I checked the flat cable and it and the connections seem good. I believe the failed regulator fed the PIC16F917 that drives the display. Maybe the voltage variations have damaged the driver chip?

I have a pair of active speakers hooked to the Mini-I's XLR connectors. The sound comes to the Mini-I from TV through Toslink. I just tested it after the repairs, and the sound works as expected. Volume control, remote, source switching, everything works, it's just the display that doesn't show...

That's exactly what I did. The +12V and -12V regulators were standard L7812CV and L7912CV which I luckily had in my stock from another project. Those weren't necessarily faulty, however. It seems they don't get input unless the whole unit powers on. The +-18V from the transformer is routed to...

I measured the regulators, and the +12V reg shows 0.138V at input and 0.080V at output. The -12V reg shows -0.361V at input and 0.193V at output. Not good. Interestingly, the two +5V regs near the display have 12.00V at their inputs and 4.992V and 4.999V at their outputs, so at least they work...

Thanks anyway. I should have told the fuse was ok in the first place. I measured the +12V and -12V voltage regulators near the transformer (unit powered on). I didn't get a good reading, just a few hundred millivolts, and somewhat fluctuating. I'm going to double-check them later today with a...

Yes, the fuse is ok.

I've had a Matrix Mini-I v.1.82 for a couple of years, and I've been really happy with it, but... ... a while ago, a weird problem with the display appeared. Upon power up the display worked ok, but after a while it showed just gibberish. Took the thing apart, and some of the electrolytic...