MV1FZ Graphic Problem

batesey

n00b
Joined
Mar 24, 2015
Posts
10
Hey Guys,

After 5 or so years, a house move, family and whatnot, I'm finally back into Neo Geo-ing :-)
I've successfully brought a dead and rusty MV1C back to life and got bitten by the fix it bug!
I really want to extend my learning with electronics and what better way to do that, than repairing my favourite gaming system...Neo Geo :-D

Soooo, last week I purchased an MV1FZ from a dude who said it worked, but with known graphics glitches.
The board arrived last week, along with an MV1A (that's a thread for another time) and I immediately threw it on the test rig to see how it functioned.
EVERYTHING works great, apart from the graphics problem you can see in the pics below.

MV1FZ-01.jpg
MV1FZ-02.jpg
MV1FZ-03.jpg
MV1FZ-04.jpg
MV1FZ-05.jpg

I've done my research...I think. My problems almost looks exactly like the example found here:
https://wiki.neogeodev.org/index.php?title=Graphic_glitches

Something to do with the Lower Address Lines on the C Rom. I think my issue reflects what is written about Address A3, as my mirrored graphics lines look similar to the examples on the neogeodev website.

Previous owner marked the LSPC2 and NEO-B1 chips as possible faults. I really hope not as I don't have a donor board with these chips to do a replacement.

MV1FZ-08.jpg

I'm thinking there is something way simpler at fault, and that's where I'm hoping I can get suggestions from the community.

What I have done so far.
- After my initial test of the board, removed the original Bios and replaced it my my licensed UniBios 4.0...no change in graphics state.
- Bough a TL866II Plus Programmer and made myself an SMKDAN Diagnostics Bios. Was a fun excise as it's not something I've ever done before, No faults found, ALL TESTS PASSED!
- Bought a USB Microscrope and looked over every square centimetre of the board, very diligently, to try and find broken traces, weak solder points and such...Found nothing!
- Looked over all through-hole solder pins on connectors, sockets and caps to make sure there were no shorts...Found nothing!
- Went over ALL traces with a multimeter in continuity mode to make sure all the Connections between the vertical Cart Slot and main board were OK...Everything checks out OK!
- Made sure it wasn't the game I was using to test boards...All good, game works flawlessly in the other 4 MVS Systems that I have here.
- Bought a Logic Probe and started poking around chips to see what noises I could make. Was fun, but as I really don't know what I'm looking for, and where I should be looking, wasn't really beneficial :-D

The board looks almost factory new I think. There was very little in the way of dirt, exorbitant amounts of flux residue...nothing really.
The only thing removed from the board was the battery...and it was a clean removal.

MV1FZ-06.jpg
MV1FZ-07.jpg

Nothing else on the board looks as though it's been tampered with.
There are NO signs of corrosion what so ever.
All Caps look original, in good order, no leaking, no puffing, all look really good.

While I can understand the appeal of continuing to use the system as is (it does make gaming on it more challenging), I'd really like to get it back to an original working state.

Or is this an issue that will likely see no resolution, therefore I've got a nice parts board?

Thoughts anyone, where can I begin?

Cheers,
Batesey
 
Last edited:

daskrabs

Ace Ghost Pilot
10 Year Member
Joined
Aug 23, 2010
Posts
1,313
See here. Looks like you have a "Lower address line" C Rom issue (Sets of 8 rows are mirrored).
 

batesey

n00b
Joined
Mar 24, 2015
Posts
10
See here. Looks like you have a "Lower address line" C Rom issue (Sets of 8 rows are mirrored).

Thanks daskrabs,
That’s the info I already found :-) I was hoping someone might point me in a direction on what to check next. I’m hoping there is a solution to my problem, without needing to change out the LSPC2 and/or Neo-B1 chips.

Cheers,
Batesey
 

daskrabs

Ace Ghost Pilot
10 Year Member
Joined
Aug 23, 2010
Posts
1,313
Thanks daskrabs,
That’s the info I already found :-) I was hoping someone might point me in a direction on what to check next. I’m hoping there is a solution to my problem, without needing to change out the LSPC2 and/or Neo-B1 chips.

Cheers,
Batesey

Sorry, didn't read your whole post. Keep in mind that traces rot on these boards without visual signs.
 

DaisyAge

Galford's Armourer
Joined
Jun 10, 2018
Posts
457
If you end up needing a donor board let me know, I have an MV1FZ for parts.
 

batesey

n00b
Joined
Mar 24, 2015
Posts
10
I would check continuity between the P0-P23 pins on the LSPC2-A2 and the CHA cartridge slot.

https://wiki.neogeodev.org/index.php?title=File:LSPC2-A2_pinout.png
https://wiki.neogeodev.org/index.php?title=MVS_cartridge_pinout

I would start with P19 as suggest by daskrabs link.

Hey ack,

thanks for the suggestion, checked ALL, P0-P23 on the LSPC2-(A3...my chips is marked as an A3).
As you mentioned, started with P19, continuity all the way to the correct pin on cart slot.
Went over all pins with the multimeter 3 more times to be sure...P0-P23 have continuity to the correct pins on the cart slot.
Anywhere else to prod around?
Cheers,
batesey
 

batesey

n00b
Joined
Mar 24, 2015
Posts
10
Sorry, didn't read your whole post. Keep in mind that traces rot on these boards without visual signs.

Hey daskrabs,
yeah, it's got me puzzled, because the board looks brand new. I've gone over the traces and have yet to find one that looks suspect...I'm guessing if I'm getting good, solid continuity across the traces and vias that I'm probing, then all is good right?

If you end up needing a donor board let me know, I have an MV1FZ for parts.

and DaisyAge, thanks for the awesome offer...i'll hit you up when I can narrow down exactly whats required to fix my board...hopefully something simple. What condition is your MV1FZ in and why do you have it as a spares board?

Cheers,
batesey
 
Last edited:

batesey

n00b
Joined
Mar 24, 2015
Posts
10
Hey Guys,

Inspecting the board again and I've found what looks to be a broken tantalum capacitor on the underside of the board. Looks like she's taken quite a hit :-/

MV1FZ-09.jpg

Not saying it has anything to do with my initial problem, but can someone advise, or does someone know a replacement part for this?

Cheers,
batesey
 

DaisyAge

Galford's Armourer
Joined
Jun 10, 2018
Posts
457
Hey daskrabs,
yeah, it's got me puzzled, because the board looks brand new. I've gone over the traces and have yet to find one that looks suspect...I'm guessing if I'm getting good, solid continuity across the traces and vias that I'm probing, then all is good right?



and DaisyAge, thanks for the awesome offer...i'll hit you up when I can narrow down exactly whats required to fix my board...hopefully something simple. What condition is your MV1FZ in and why do you have it as a spares board?

Cheers,
batesey

Has broken traces from someone taking the 68k off wrong, also missing some pallette ram. I bought it as a spare board to repair another one I had at the time.
 

Xian Xi

JammaNationX,
15 Year Member
Joined
Dec 1, 2005
Posts
27,748
It wasn't mentioned but does this happen with multiple games or just this one? Clean your slots, too. There's been countless times people sent me boards to fix and they just weren't cleaned very well.
 

batesey

n00b
Joined
Mar 24, 2015
Posts
10
It wasn't mentioned but does this happen with multiple games or just this one? Clean your slots, too. There's been countless times people sent me boards to fix and they just weren't cleaned very well.

Hi Xian,
Firstly, wow, this is awesome...I've read sooooo many of your post! Thanks very much for your reply to my issue :-) to aswer your question, it was happening to multiple games...
but I've got some really good news concerning this particular unit :-) SHE's FIXED, all working properly again!!! :-D

I knew where the initial issue was and what was casing it, but after double checking at all of the places that other people had posted here, it was by fluke that I found out where the problem was.
I'd hooked up the board again to my supergun and was messing around with it, when I accidentally moved the board while it was running...BAM, the picture came good for a split second, then went back to the mirrored lines of sprites. I got excited, put a bit of pressure on the front right leg of the board again, and BAM, pic was back to normal. AWESOME...must be a loose chip on the board, I thought to myself.

Long story short, after slightly twisting the board to see if any pins on chips moved slightly, I finally isolated a potential issue on LSPC2, but it's funny, because when I checked all the pins on the LSPC2 for continuity, everything checked out OK. So, anyway, I re-flowed all the pins on the LSPC2 chip and am happy to say, I have a brand new looking, fully functioning, original MV-1FZ :-)

Thanks everyone that chimed in on my thread to help me fix the issue.

Cheers,
Batesey
 
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