Difference between revisions of "Repair help"

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(Simple VRAM error troubleshooting)
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==Video RAM error==
 
==Video RAM error==
*Address between $0000 and $7FFF: Check [[CXK58257]] RAM chips next to [[GPU]]s.
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*Address between $0000 and $7FFF: Check [[CXK58257]] [[VRAM]] chips next to [[GPU]]s.
*Address between $8000 and $86FF: Check [[CXK5814]] RAM chips.
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*Address between $8000 and $86FF: Check [[CXK5814]] VRAM chips.
 
*Read high byte is different: check RAM chip with highest number.
 
*Read high byte is different: check RAM chip with highest number.
 
*Read low byte is different: check RAM chip with lowest number.
 
*Read low byte is different: check RAM chip with lowest number.
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==No sound==
 
==No sound==
 
*Backup RAM corrupt, '''SOUND_STOP''' ($D00046) is non-zero. Clear Backup RAM.
 
*Backup RAM corrupt, '''SOUND_STOP''' ($D00046) is non-zero. Clear Backup RAM.
*[[Power amp]] is dead.
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*[[YM2610]] has no clock, bad control signals (/CS mainly), or dead.
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*[[YM3016]] has cut traces to YM2610, or dead.
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*Low sound level: recap audio section.
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*[[Power amp]] is fried.
 
*Unplugged or faulty [[NEO-CDD boards|NEO-CDD board]].
 
*Unplugged or faulty [[NEO-CDD boards|NEO-CDD board]].
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*Dead op-amps.
  
 
==Z80 error==
 
==Z80 error==
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[[Category:Chips]]
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[[Category:Repairs]]

Revision as of 02:44, 23 December 2015

MVS

Video RAM error

  • Address between $0000 and $7FFF: Check CXK58257 VRAM chips next to GPUs.
  • Address between $8000 and $86FF: Check CXK5814 VRAM 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.
  • YM2610 has no clock, bad control signals (/CS mainly), or dead.
  • YM3016 has cut traces to YM2610, or dead.
  • Low sound level: recap audio section.
  • Power amp is fried.
  • Unplugged or faulty NEO-CDD board.
  • Dead op-amps.

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)