WHY ALL OF YOU DON'T StOP MESSING AROUND ?
The bad chip doesn't mean its forceably bad !
TYhe first thing to do is to take off the suspicious SIMM, and then, clean the contacs with a soft pen eraser (gum), clean the contacts with a soft brush, and put it back to place.
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The IC8 shit....
Don't mess with the power supply adjustment !
ALL THIS HAS TO BE DONE WITH MACHINE OFF AND MAINS PLUG DISCONNECTED
First : put some pot cleaner (for electronics) on the power supply adjustment pot.
Remember the position of the pot and, with a screwdriver, turn it back and forth a few times, to end by putting it at the original position
Take a voltmeter and plug it relaibly to the 5V on the cards somewhere.
Put power on and measure, if needed, by adjusting the pot, set to 5.05 V
Shut the machine down.
Take a 3-4 feet yellow cable, prepare both sides for soldering, on side of the cable will go soldererd on one of the yellow cables coimposing the harness of cables going to the card cage, the other side of the cable will go to pin 8 of IC 3. It will bring +5V to the relay circuitry and everything will work fine.
Some idiots just connect the pins of the relay, wich means it make a huge "Booom" when you power-up. Normally, this 5V is brought by the leftmost of the four 20 pin flat cables going to the jack board.
I have done this mod for dozens of times.
If you have any doubt, just lest me know, don't feel you are going to look stupid.