Rockford Fosgate T2000 problem

the screws are firm; I checked again and I realized that the rectifier diodes D27,D28,D29,D30 etc have +49 fixed and -2.6, -2.8,-3.0 intermittently, with the negative probe connected to the RCA shield, the same with the negative probe connected to B Neg.
 
The rectifiers don't have a ground reference. They float, along with the rails. Initially and at shutdown, you will read the positive voltage but after the amp is producing rail-rail oscillation, the voltage will be near 0 volts.

There should be a direct connection between all of the points with a primary ground symbols (inverted Christmas tree?).

The RCA shield is a different ground.
 
You're right Perry, the ground of the diodes is floating, I checked the voltage at the ends of the copper bars that go through the middle of the toroids and I have 103 volts; all the screws of the aluminum plate are screwed and they are the ones with the image that looks like an inverted tree, note that the protection light flashes to the rhythm of the bass (distortion)