Did this one for Andy (U72)
Board had numerous faults. Board would not boot, kept re-setting or giving RAM error (to bottom board at 2H I think). Swapped in an known working bottom board and got same error so knew that was BS.
Here's the complete run down:
1) Replaced socket at 2L and re-attached loosening legs to 06XX chip
2) ROM 7 at 3E bad and replaced, Fujitsu 2732 to blame for that one.
This fixed the top board. Next the bottom board.
3) Replaced 2200 ohm resistor pack at RM4 had been bent completely over which knackered it
4) Replaced socket at 4M for 05XX (star field chip)
Really bad contacts.
5) Dug out 6M 6148 RAM chip socket after finding 2 broken traces on the removed sprite RAM - one trace iffy beneath so patched a line in. Someone had ripped out four 8147 RAM (6J to 6M) and replaced with a single 6148 at 6H but did a really bad job of it.
6) Decided to replace the other 4 custom sockets to ensure longevity of the PCB, no point getting the board back a week or two later
Now booting but to a screen with odd blue lines
Blue lines would disappear upon manipulation of the harness. Cleaned edge harness and did various other things which appeared to switch lines on and off. Left this running for a long while and all lines disappeared. Knew this was now heat related - this is a nightmare and one of the most PITA faults to track down.
However, on a hunch from another weird fault I've had with a different PCB decided to clean and reseat all the 2114 RAMs between 3E and 3L and moved their positions up one. Fault almost disappeared. Pulled chips again and noticed some of the legs were not completely straight - straightened the lot (making very sure) and all blue lines disappear
Now done - Happy days.
jonhughes2017-09-22 21:27:22
Board had numerous faults. Board would not boot, kept re-setting or giving RAM error (to bottom board at 2H I think). Swapped in an known working bottom board and got same error so knew that was BS.
Here's the complete run down:
1) Replaced socket at 2L and re-attached loosening legs to 06XX chip
2) ROM 7 at 3E bad and replaced, Fujitsu 2732 to blame for that one.
This fixed the top board. Next the bottom board.
3) Replaced 2200 ohm resistor pack at RM4 had been bent completely over which knackered it
4) Replaced socket at 4M for 05XX (star field chip)
Really bad contacts.
5) Dug out 6M 6148 RAM chip socket after finding 2 broken traces on the removed sprite RAM - one trace iffy beneath so patched a line in. Someone had ripped out four 8147 RAM (6J to 6M) and replaced with a single 6148 at 6H but did a really bad job of it.
6) Decided to replace the other 4 custom sockets to ensure longevity of the PCB, no point getting the board back a week or two later
Now booting but to a screen with odd blue lines
Blue lines would disappear upon manipulation of the harness. Cleaned edge harness and did various other things which appeared to switch lines on and off. Left this running for a long while and all lines disappeared. Knew this was now heat related - this is a nightmare and one of the most PITA faults to track down.
However, on a hunch from another weird fault I've had with a different PCB decided to clean and reseat all the 2114 RAMs between 3E and 3L and moved their positions up one. Fault almost disappeared. Pulled chips again and noticed some of the legs were not completely straight - straightened the lot (making very sure) and all blue lines disappear
Now done - Happy days.
jonhughes2017-09-22 21:27:22
