Hello to the DIYers!
I am somewhere closer to the final stage to complete the F5v3 balanced monoblocks.
I've pre-biased ams with a lab PS, then assembled the amp in a chassis and started it with a variac: after reaching 25% of the nominal voltage my bridge rectifier blew off: traces on the PCB exploded.
My PS is: 800VA 2*27V trafo, 8*47000 uF 40V Sikorel caps, pair of 159ZL 10A 2.5mH inductors.
View attachment 1041171
View attachment 1041168
I decided to disassemble the entire amp and check the PS separately:
1. All the 8 caps are functioning properly, RLC meter shows correct capacitance, after applying 30VDC from the Lab PS all the caps charge well and discharge with bleeder.
2. Next I disconnected rectifiers and applied Lab PS to the positive and negative rails separately, without attaching the ground bus between rails: two separate rails were functioning OK.
3. After I installed the ground Bus between the rails and V+ rail charged properly while V- rail behaved like a short: 0V and max current of the lab PS (left channel on the picture).
4. Next I checked the other power supply (for the second monoblock) in the very same fashion and got the same result: positive rail is OK, negative behaves like a short.
View attachment 1041170
I spent the entire night on it I can't find anything wrong in the wiring or individual components, thus asking for some community opinion on what could go wrong.
I have a lab PS, Variac and high quality multimeter with RLC to check any of the assumptions.
Thanks in advance!