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Battery is dead and has some corrosion on its legs. I've removed it and scratched a bit the area to solder in case I find a replacement one. Luckily there weren't any connections on the lower part. The original one was: Sealed Ni-Cd Rechargeable Battery GS Saft Ltd. Japan GB 50H-2 2.4V 50mAh Lot no. 069GD5 bottom.jpg (3,023,283 bytes) top.jpg (3,333,363 bytes) |
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FDD are TEAC FD-55BR, with jumpers in: FG --> Ground bridge between board and metal D0 --> Disk select 0 IU --> In-Use (technically not used but I could be wrong) RY --> Disk Ready signal on pin 34 FDD1: Tested in an old 486 pc + Greaseweazle; it works. FDD2: Tested in same old 486 + Greaseweazle; seems that carriage return sensor is broken, a GP1S55. PC-88 won't boot FDD1 either way. |
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Tried to connect through RS-232C with xdisk2 but TransDisk outputs "Couldn't make comminucation with sub system!" (sic). Hence I guess the D780C-1 (floppy controller) is not working as it should, or any trace is broken from/to it. Checked voltage and it's correct (+5V on pin 11, GND on pin 29). |
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LC36 (near Mouse port, ZJSC-R47-121) blew up. |
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Running "memtest88" through RS-232 turns screen blank when starts with "Disk RAM #0", which I guess it's IC18. Removed it; no results. Removed D780C-1; no results. Put a replacement of D780C-1; no results. |
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Reflowed all four gate arrays; no results. |
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Replaced track 0 sensor (Sharp GP1S55) with a GP1S52 (I couldn't find the same model); FDD2 working again. IMG_7116.JPG (1,833,938 bytes) |
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Tried so far: - checked caps - memtest88 through RS-232C - making my own asm code and trying pokes - trying to convert other asm programs I found to run them through RS-232C - reflowing four gate arrays (nearly breaking one leg from one and two from other) - all different combinations of removing/putting different RAM/SubCPU/MainCPU - trying to understand different activity with the oscilloscope in several points I'm so mentally tired so I'll put it apart for parts. |
- Anonymous
