Problem with MV1B SLOT check

[littlecharlie]

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<->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?

 

[BIG BEAR]

That message comes up when the M1 chip is not making a good connection in the slot.
The cartridge contacts and or cartridge slot contacts(examine the areas on the left and right side of that daughter board that are exposed as well) needs to be cleaned.
BB

 

[littlecharlie]

Understood, but I've used another mv1b upper board (from another fully working mv1b board), and I still have the problem.

Anyway, I've thoroughly cleaned the cart slot and the main/upper board connectors, no difference.

I'm rather convinced it's not a problem with the cart slot or the connection between the upper and main board ....

 

[BIG BEAR]

Burn a new m1 for your MS3 and replace the old one.
BB

 

[littlecharlie]

The MS3 cart should not be the problem, since it works perfectly in my other MVS boards.

And additionally, when playing MS3 in the 161 cart it also shows this error, so I think it's definitely the main MV1B board.

I've checked again with diag bios and z80 testing (while pressing B & D), and I get this error:

I've checked traces going from the upper board to the main board of the MV1B, havent found any cut traces.

I've replaced z80 and the 2kx8 SRAM, and the result is the same ....

 

[daskrabs]

Are you using a diagnostic test cart in conjunction with the Diag BIOS to verify the Z80? I think that's needed, otherwise it gets skipped. IIRC, all you need is the P-ROM on a MVS board that has at least an S-ROM populated.

 

[littlecharlie]

Yep, the screen from my last post is using the test cart to test the Z80.

And I hear 6 bips, corresponding to 001100, which according to smkdan site is a "Z80<->68k COMM. ERROR (DATA)"

So my guess now is that the NEO-SDR (acts as intermediate between z80 and 68k) is faulty, and that would mean that I can't go no further.

The strange thing is that:

• when using original carts (I have MS, MS2, MSX, MS3, Real bout FF, Shock troopers), the games play fine video and audio and I see no "MVS SLOT CHECK" message. MS3 is the exception (but after the message the game is just fine)
• when using the 161 cart I get the "MVS SLOT CHECK" message in several games (MS3, SENGOKU 3, MATRIMELEE) and the sound is missing, but after several reboots, the sound appears again ....

 

[kuze]

Have you tried clearing the backup ram?

 

[littlecharlie]

Have you tried clearing the backup ram?

yes, no changes

 

[BIG BEAR]

So these carts run perfectly in your other MV1B?
I've received this message with my CHAFI0 carts on various systems and it was due to not making good contact between the cart and slot OR a bad M1
BB

 

[littlecharlie]

Yes, all my originals carts (including the MS3) and also the 161 cart play fine (without the message) in my other MV1B and other boards I have (MV1A, MV1T and MV2F).

The problem occurs only with this specific MV1B board.

I don't own an original Sengoku 3 o Matrimele, but seeing that these games show the message in the 161 cart, I would say that the message will also appear with these original carts in my faulty MV1B.

 

[Neo Alec]

How did you clean the carts and slots? Try a contact cleaner like Deoxit D5, and wipe it good with a credit card and thin towel covered in the stuff.

 

[BIG BEAR]

How did you clean the carts and slots? Try a contact cleaner like Deoxit D5, and wipe it good with a credit card and thin towel covered in the stuff.

He stated it's not the daughter board because when he swaps those parts between both of his mv1b motherboards,he only gets the error on one of the mv1b main boards.
BB

 

[littlecharlie]

Thanks Alec, I already did this the first thing (I used a contact cleaner similar to deoxit), but it's as BB says, I've tried using a daughter board from another working MV1B, and the problem remains.

And viceversa, the main board of the working MV1B with the daughter board of the faulty MV1B shows no message and plays just fine.

So definitely something wrong with the main board.