Here the problems I had yesterday.
- BBU RAM S4: BAD
- V RAM2 J1 and or (L/M)1: BAD
- V RAM4 (J/K)1 and/or (N/P)1: BAD
- V ROM2 F1: BAD
1 – It was related to a power problem. I can’t understand connecting the oscilloscope ground to the game ground the probe wire becomes hot. Anyway problem solved.
2 – V RAM2: This was the most complex error. The analysis made yesterday had no success but considering now the problem was related to J1 and or (L/M)1 only I pointed my attention to the “Chip enable” circuit. After some tests I could see I forgot to rebuild the track between 7404 in position PR1 PIN 8 to 7432 in position R1 pin 10.
3 – V RAM4: (J/K)1 2114 was faulty. I just replaced it.
4 – V ROM2 F1: ROM was actually bad and I replaced it with a new one.
This is the self-test result. I’m sorry I didn’t manage Z signal 😀 😀 😀
so, PCB now is ok…
What have I to do now?
- No sound to the right speaker
- Monitor (not working)
- Back panel