littlecharlie
Quiz Detective

- Joined
- Jan 10, 2018
- Posts
- 87
I have an original MV1B that when booting some specific games, it shows the following message:
MVS SLOT CHECK
VER2.20 99/11/01
M1-ROM ERROR
This is the error I get with my original Metal Slug 3. The exact same message appers on MS3 when using the multicart 161 in 1.
After this message, the game plays:
- Perfectly (video and sound) on my original cart
- perfect video but randomly the sound is completely missing on the 161 cart. After reboot (1, 2 or 3 times) the game plays good (video and sound).
I don't own any other original game that shows this message, but in the 161 cart there are other games that show it (like Sengoku 3).
Apart from these specific games, the rest plays just fine (no message, sound good).
So, when booting with the diag bios, I get an error:
And I've tested the Z80, and I get the sound corresponding to this error:
---------------------------------
Z80 isn't receiving the expected data from the 68k communication I/O port. Most likely an issue with the Z80 data bus or control signal trace to the chips that control the port (NEO-C1, NEO-D0).
The MV1B doesn't have a NEO-C1 or NEO-DO, but instead a NEO-SDR, so I've tested continuity of D0-D7 and IORQ, everything fine.
Soooo, I've probed the Z80 (and compared with another working mv1b) and the only suspicious signal is INT, that it is supposed to be pulsing, but, when I get no sound, it is stuck low.
As per the schematics, this signal comes from the YM2610.
But the YM2610 can't be the problem because I've interchanged the upper board of the MV1B (the one with the cart connector and the YM2610) with the upper board of my other MV1B, and the problem is still there.
Any ideas?
MVS SLOT CHECK
VER2.20 99/11/01
M1-ROM ERROR
This is the error I get with my original Metal Slug 3. The exact same message appers on MS3 when using the multicart 161 in 1.
After this message, the game plays:
- Perfectly (video and sound) on my original cart
- perfect video but randomly the sound is completely missing on the 161 cart. After reboot (1, 2 or 3 times) the game plays good (video and sound).
I don't own any other original game that shows this message, but in the 161 cart there are other games that show it (like Sengoku 3).
Apart from these specific games, the rest plays just fine (no message, sound good).
So, when booting with the diag bios, I get an error:

And I've tested the Z80, and I get the sound corresponding to this error:
---------------------------------
Z80<->68k COMM. ERROR (DATA)
Z80 isn't receiving the expected data from the 68k communication I/O port. Most likely an issue with the Z80 data bus or control signal trace to the chips that control the port (NEO-C1, NEO-D0).
- Z80 D0~D7 → NEO-C1 SD0~SD7
- Z80 IORQ (20) → NEO-D0 IORQ (37)
- NEO-D0 SDZ80R (41), SDZ80W (43) → NEO-C1 SDZ80R (84), SDZ80W (85)
The MV1B doesn't have a NEO-C1 or NEO-DO, but instead a NEO-SDR, so I've tested continuity of D0-D7 and IORQ, everything fine.
Soooo, I've probed the Z80 (and compared with another working mv1b) and the only suspicious signal is INT, that it is supposed to be pulsing, but, when I get no sound, it is stuck low.
As per the schematics, this signal comes from the YM2610.
But the YM2610 can't be the problem because I've interchanged the upper board of the MV1B (the one with the cart connector and the YM2610) with the upper board of my other MV1B, and the problem is still there.
Any ideas?