Difference between revisions of "Repair help"
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(Simple VRAM error troubleshooting) |
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| − | + | =MVS= | |
| − | == | + | ==Video RAM error== |
| − | * | + | *Address between $0000 and $7FFF: Check [[CXK58257]] RAM chips next to [[GPU]]s. |
| + | *Address between $8000 and $86FF: Check [[CXK5814]] RAM chips. | ||
| + | *Read high byte is different: check RAM chip with highest number. | ||
| + | *Read low byte is different: check RAM chip with lowest number. | ||
| + | *Read byte stuck to $FF (bad /OE ?), only a few bits different (traces cut ?), random address (floating /OE, /CE ?) | ||
| − | ===Z80 error | + | ==No sound== |
| + | *Backup RAM corrupt, '''SOUND_STOP''' ($D00046) is non-zero. Clear Backup RAM. | ||
| + | *[[Power amp]] is dead. | ||
| + | *Unplugged or faulty [[NEO-CDD boards|NEO-CDD board]]. | ||
| + | |||
| + | ==Z80 error== | ||
Can be caused by bad components / continuity with the following: | Can be caused by bad components / continuity with the following: | ||
Revision as of 04:32, 6 July 2011
MVS
Video RAM error
- Address between $0000 and $7FFF: Check CXK58257 RAM chips next to GPUs.
- Address between $8000 and $86FF: Check CXK5814 RAM chips.
- Read high byte is different: check RAM chip with highest number.
- Read low byte is different: check RAM chip with lowest number.
- Read byte stuck to $FF (bad /OE ?), only a few bits different (traces cut ?), random address (floating /OE, /CE ?)
No sound
- Backup RAM corrupt, SOUND_STOP ($D00046) is non-zero. Clear Backup RAM.
- Power amp is dead.
- Unplugged or faulty NEO-CDD board.
Z80 error
Can be caused by bad components / continuity with the following:
- Z80 <-> SM1
- Z80 <-> RAM
Second generation specific (todo: get pin numbers in a nice table)
- Z80 <-> NEO-D0 (NMI,A2-A4,IORQ)
- Z80 <-> NEO-C1 (Z80 D0-D7)
- NEO-D0 <-> NEO-C1 (Z80R,Z80W,Z80CLR,SDW)
