Crest CA18 Preamp issue

[rf7]

I have a Crest CA18 on the bench that the top half of the waveform folds early on one channel. I swapped modules and determined that the issue lies in the preamp PCB. I checked all of the semiconductors and the resistors, and they all measured fine. The rails all measure fine. The PCB is not accessible, so I can't get a scope probe in there. Any ideas for how to chase this down?

crest-ca18-power-amplifier-circuit-diagram.pdf

[Jazz P Bass]

On a hunch I would blame it on the limit circuit.
Specifically, the NE5517 ic.

[rf7]

OK, I'll check that out.

[rf7]

That was it! Thanks Jazz!

[Jazz P Bass]

O/k, can I have half of the hair back that I pulled out on the one that had the same issue?

[rf7]

Sorry, I can't help you with that. It is a tough amp to troubleshoot, because you can't really probe inside those amp modules when they're installed in the chassis. Thanks so much for the help, I really appreciate it!