Neo Geo MV-1 Display Issues

dysproseum

Member
Joined
Sep 9, 2010
Messages
35
Reaction score
0
Location
Orlando, Florida
I just bought a Neo Geo MV-1 motherboard on ebay, connected it to a JAMMA cabinet and it's not starting up. Its only outputs garbage characters to the screen.

Notes:

- This cabinet works with other JAMMA PCBs
- The board produces the same issue in other machines where a Neo Geo MV-1 works fine with a JAMMA harness
- Same result with any number of cartridges or without one inserted
- JAMMA harness appears to be wired correctly for all required pins on both systems
- Some continuity testing was done in areas that looked problematic but no issues found

Pics of display output and mobo are shown here:
http://dysproseum.com/transfer/neogeo/

What do you guys recommend I do next?
 
Does it play sounds from the carts or is it totally dead?

If it is totally dead, do you get a "click click click" sound from the speakers?

How bad did the battery leak on the board?
 
Me and dysproseum live by each other and we've both been tackling this one so I'll chime in-

-Board powers up to that screen, makes no sound at all. No "click of death" or anything.
-Battery looks good, no corrosion or leaking.
-No signs of bad traces, board is very clean overall. We did probe around for a bit nothing immediate was found in continuity or anything like that.
-Tried several carts, all of which work on my own MV-1 and same result for all.

Ryan
 
If you flip the power off & on does the stuff on the screen ever change?
 
No, it's always basically the same output of random characters in the same color...
What color?


Did you guys already clean the edge connectors on the PCB? I've had PCB's that didn't work and all it took to get them going was a quick cleaning with a q-tip and some alcohol.

Try cleaning the edge connector and hooking up the mobo without a cartridge inserted, you should get the crosshatch pattern if the mobo is working. You can also check the underside of the PCB to see if any pins are bent and touching. If this doesn't get it going then you might want to ship it out to Channelmaniac to fix it for you.
 
We cleaned the edge connectors with alcohol, q-tips, and the pencil eraser method. Nothing appears out of sorts on either side of the board.

The characters that show up are pink & white. Result is the same with or without a cartridge inserted.
 
Yea, we gave the board a real good cleaning on all edge connectors, cleaned the bios rom, pulled off the cart board and checked the pins. Haven't tried it without a cart in it, i know the screen you're talking about though. Dave check to see if that comes up.

Actually- another obvious one i didnt think of! There is a dip setting for 'stop mode' which freezes the screen, its DIP #8, make sure that is off. Documented on page 8 here:

http://www.crazykong.com/manuals/NeoGeoMV1.man.pdf

Ryan
 
Yea, we gave the board a real good cleaning on all edge connectors, cleaned the bios rom, pulled off the cart board and checked the pins. Haven't tried it without a cart in it, i know the screen you're talking about though. Dave check to see if that comes up.

Actually- another obvious one i didnt think of! There is a dip setting for 'stop mode' which freezes the screen, its DIP #8, make sure that is off. Documented on page 8 here:

http://www.crazykong.com/manuals/NeoGeoMV1.man.pdf

Ryan

Yea DIP switches were all off, same results with any of them on or off...
 
DIP #8 won't cause that issue. It'll still go through the normal startup screens and after the green screen it would go black and freeze if #8 was on.

Sounds like you have a serious issue with the board. If there was a RAM issue the watchdog circuit should be hammering the reset line over and over. The would cause the clicking sound through the speakers and a jerk of the data on the screen at the same time. But since that's not happening, the only thing I can think of is a bad failure such as a chipset chip or the CPU itself.

What chip do you have in the BIOS socket? Is it installed correctly? What's written on it?

RJ
 
DIP #8 won't cause that issue. It'll still go through the normal startup screens and after the green screen it would go black and freeze if #8 was on.

Sounds like you have a serious issue with the board. If there was a RAM issue the watchdog circuit should be hammering the reset line over and over. The would cause the clicking sound through the speakers and a jerk of the data on the screen at the same time. But since that's not happening, the only thing I can think of is a bad failure such as a chipset chip or the CPU itself.

What chip do you have in the BIOS socket? Is it installed correctly? What's written on it?

RJ

Great question! I thought the BIOS was installed correctly, but i flipped it around and tried it that way... Got the repeated clicking noise and some larger blinking patterns on the screen!

The BIOS chip reads:

TOSHIBA 9048EAI
TC531024P-15
SP-U2
C472 JAPAN
 
OK...

You may just have a fried BIOS chip... Battery corrosion that messes up the chip select signals to the backup RAM, bad backup RAM, bad work RAM, gouged traces, or a bad BIOS chip are the most likely causes for the click of death issue.

But, anything that keeps the system from booting can cause it.
 
Did you try the BIOS from the bad board in the good one? If it's bad then you'll need to troubleshoot with the good BIOS chip in the board.

If there are no gouged traces or battery damage then it's time to break out the digital multimeter and check for bad traces between the CPU, BIOS, and both the backup and work RAM.

The RAM is 8 bit and the CPU is 16 bit so one RAM sits at bits 1-8 and the other at 9-16. You'll find that the data lines for one backup RAM connects to one work RAM and then to either the lower or upper 8 bits of the 16 bit data bus on the BIOS ROM and the CPU so don't get confused when the data lines don't match on all 4 of those RAMs. It's by design.

After that, use a logic probe and check the chip enable lines on the work RAM and backup RAM. If something is messed up on those signals then it will cause the system to not boot.

If that's not it then the next step is to replace the surface mount work and backup RAM.
 
Back
Top Bottom