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No sound on MV1B

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bodgit

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Picked up another MV1B, thought it was working fine however noticed some games didn't have audio, but some did and then with some experimentation found some games had slightly broken audio. For example, Xeno Crisis seemed to have all sounds, whereas not a peep out of Metal Slug and Garou was somewhere in the middle with some channels working. However now no games have sound so feels like something intermittent has gotten worse.

Anyway, got hold of a NeoBiosMasta so I could replace the BIOS and popped in the diagnostic BIOS and test cart and holding down B+D get this:
IMG_4231.jpeg

Seems consistently those values. Also, the warbling notes do play but the last note holds and never stops so there's just a solid tone.

Thinking it's either the Z80 and/or the RAM7. Thoughts?
 
Do you get any beep codes when you run the diag bios + test cart?
 
I believe Xeno Crisis used ADPCM for all music and sound effects, so that could be a clue.
 
bodgit said:
Yes, I do, and the last beep remains stuck on. I'll record the sequence if it helps?
Click to expand...
yeah if you can. Also just to confirm you are using the 0.19a02 m1 rom and not the original 0.19 m1? I forgot if 0.19a02 bios is backwards compatible with a 0.19 m1 rom.
 
ack said:
Also just to confirm you are using the 0.19a02 m1 rom and not the original 0.19 m1?
Click to expand...
I couldn't honestly remember so cracked open the cart and verified against your 0.19a02 download, all good.

Here we go:

Sounds like high-low-hiiiiiigh; that last beep stays on until I power off. I also realised I was being stupid and holding down A+D instead of B+D, (blame the CD controller), so actually with B+D held down I get a slightly different response:

IMG_4237.JPG


The actual value changes from FA to 41, but still expects C3. I also went through a few of the other tests and the only other thing I noticed is that hard dips 7 & 8 don't register, but 1-6 are fine. I wonder if that means the NEO-BUF next to the dips has gone bad, would that interfere with the audio comms?
 
Communication between the 68k and z80 cpus happens via the NEO-SDR-T chip.

An actual value of 41 on that screen should have printed an additional error message, but sure why it didn't.

41 is what the z80 would send if it detects a crc issue with the diag m1 rom. I would check connectivity between the z80 and the cart slot, and from the cart slot to the m1 rom. Perhaps you have a floating address line.
 
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