Crest Pro-Lite 7.5 Bad Channel Problem - early clipping indicated and very low output

This forum is for talking about all kinds of Peavey power amplifiers.
Post Reply
glitterskulls
New Member
Posts: 3
Joined: Thu Mar 09, 2023 9:40 am

Crest Pro-Lite 7.5 Bad Channel Problem - early clipping indicated and very low output

Post by glitterskulls » Thu Mar 09, 2023 10:07 am

Hey there, I have a Crest Pro-Lite 7.5 Amplifier with an existing channel problem on my bench that was given to me by a friend. Input B and Output B appear to work correctly. Input A has an issue - when given the same signal on both channels, Input A appears to trigger ACL LED to turn on about 12-13db below Channel B. In other words, Channel A appears to clip at a much lower volume level than Channel B.

When I have a speaker plugged in I'm getting almost zero volume out of Channel A, maybe a very faint sound. Even when the clip indicator on the channel is close to triggering. I've tried calling the Peavy service center today but haven't been able to get through. Techs near me listed as Peavey service centers don't want to work on this amplifier, and understandably so because it has a lot of surface-mount parts.

I've cleaned out the amplifier of dust quite thoroughly with compressed air, cleaned connectors on the main board with rubbing alcohol and reseated them. Visual inspection shows nothing really out of the ordinary. I haven't got access to the underside of the main board as it has these plastic clips holding it in and I didn't want to break them trying to get in. Might be some dust still hiding under there.

I'm quite handy with electronics as a hobbyist. I've built dozens of eurorack modules and done a lot of soldering and desoldering, but I'm not great with understanding and diagnosing circuits. I can use a multimeter and follow directions. So does anyone have any information that could help me tackle this? It's weird that there appears to be a problem that is affecting both the input section and the output section of the same channel.

I could try swapping the connectors for the channel gain potentiometers and if the problem moves with them that would be the culprit. Seems like a long shot if the output section is not working right either though. Anyway, thanks for listening to my story. I'm posting here to hopefully find a solution and help others who might have similar issues.

-Cheers, Chris, Glitter Skulls, Ithaca Underground & Microtones Collective, Ithaca, NY

RCColer
Member
Posts: 14
Joined: Tue Jun 09, 2015 4:30 pm

Re: Crest Pro-Lite 7.5 Bad Channel Problem - early clipping indicated and very low output

Post by RCColer » Sat Jun 03, 2023 4:07 am

I’ve had the exact same problem. I wonder what it could be?? Has anyone reached to you?

User avatar
dak
Member
Posts: 428
Joined: Fri Dec 24, 2021 7:20 am
Location: Germany

Re: Crest Pro-Lite 7.5 Bad Channel Problem - early clipping indicated and very low output

Post by dak » Sat Jun 03, 2023 5:42 am

glitterskulls wrote:
Thu Mar 09, 2023 10:07 am
I've cleaned out the amplifier of dust quite thoroughly with compressed air, cleaned connectors on the main board with rubbing alcohol and reseated them. Visual inspection shows nothing really out of the ordinary. I haven't got access to the underside of the main board as it has these plastic clips holding it in and I didn't want to break them trying to get in. Might be some dust still hiding under there.
Without picture it is hard to tell, but some plastic clips are snap-in, and you can squeeze them to fit through the board holes again.

The symptom may fit with high frequency oscillation which would make circuit analysis non-trivial.

glitterskulls
New Member
Posts: 3
Joined: Thu Mar 09, 2023 9:40 am

Re: Crest Pro-Lite 7.5 Bad Channel Problem - early clipping indicated and very low output

Post by glitterskulls » Sat Jun 03, 2023 8:14 am

I was able to reach someone at the Peavey Service center who gave me instructions on how to send the amp in. I didnt bother to describe the problem since full diagnosis over the phone is unlikely, and they seemed very busy. But they were nice and confirmed they will work on the pro lites which is good. I have one local electronic tech genius who's offered to take a look. If that doesnt go well I will send it to Peavey.

RCColer
Member
Posts: 14
Joined: Tue Jun 09, 2015 4:30 pm

Re: Crest Pro-Lite 7.5 Bad Channel Problem - early clipping indicated and very low output

Post by RCColer » Wed Jul 12, 2023 3:20 pm

Has Peavey reached out to you on what the issue is? Wasn't sure if they got to it yet.

glitterskulls
New Member
Posts: 3
Joined: Thu Mar 09, 2023 9:40 am

Re: Crest Pro-Lite 7.5 Bad Channel Problem - early clipping indicated and very low output

Post by glitterskulls » Mon Aug 14, 2023 11:49 am

I've been a bit busy so just got around to shipping the thing to Peavey. They got back to me within 1 week after receiving the unit. Invoice says they fixed Channel A, Replaced a 6.2v Diode, Touched up solder and lubed pots all for $90 plus shipping back to me in NY around $20.
Screen Shot 2023-08-14 at 12.48.27 PM.png
Screen Shot 2023-08-14 at 12.48.27 PM.png (744.06 KiB) Viewed 1831 times

Post Reply