PCB Repair Logs 1942
1942
 |
|
| PCB Image | Reserved |
|---|---|
| Pin Out | Reserved |
Repairer: VectorGlow
Forum Thread: 1942 PCB Repair
Symptom: Background graphics corrupted – tiles are being duplicated vertically in approx. 1 inch rows
Cure: Pin 11 of LS86 at 10J stuck low (on the lower board) - replaced
Symptom: board is ‘dead’, garbage *briefly* on screen on power on but then screen goes blank. Setting Test Mode on gives a static screen of garbage but won’t run any tests.
Diagnosis: Checked all EPROMs – okay. Checked all RAM – okay. Used a logic probe on the 74LS138 at 10L and found that pin 10 was floating and pins 11, 12 and 13 were all High (should be Pulsing). Tried piggy-backing a 74LS138 onto the same IC at 10L, and the board fired right up.
Cure: Socketed and replaced 74LS138 at 10L
Symptom: When board was cold, on power up the ‘bar’ near the bottom of the screen would sometimes glitch with garbage characters appearing over it. This stopped glitching after a few seconds, and during gameplay there were hardly any noticeable glitches.
Diagnosis: Determined that the two 2114’s at 9H and 10H on board 2 were responsible for the onscreen sprites, so tried piggy-backing good 2114’s onto them one at a time. Found that the 2114 at 10H was suspect
Cure: Socketed and replaced 2114 at 10H
Symptom: Board booting up but won’t coin up, etc and resets when trying to run attract mode
Cure: Bad 6116/TMM2016 at location A9 ? (chip nearest ROMs) on CPU board
Symptom: Sprites replaced by random bits of other sprites
Cure: Bad 2114 RAM at location H10 on video board
Symptom: Sprites mis-positioned and broken up
Cure: Bad 2114 RAM at location H9 on video board
Symptom: No background displayed
Cure: Bad LS138 at E11 (near edge connector on top board) where pin 14 goes to pin 1 of the Ls377 at location A8 (just below the 6 (or 3) background graphics EPROMs on the lower board
Symptom: Dotted lines across parts of the screen
Cure: Bad 2148/6148 at location F2
Symptom: Boardset powers on and plays okay, all graphics okay BUT random garbage text present in many areas
Cure: Bad LS367 at location H1 on the CPU board
Symptom: No sound, just a hiss. No input to sound amp (Capcom original, top board)
Cure: Bad outputs on LS138 at E9 – replaced
Problem: Text corrupting, appearing in the wrong places, etc (Capcom original top board)
Cure: All outputs on the LS157 at E1 stuck low – replaced
Symptom: All sprites extremely blocky and unrecognisable
Diagnosis: Checked the 6 sprite EPROMs on the lower board and then the chips around them – found that pin 9 on the four LS194’s was ‘dead’. Traced this back to the top board where it was found that all the outputs on the LS74 at location K8 were dead
Cure: Replaced faulty LS74 at location K8
