are you using LEDs? or normal lamps.
It looks like you have short somewhere

those diodes are a diode bridge to convert AC to DC. I don't think your problem lies there.
However you can always check another bridge if the same thing happens with your tester.
D29 - D32 is the same bridge for matrix A.

edit:
did a quick check on my spare driver board, you have 2 broken diodes. It should not beep but give either around 600 ohms or no measurable value on the multimeter. Check the capacitors if they are still in good health. The top should still be flat.

It could be that when testing with all connectors attached that you measure a short which is in fact your transformer. Did you remove the power driver board while testing or was it still in the pinball machine with all connectors plugged in?

Good luck on that dont think you will succeed without source files of star wars
I am working on building an emulator like nucore but from scratch using qemu (started with mame) and I have it working now. Implementing DCS at the moment.

Hooking into the code using an emulator is easy. However rework of images is impossible. Everything is coming out of the roms with the pointers in the source code.
The emulator makes sure all pixels are at the right mediagx vram location and then dumped to the display.

So if you want to do something with this you must first learn how the real software works.

This will replace the original computer just like nucore does. However the code of nucore has never been released so it is a closed source and it has some drawbacks. Performance is very good though.
Developing my own emulator allows me to have full control over output and input. Not over the graphics being generated by the code of the pinball game itself.
It will allow me to basically control any lamp / solenoid, read any button / switch and act upon such a thing.

Nice work. Looks really good

I installed my own emulator code on my machine and played some games. No problems there. Works really smooth and sound is working with real emulation
This opens doors also for Wizard Blocks owners as this is not possible for nucore emulation. Also the lifetime of pinball 2000 will be extended with my emulator as it is very easy to keep Ubuntu up to date

The ROMs are compiled code and images
To be able to add functionality you need the full source code. Then you can compile it to a new update version. The roms will not change anymore but there is flash Ron on the prism card for compiled updates