these things. Got lucky on this one. We'll see what happens with the next one. Thanks to Enzo and the forums again!!

[micri5446]

ahhhh...the 'ol bad pot trick......things that make you go ....hmmmm

[gmsingh]

Does the schematic show where the DDT control is?

[Enzo]

No, there is no DDT control. DDT is hard wired, part of the circuit. The compression threshold is the clipping threshold.

[gmsingh]

The owner's manual says the DDT is internally defeatable.

[Enzo]

What it says is that if you don;t want to have it, you can have a technician remove it. There is no switch, we defeat it by removing parts.

I can't imagine why you would want to defeat it, it doesn't affect the sound until clipping is reached, and unless you like blown drivers, you don;t want clipping.