I now have two Tetris boards. One is named AC-Fried - I accidentally ran AC through the video, (was a ChungHwa monitor isolation problem, thread in monitor section), wrecking its ability to sync, video is scrambled like the olden cable days. Other is Blind Tetris which has been the subject of this thread.
For AC-Fried, I'm walking back from the traces and finding continuity on both sides of a capacitor, having another tetris board is a big help in understanding what is and isn't supposed to be there.
In a pause, I decided to debug the original blind board by swapping some other ICs that were easy and see if anything would change:
Slapstick
2x Pokey
EEProm
CMOS Ram
No change, Still playing blind. The EEProm, when swapped over, didn't even play blind. Putting back the original one for that board returned it to playing blind.
I did notice one IC that is socketed on AC-Fried board, that is soldered straight on Blind Tetris: 137550-001, the SOS custom. MAME code says these are used to generate video signals, which I thought was intriguing. I have a working Rampart that also uses this IC, so I'll do a swap between Rampart's SOS and AC-Fried Tetris to verify that the SOS is not what got cooked on AC-Fried. If I got a working one I'll try to piggy back the SOS on the blind Tetris so see if anything interesting occurs.
For AC-Fried, I'm walking back from the traces and finding continuity on both sides of a capacitor, having another tetris board is a big help in understanding what is and isn't supposed to be there.
In a pause, I decided to debug the original blind board by swapping some other ICs that were easy and see if anything would change:
Slapstick
2x Pokey
EEProm
CMOS Ram
No change, Still playing blind. The EEProm, when swapped over, didn't even play blind. Putting back the original one for that board returned it to playing blind.
I did notice one IC that is socketed on AC-Fried board, that is soldered straight on Blind Tetris: 137550-001, the SOS custom. MAME code says these are used to generate video signals, which I thought was intriguing. I have a working Rampart that also uses this IC, so I'll do a swap between Rampart's SOS and AC-Fried Tetris to verify that the SOS is not what got cooked on AC-Fried. If I got a working one I'll try to piggy back the SOS on the blind Tetris so see if anything interesting occurs.
