MVS neo gep MV-1B graphic problem, help!!

andrew96

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Hi

Have this nice small MV-1B but it has a graphic problem, I have so far changed the video ram 5 and 6 but its exactly the same



it boots ok but when setting dip1 is set then i get this, a good pic taken from a mv1fs is shown for comparison


My bad MV-1B

4.jpg


The screen should look like this, pic from a good MV1FS

1.jpg


here are screens of metal slug 4 when game is running

My Bad MV-1B

6.jpg


The screen should look like this, pic from a good MV1FS

2.jpg


and also

My Bad MV-1B

5.jpg


The screen should look like this. pic from a good MV1FS

3.jpg



as you can see a bit screwed! does anyone have any sugestions on what to go for next? there is no circuits online so a bit stuck!

help!!!
many thanks
Andrew
 
Last edited:
I'd start by checking very carefully for physical gouges to traces, bent pins on customs, or corrosion damage from liquid spills or rodent urine.

The Neo Geo is a very robust system and most of these kinds of issues can be found in the physical damage category.
 
Thankyou both for your quick replys

yes have very very carefully examined the board and traces, it is spotless! very clean, and yes the slot is also very clean!, its like its never been used! no board or trace damage and no fluid either

couple more pics


bad mv1b
7.jpg


good mv1fs
8.jpg
 
Last edited:
The faulty MV-1B board


9.jpg


10.jpg





even the backup battery is perfect, no corrosion there at all, and the correct voltage
 
Did you separate the top and bottom board and clean the two board connectors, yet?

-------------------
NEO-MVH MV1B CHX

http://www.boredstu.com/neogeo/hardware/mv1bchx/mv1bchxmain.html

mv1bchxtoplarge.jpg


mv1bchxbottomlarge.jpg


1: "SW1" - Dipswitches
2: "BT1" - Onboard Backup Battery - 3.V Lithium
3: Edge Connector - This uses a standard JAMMA pinout
4: "MASK 1" - Bios Chip - Toshiba TC531024F - Soldered (surface mounted)
5: "VR1" - Volume Adjustment POT (controls volume for sound running through edge connector)
6: "CN4" - 8 Pin connector for attaching the Irritating Maze Trackball Kit.
 
Did you separate the top and bottom board and clean the two board connectors, yet?

oh yes, there nice and clean and shiney! it lks like the board has never been used! also continunity checked those connectors too, there fine, its not a connector problem, its rock solid! solder is good to

Thankyou for your reply
Andrew
 
One MVS cart slot has holds two boards--a top board and a bottom board (or front and back board depending on how you look at your NEO cart.).

In general, the top cart board is the program board and the bottom cart board is the graphics board.

Your problem seems to be with data communication, either to or from, this bottom cart board (somewhere along the bottom half of the cart slot).

IMHO, it looks like you'll need a probe to find out which chips and data lines are not communicating correctly with the bottom board.

Given the compact, hoizontal design of the MV1B, this looks challenging.

But the idea is to work your way from one side of the bottom cart slot, to the other side, checking data communication. Look for a faulty chip or line on the board side--and fix it.

neo_mv1bSm.jpg


boardmv1b.jpg
 
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