Once cleaned all damaged parts I made photos of each chip position in order to always have a visual representation of the trucks behind the new sockets. I signed the IC position and it’s location on the PCB. Here some examples:
Then I socketed and replaced resistors and filters.
And then Kynar Wire!
Plugging the board I had a good surprise because the game started BUT after few seconds the vectors hide for a while.
Running the self test I have the following errors:
- 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
Actually not so bad.
All the RAMs/ROM (but BBU RAM) share the VECTOR ADDRESS BUS, from SMEM0 to SMEM9 controlled by 74157 in positions K3, L3, M3.
MAIN ADDRESS BUS (MA0..9) and PROGRAM ADDRESS BUS (SEQA0..9) are connected to these 74157
I can see BBU RAM (5101) uses the MAIN ADDRESS BUS too, so I’ll check if S4 pins 1, 2, 3, 4, 5, 6, 7 and 21 are correctly on the bus and if all lines arrive to 74244 in (P/N)6 (pins 3, 5, 7, 9, 12, 14,16,18). This will be the first test I’ll perform.