Repair help: Difference between revisions
Jump to navigation
Jump to search
(→MVS) |
(Simple VRAM error troubleshooting) |
||
| Line 1: | Line 1: | ||
=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)