Does seem a bit odd all of them would read bad even on the low side considering theres not much that could cause excessive current through all diodes simultaneously to damage them all, so I'd double check that meter before plunging into a lot of soldering, something else on the board could also be affecting the readings but apart from the flipflop IC driving that circuit (74htc273) I cant see a component that jumps out at me or rings bells....its a tricky one..... probably wrong and missing something but just my gut feeling

Just for kicks, if you have the board out can I see a pic of the underside in that area?

also, what do they read with the 9 pin connectors removed? any change? not thinking its the diodes but isolating the circuit may help pinpointing a possible culprit.
you are correct in saying in circuit or out can change things, a cap holding charge can be enough to bias a diode or 20...

thanks, nice soldering... hmm nothing strange there...was hoping to see something odd. back to the drawing board....
I'm thinking you have a roasted coil or two... if there are flywheel diodes on them and said diodes test fine disconnected... Its pointing to the coils.
Even if a coil tests fine while not energised, its possible its been overheated and the insulation then breaks down under load thus drawing too much from the driver circuit.... 50v is enough to see that type of thing.

sorry mate, thats all I've got.

Glad you got her going again!

And I gotta say well done, thats not an easy one by any means!
Faulty new components are the worst thing Iv'e encountered in this field, still doesn't spring up as a likely cause in my mind.

Just last week I wasted a few hours on a car audio amplifier with an output circuit "mystery fault"....

14 brand new Irfp4868 fets..... ali express....

10 of em were short circuit between gate drain source, one open on all three legs as well, last one very leaky, and would have killed some other stuff.

first six literally exploded... that's two paired sets replaced in a row + collateral damage of gate resistors and driver transistors before I thought to test the rest of the "brand new, faulty batch" fets.

thought I was going mad!

Apologies for vanishing too, been offline for a while setting up things....

just a thought that your damaged VIA or through hole that your cap leg wasn't contacting is likely due to chasing your tail a few and having extra soldering/unsoldering trying to find the cause... heating and cooling, expansion contraction, VIA fatigues as its through the pcb rather than on the surface and has nowhere to expand to then shrinks when cool and disconnects... had that a few times...

If there was no repeat solder work Id say rare faulty board manufacturing, it does happen, but Id like to rather blame the faulty fets causing extra work still...

I have a grudge against faulty fets. they get me right messed up every darn time!