I have a MPU board which had serious corrosion due to batteries.
Removed all bad components, cleaned the board, fixed dead traces and placed sockets and new components.
After soldering everything booted the machine with Leon ROM.
After booting blanking led stayed off and 5V and PIA stayed on. Also PST1 (PST518a - or in my case a MCP120) got hot and after contacting the store they were sure the right MCP120 was sent. Couldn't get any step further so checked the MCP120 myself and it seems I received a wrong version: the D1 instead of the G1. Twisted two legs and after that the blanking led turned on and off and also the PIA turned on and off. So far so good it seemed.
Tested all PIA's and they were fine as well.
After tested some stuff and powering the board on and off a couple of times the relay gets energized but there is no click. You can feel it getting energized though.
Ohm test (relay still soldered on the board) gave a result of 39.2 Ohms so that "seems okay" (I know I should desolder it to be sure 100% it's okay).
Replaced Q80(2n4401) and the diode (parallel over the coil) but same result.
Measured pin 11 and 12 of 7402 (12b) and they are pulsing high which should result in a low pin 13 and it does.
Soldered a lightbulb on pin 13 and 14 of the relay (parallel) but no light so it seems there is either not enough power to energize the relay or the pulse is too short.
What is also weird: my logic probe (Elenco LP-560) pulse led pulses with the testprogram...
Used a heavy duty powersupply for the 5V and a lab powersupply with both the same results.
With the original game ROM the blanking led stays off, 5v and PIA are on. This would indicate there still is a problem on the board....
Ordered a new ROM since I'm not sure this one is okay.
1) is it normal the logic probe pulses with the testprogram? (never used the Leon test ROM before but I cannot explain why the LP pulses);
2) i assume the relay should have a loud click when performing this test? I assume it should but....;
3) any hints on how to continue?