Here is the service manual for the PS-400 from the Crown Audio website:
https://www.crownaudio.com/en/site_elements/ps-400-pl4-service-manual
https://www.crownaudio.com/en/site_elements/ps-400-pl4-service-manual
Thanks man but I just found one at https://schematics.ca . It has free schematic diagram downloads for just about every piece of gear in my band. such as guitar amps, vintage tube amps, musical gear like keyboards and effects pedals and repair manuals. A must for touring musicians (like me) to have schematics for their gear in case you get in trouble while on the road. https://schematics-free.com has a lot of great free audio schematics as well.