Be aware that the repinning is easily a couple of hours, even with the proper tools. Much, much longer if you don't have the proper tools.

Also, I had an issue repinning our Solar Ride where the extractor tool didn't fit the original housings. I just wound up ordering replacement housings for those I hadn't managed to repin the hard way, cut the original connectors off and stripped, pinned and seated into the new housings. Marco Specialties actually carries most of them, although in two cases I had to order one position larger than required, and cut out a key in each one (still keyed though), as they didn't have the exact size in stock. The extractor does fit the new housings, interestingly enough, so I suspect the specification changed slightly, or the original housings had some dimensional shift.

Here's the link. You want the single sided, .156 inch types. http://www.marcospecialties.com/pinball-parts/ELEC-CON?S_CAT2=GOTTLIEB

A couple of things to try:

Is the connection between the sound board and the speaker solid? And is the voltage to the sound board consistent? The former should be reasonably easy to check, the latter requires at least a multimeter, and quite possibly an oscilloscope so you can actually watch the waveform.

https://www.greatplainselectronics.com/products.asp?cat=77

This is where I got the connector housings for our Solar Ride. As near as I can tell, the specification for the connectors was changed slightly at some point after the System 1 was made, and the extraction tool also changed. My extraction tool fit the new housings just fine, but not the old housings. It was cheaper (time and money) for me to just CUT the wires off as close as possible, strip the ends, and crimp/install into the new housings.

As a note, a couple of the connectors, you'll have to order one position larger, and cut one of the "keys" out so that it will fit. It'll still be keyed enough that you can't really mess it up unless you misinstall one of the points.

All the fuses are standard.

My recommendation would be to attempt a power up with various pieces disconnected. Start with all boards disconnected, then move to connect power supply board, MPU, driver, displays, and sound, powering each time. Basically, you want to see at which point the fuse pops, so you can narrow down which piece is the culprit.