MVS busted sound

[Bigblue709]

Like a dummy, I managed to pop something in the sound circuitry by rapidly power cycling my supergun, probably while it was in mono mode.

Everything still runs fine but the unit is totally silent now.

Is this a fixable issue? Surely I'm not the first person to make this mistake.

 

[Kujako]

Most likely it's a blown amplifier. Let's start with what model you have, although pictures always help. The audio section should be clearly marked.

 

[Bigblue709]

Thanks -- it's an MV1FZ. Photos below. I was mistaken earlier, it's not actually totally silent, there is a low buzzing noise that gets louder when I turn the volume pot.

 

[Kujako]

OK, so that is a MV1FZ which can be modified for stereo but out of the box uses mono JAMMA audio. So your super-gun was setup correctly. The amplifier is the HA13001 that looks like it has some rust on the bolts. But the issue could be elsewhere. Do you get the Z80 error when there is a cartridge in the system?

 

[Bigblue709]

Yep, I get the Z80 error when I load a new game off the multi cart. I'm also noticing as I inspect the board that there's a missing component in the circled area, corresponding to the area between the NEO-F0 chip and RAM 10. The board is in rough shape overall but these spots seem still shiny, as if the damage was more recent.

 

[Kujako]

The Z80 error is most often attributed to damage caused by a leaking battery. Something to consider. The damage on the underside is definitely an issue, looks like it's around the SN74AS04N inverter. No idea if that is used in the audio sub-system...
You can check the PCB scans to see what's missing/damaged. https://www.mvs-scans.com/index.php/MV1FZ

 

[Ryoandr]

Batteries don't leak on MV1FZ/1A/1B/1C models as they're lithium.
The missing circled cap is a power bypass cap, it should not cause huge errors. If you want you can replace it with a 100nF ceramic.
Z80 errors can typically be from either Z80 dead (very common), Z80 RAM dead (common), SM1 dead (happens), YM2610 (happens), corroded traces can also be a thing of course ; NEO-D0 and NEO-C1 can also be responsible but should be looked at the very end since they're harder to replace and find.
If you can you should really make or get a diag bios, and a M1 diag card, as it does deeper tests compared to regular bios or unibios.

 

[Bigblue709]

Thanks, both of you, for the tips.

Regarding the diag bios / card -- is there a North American source for these? I do have an EPROM burner but the only cart I have is my multi.

 

[Kujako]

Thanks, both of you, for the tips.

Regarding the diag bios / card -- is there a North American source for these? I do have an EPROM burner but the only cart I have is my multi.

Try just running with the BIOS to start. I know people at times sell the carts, but I had to build my own. I found a bootleg cart that had socketed EPROMs which made it easy. You'll want the cart for the full Z80 testing, but the BIOS mat pinpoint other issues that may be addressable first.

(here's mine)

 

[Ryoandr]

For the M1 test cart you only need a CHA board with a NEO-ZMC (so not a really old game), with the Test M1 and a game S1. If you're a bit handy you can take a game cart, use a 256k EPROM, burn game M1 into lower half, test M1 into upper half, and use a pull up and a jumper to alternate between uses.
While some MVS cart can be pretty cheap so this is a lesser problem, I had to do this for AES as console games are expensive ; I now have a Fatal Fury 2 that can serve both as a test M1 and a full game test.