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M-90a power protect problem

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I have an M-90a imported from Japan that looks like it's spent time in a river with how corroded it is, I got it for cheap so it is what it is, but I'd like to see if I can't fix it. The unit powers on but immediately enters protection mode. I have a step down transformer I'm using to power it so I know it's not because of over voltage. Obviously being in protect mode makes the unit non functional, and I'm unsure if that's why the displays receive absolutely no signal when an input is applied or if there's something on the input side that's screwed up. Before I tear this thing apart looking for shorts I wanted to see if there's any common failure points I should test and how to test them. I'm well aware that it could be any matter of things with the condition it's in, but if y'all can just point me in the right direction I'd appreciate it, thank you.
 
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I've already taken the liberty of checking PA0016 on one side and the voltages on pin 8 and 14 look to be in spec, I'll be doing the other IC today. Made a stupid mistake while testing the other one, followed a guide with poor instructions and touched two pins together that I shouldn't have, blew fuse FU1 on the fuse board located right next to the power cable. It blew with such ferocity it flashed. Hopefully no damage to anything else internally but I wouldn't be surprised, I'm aware its my own stupidity for not triple checking what I'm doing that's gotten me where I'm at. Not the end of the world though, this unit really looks like it's spent time at the bottom of the ocean, worst Urushi I've ever seen. Got it cheap

Transistors seem to be alright? They test well for the most part, it does not overload when reversing the polarity when testing base to emitter, but base to collector seems to overload properly? Seems all of them do that so not sure that's an issue. They all test to the same value when polarity is correct for PNP and NPN. However I did notice that for the NPNs testing overload resistance took AGES as it gradually built resistance incredibly slowly. Perhaps switching speed has dramatically fallen off with age?

Finally, I have noted that some resistors show an open circuit on the amplifier board and there's a diode that shows a fluctuating resistance while all other diodes of the same kind test stable. So at least there's something to go off of there and I believe that's where ill start. I think I'll start road mapping all the resistors the show an open circuit when I get home from work today and see if there's any correlation between them.
 
Pins 8 and 14 checked near perfect on side b with a difference of 0.03. on side a however I was getting full rail voltage to the chip! Great! So predrivers are blown, I'll replace those and the chip, check all surround resistors and diodes and replace any of those that need replacing as well, and hopefully that's my issue
 
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