mikejmoffitt
Mickey's Coach
- Joined
- Feb 6, 2014
- Posts
- 578
I've been helped a lot by repair logs of others in the past, so I'll write down fixes as I do them.
Model: MV-1C
Symptom: Red haze over some, but not all graphics
Fix: The NEO-GRZ IC had to be replaced. The red channel's MSB was outputting nothing and was tri-stated, causing the DAC's 74LS273 to float high. A NEO-GRZ was harvested from an all-in-one JAMMA PCB.
Model: MV-2
Symptom: Very corrupted flickering sprites; glitchy patterns change as hand is moved over certain traces
Fix: Like many MV-2 systems the battery had corroded nearby traces. In this case, 6 of the 8 lines coming from the NEO-ZMC2 chip had been eaten away. Wires were run to replace these tracks, nearly fixing all problems (see next repair)
Model: MV-2
Symptom: On some but not all sprites overlapping others, flickering pixels would appear at the borders of objects
Fix: Pushing my finger on a few traces near NEO-ZMC2 would make the flickering pixels hold still, but not fix them. Probing with the scope, the EVEN input pin for the NEO-ZMC2 had a strange waveform around 2.5V instead of a series of healthy 0-5V pulses. I followed the signal to a spot on the board where a previous tech had done a "repair" - two wires connected this EVEN signal to the 74LS32 @ 1G's pin 13 and pin 11, which makes no sense to me (that's feeding the OR gate's output back into itself, as well as shorting that output to the EVEN signal...) I removed the crap repair and the board is working 100%.
Model: MV-2
Symptom: Some sounds are missing, some have the wrong instrument, some voices are garbled
Fix: One of the address lines coming from the YM2610 went near the battery, which corroded it. A wire was run to restore this high address line, fixing the audio.
Model: MV-1C
Symptom: Red haze over some, but not all graphics
Fix: The NEO-GRZ IC had to be replaced. The red channel's MSB was outputting nothing and was tri-stated, causing the DAC's 74LS273 to float high. A NEO-GRZ was harvested from an all-in-one JAMMA PCB.
Model: MV-2
Symptom: Very corrupted flickering sprites; glitchy patterns change as hand is moved over certain traces
Fix: Like many MV-2 systems the battery had corroded nearby traces. In this case, 6 of the 8 lines coming from the NEO-ZMC2 chip had been eaten away. Wires were run to replace these tracks, nearly fixing all problems (see next repair)
Model: MV-2
Symptom: On some but not all sprites overlapping others, flickering pixels would appear at the borders of objects
Fix: Pushing my finger on a few traces near NEO-ZMC2 would make the flickering pixels hold still, but not fix them. Probing with the scope, the EVEN input pin for the NEO-ZMC2 had a strange waveform around 2.5V instead of a series of healthy 0-5V pulses. I followed the signal to a spot on the board where a previous tech had done a "repair" - two wires connected this EVEN signal to the 74LS32 @ 1G's pin 13 and pin 11, which makes no sense to me (that's feeding the OR gate's output back into itself, as well as shorting that output to the EVEN signal...) I removed the crap repair and the board is working 100%.
Model: MV-2
Symptom: Some sounds are missing, some have the wrong instrument, some voices are garbled
Fix: One of the address lines coming from the YM2610 went near the battery, which corroded it. A wire was run to restore this high address line, fixing the audio.
