MVS 1F Crosshatch

[dragonpt]

Hi guys

Got this board in January for 20 eur, since it was pretty much dead.

The usual battery leaking issues (corrosion on traces from 6116)
Both work rams where dead
Several traces around NEO-F0 also patched ( through holes corrosion )



After all the above fixs. the board + game, booted up to crosshatch ... cleaned the cart slots and board contacts, and the board finnaly booted up all my games just fine.

Today, after getting it from storage, again it just boots to crosshatch, cleaned all again several times to no avail.

checked PROG cart pins A1 to A19, continuity is fine to 68K ( 0.5 Ohms)
checked PROG cart pins D0 to D15, continuity is fine (? ) to 68K ( 1.6 Ohms) , same resistance from 68k directly to bottom of the board pins that connect to Cart board

Btw DIP1 is OFF, and it's OK


I Remembered Raz talking about using Unibios Mem Viewer at adress 0x100 when in crosshatch with a cart inserted

The values starting at adress 0x100 should be : 0x4e45 0x4f2d 0x4745 0x4f00

Mine are :

So obvious a data (? ) address isn't ok. And " NEO GEO" has some data missing in there
I just don't know how to translate this, some help would be much appreciated

The game above used is the 161-1 Cart

Thanks

 

[ack]

I'm not sure what to make of that pic. The hex data looks ok, but the ascii side is not displaying the "E"'s.

Mind testing with a legit cart?

 

[dragonpt]

Hi thanks for the help

sure, with Metal Slug ( 1 - original )

Just dunno, why it shows "slot 2" ... it's an 1 slot lol
cheers

Edit: Forgot to tell that Diag bios says all tests passed

 

[ack]

Had to disassemble unibios to see how it could display the correct hex data but the wrong text data.

When its reading the data for the hex values its reading from the address as words, while the text side its re-reading the address as a byte.

You will want to probe the NEO-C1 and NEO-I0 chips. Specifically the ROMOE/ROMOEL/ROMOEU/LDS/UDS signals on the chips. It appears when unibios is trying to read a lower byte of the P rom, OE is not getting enabled on the rom. Probably something along this path LDS => NEO-C1 => ROMOEL => NEO-I0 => ROMOE. I would suspect either LDS or ROMOEL is floating or stuck high.

 

[dragonpt]

ack

Thank you so much to take the time to help me out.

You where totally right, issue was with ROMOEL.

There where a couple Through-Hole Vias near NEO-C1 with intermittent signal, likely rust...

The via in question was connecting NEO-IO (31) ROMOEL --> NEO-C1 (91) ROMOEL
The via next to it, was also intermittent, fixed it as well, to avoid future problems

The connection to NEO-C1 is done on the underside of the board, passing thru several through-hole Vias from NEO-IO --> NEO-C1

... arggg ... already had this rusted vias issue, on this board before on another location. ( First time messing with an 1F ... )

Patching those totally fixed the issue, you nailed it! Thank you my friend, you saved me a ton of time diagnosing the problem.


Unibios Mem Viewer, with the issue fixed:

Thanks ack