Spy Hunter: Sound Board Interface Error

dgersic

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I'm working on a Spy Hunter that boots and plays ok, except for no sound. I get music, just no sound effects. On boot, I get the "Sound Board Interface Error" message. I've read that this could be caused by the 6116 RAM on the SSIO, and wanted to test it before blindly replacing it. The game's diagnostics don't seem to do anything (no response to changing switches on SW3). I found Clay's SSIO test ROM, burned it to a 2532 to match the other ROM on the board, and installed it.

I can't tell if it's working or not, as I'm not getting anything at the LED. Even the "LED test" does nothing. I've checked the DIP switch bank with a meter, and they all seem to be working.

Any idea what would cause the LED not to work?
 
The 2 ribbon cables carry the main CPU's address/data bus onto SSIO to read a few switches, and write to a dual-ported ram to generate sounds. I'm looking at a different MCR schematic and I don't see SW3... but if anything works, this signal path is probably clear.

I've used that sound test ROM and can vouch that it should work. Use your DMM to check if it's trying to turn on the LED (maybe the light is just dead?). Otherwise, suspect a dead z80 or something killing the address/data bus on that side that prevents the sound test code from running at all. Maybe you have a stuck A/D line thanks to the 74-670, 74-374, or 74-138 that selects them?
 
The 2 ribbon cables carry the main CPU's address/data bus onto SSIO to read a few switches, and write to a dual-ported ram to generate sounds. I'm looking at a different MCR schematic and I don't see SW3... but if anything works, this signal path is probably clear.

I've replaced the ribbon cables, so I'm pretty sure that they're good. I'll double check them to be sure, though. Sw3 is physically located between J1 and J2 on the board. The manual says it's located at "D14". Strangely, a quick look at the SSIO schematics doesn't seem to show it. Maybe I'm just not seeing it, though I see Sw1 and Sw2.


I've used that sound test ROM and can vouch that it should work. Use your DMM to check if it's trying to turn on the LED (maybe the light is just dead?). Otherwise, suspect a dead z80 or something killing the address/data bus on that side that prevents the sound test code from running at all. Maybe you have a stuck A/D line thanks to the 74-670, 74-374, or 74-138 that selects them?

Ok, thanks. Yeah, it could be the LED itself, which would be an easy fix. I haven't dug in to the board yet. I guess I have some work to do on this one.
 
It's most likely the Z-80 CPU, or the RAM on the SSIO.
-Mark

I'm not familiar with the MCR board set, but would a dead Z80 not kill the entire SSIO board? Is the SSIO's processor doing anything other than the sound effects?
 
I'm not familiar with the MCR board set, but would a dead Z80 not kill the entire SSIO board? Is the SSIO's processor doing anything other than the sound effects?

Somewhat answering my own question, maybe. Re-reading the "MCR II Troubleshooting Guide" again, it sounds like I can rule out the Z80. I can play the game, using the "credit" button inside the game. I don't have the coin door hooked up yet. But if the coin switches work, they are read via the SSIO, so the Z80 should be working. I'm assuming that the "credit" button is also read via the SSIO. Right?

I can also swap the Z80s between the CPU and SSIO boards, which will prove that the Z80 works. That leaves me with the RAM being the next most likely candidate.
 
But if the coin switches work, they are read via the SSIO, so the Z80 should be working. I'm assuming that the "credit" button is also read via the SSIO. Right?

With the coin door connected, one of the two coin switches work, and the play meter on the door is pulsed, so at least some of the SSIO functions seem to be working.
 
The Z-80 is used to process the sounds on the SSIO. You can remove it- and the button inputs would still work. In fact some games only use this PCB for the inputs, as they have a separate sound board.
 
The Z-80 is used to process the sounds on the SSIO. You can remove it- and the button inputs would still work. In fact some games only use this PCB for the inputs, as they have a separate sound board.

I put a logic probe on the Z80, and it's dead. The clock is running, but there's no activity at all on the Addr or Data buses. Looks like replacing that's the next step.
 
SoI don't have the coin door hooked up yet. But if the coin switches work, they are read via the SSIO, so the Z80 should be working. I'm assuming that the "credit" button is also read via the SSIO. Right?
Nope -- as tec9 mentioned the SSIO z80 is only for generating sounds. There's a RAM so the main CPU can command it to play a sound and can read the status.

Things like coin switches are physically on the SSIO PCB but they're still on the main CPU's bus and can be read directly. You can see this on the schematic because each chip hooks up to the BS Data Bus (sound side) or the Bu DataB Bus (main cpu side).
 
I have the same problem with my sounds. Did anyone on this thread ever resolve this with a working solution? I don't see where anyone posted that they fixed the sound effects problem. Thanks.
 
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