Find a new repair shop! A good tech should be able to troubleshoot down to the root cause of a failure and test the system so that you have either a rock solid repair or a good reason why the amp is not worth repairing. This is totally different than simply finding the bad/blown part and just replacing it.
The techs literally rebuilt the power supply section, the poor thing was just too beat. Like, was spitting fire out the back. Tragic, really.