Neo Geo MVH z80 Error

troxel

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Had a calendar error with battery corrosion. Cleaned corrosion and changed the crystal. Now I am getting a z80 error message. Replaced z80 with a z80a and had no change. Reading other post and to quote RJ:
"The Z80 ERROR message is a catch all for the main CPU (68K) not being able to talk to the sound subsystem. It could be a bad trace, Z80 CPU, SRAM IC, sound ROM, or YM2610 sound chip.

Most likely a bad trace or dead Z80. SNK had a habit of using Z80 chips instead of the Z80A that it needed."
Is there a connection pinout somewhere for the z80? Any other ideas?
 
You do still have a (good) battery connected right? They mentioned the SRAM IC as a possibility, which may do weird things if it doesn't have its upkeep voltage.

Also, examine the board for any damage, particularly on the traces between the 68K and the Z80. Use a multimeter to confirm that traces between the two are actually connecting the pins they lead to.
 
Which model board?

If it's an MV1 or one of the 1 slot boards with the Z80 and 6116 SRAM near the battery then you are stuck checking every trace and plated thru hole in the area to see which ones got eaten up by the battery leaking.

There aren't any traces connecting the Z80 directly to the 68K. Also, any chip in the digital part of the sound circuit that affects the Z80's normal operation will cause this error... the 6116 SRAM, the sound ROM, and even the YM2610, but that one is a rare failure...

RJ
 
By far the most likely is bad tracks, NeoGeo boards are renowned for it, have seen boards with no signs of battery corrosion, that look in utterly mint condition yet still have bad tracks, it seems to be corosion inside the vias, I guess the laquering process failed to coat them.
 
True! So VERY true!

SNK had some crappy manufacturing processes and didn't clean the boards too well. You'll find all kinds of gunk down in the vias.

RJ
 
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