Need help with video display problem with 4 slot

sourdoah · Dec 10, 2005

I got a 4 slot board and was trying out in my 2 slot Neo Geo MVS and got a display problem. Rather than describe the symptoms I thought I post some pictures. I am not getting any error messages and the games play okay on all four slots. I have not looked at the boards yet and thought I would post the problem here before attempting a repair. Maybe it is something simple maybe the board is junk. Appreciate any help.

First post in long time forgive me if I screw it up.

chris1 · Dec 10, 2005

This looks to be a dirty carts...Mobo Connectors are very dirty..
Make sure the jamma edge-harness pins are clean too...

sourdoah · Dec 10, 2005

Thanks for the suggestions.

It is a four slot board with a different game in each and the problem is on every game. Would one dirty slot affect the graphics on the other three.

I will clean the jamma connector and see if that will fix it. I have previously unplug and plugged back in the connector with no charge in the picture. I will post the result.

sourdoah · Dec 10, 2005

Cleaned jamma connector and reinstalled. No change in picture.

channelmaniac · Dec 10, 2005

That's a messed up cartridge connection... not a JAMMA connection problem. Some graphics are screwed and others aren't...

Clean the slots and the carts real well.

RJ

chris1 · Dec 11, 2005

sourdoah said:
Thanks for the suggestions.

It is a four slot board with a different game in each and the problem is on every game. Would one dirty slot affect the graphics on the other three.

I will clean the jamma connector and see if that will fix it. I have previously unplug and plugged back in the connector with no charge in the picture. I will post the result.

Try the cart-mobo cleaning methods here..

http://www.hardmvs.com/html/projects.htm

Otherwise..I think this could be caused by a bad connection between the top and bottom boards of the mobo..
Make sure all the pin ends(white blocks) are sandwitched tight together..
Other:
This IMO is fixable but it may have to be sent out unless you have the tools etc to fix it.

sourdoah · Dec 11, 2005

Cleaned the board slots and the carts thoroughly, problem persists.

I should have time Sunday to open up the boards and see if I can find any bad board connections, broken traces, corrosion damage etc.

Again thanks to all for the help.

SpamYouToDeath · Dec 11, 2005

Hmm... may be a broken trace somewhere. If it's a 4-slot... remove the battery immediately, and check the traces located near it.

sourdoah · Dec 11, 2005

Took apart boards and could not see any problems. The board connectors appear clean and tight, the battery and battery area look good. Anyway put boards back together, no change. Did not remove battery at this time. Is there possible damage under the battery? Bad video chip?

Took one more picture, might show the display problem better.

Thanks all.

Grinwing · Dec 12, 2005

I have a very similar problem with a 4 slot. I haven't had time to dig into it, but am interested in any ideas also. Cleaning was done to no advantage. All four slots and all game carts have the same effect, so it's somewhere on the boards. I haven't seen any bad traces, but haven't gone over it with a fine tooth comb. Will investigate the connecting pins a little closer also to see if I can find anything there.

channelmaniac · Dec 12, 2005

Well, if you could isolate it to either the top or bottom board, it would make your troubleshooting easier...

Do you have any friends nearby with a 4 slot board that will let you try their top board?

RJ

sourdoah · Dec 13, 2005

I don't know anyone with a four slot to test the board with. The repair quest continues. If I learn something I will let you know.

:help:

Razoola · Dec 13, 2005

Its very clear there is a broken trace or pin somewhere. If this problem happens in all 4 slots then the problem is either in the 4 connectors which connect both 4SLOT PCB's together or somewhere on either of the 2 PCB's. There is a thread MLK did that shows all the pins that connect both PCB's.

Its going to be one of the lines that choose the tile to draw, line 0 infact because its clear GFX tiles are repeating instead of drawing the next tile (instead of 01234567 its pulling 00224466.

Raz

ninja maestro · Dec 13, 2005

I dont suppose any of that wisdom applies to the damaged 6 slot I posted pics of before does it? the graphical corruption looks quite similar, however a continuity test failed to provide any real sign of a broken trace as all of them were fine.

Clearly this problem seems to be popping up a little more. :crying:

dogtoy · Dec 14, 2005

try pulling the top board off and powering the board on. Do you get the cross-hatch screen without any errors? Or is the same graphics corruption still there.

How about if you power it up without any carts in the slots?

cheers,
-DT

Urbain03 · Dec 14, 2005

Are you sure that there are no shorted-circuit pins somewhere on your board?

Look at the screen: it's divided into lines and the lines show 2 times the same image. There must be a short circuit near the video processor. Maybe a drop of solder or a piece of wire landed between two pins ?

I once had a very strange sound problem on my AES and it was caused by a tiny, tiny bit of wire that landed on the solder side of the PCB between two pins.

sourdoah · Dec 14, 2005

I have done the test switch "tests": crosshatch pattern, red blue green test, sound test, etc. all are good. And I have powered up with no carts and get the crosshatch pattern undistorted. I don't see any short circuits on boards, the boards show no signs that they have ever been worked on.

I started the post hoping it was something obvious to someone or I was doing something stupid. Sounds like the consensus is that it is likely a broken trace and not a bad chip. When I have some time I will get out my multi-meter and I will inspect the boards more closely for broken traces.

Thanks all

Grinwing · Dec 14, 2005

Popped mine in without a cart and the crosshatch screen looks fine. I had the Super Sidekicks 3 cart in and the title screen looks fine, just the background has lines of missing stuff in it. I will try to get a picture of it to see if mine is chip issue or a trace issue.

Grinwing · Dec 15, 2005

Here are a few pics of what mine is doing.

Any specifics as to where I should start looking is greatly appreciated.

dogtoy · Dec 15, 2005

Check the area around your risers. I have seen 4 slots where the board risers (supports between the two boards) had rubbed parts of traces and either cut them or shorted them to the traces on the bottom board. I guess maybe these boards i saw had their board risers replaced with different ones?

It definitely sound like some problem with the top board, since all the bios functions appear normal on the screen. Somewehere between your cart slots and the main system you have a problem. Are you REALLY positive that the pins on the slots are clean?

Hell, run the top board through the dishwasher (no soap). Might just fix it.

Maybe not I just noticed that it is only sprites which are getting messed up (both of you guys). All the text that is a neogeo font and not a sprite looks perfect. I would look hard at the top board for traces, bad solering, etc. than i would start to look really carefully around all the ram chips that deal with sprites and maybe in grinwings case the palette rams.

cheers,
-DT

channelmaniac · Dec 15, 2005

If you think it is a RAM problem then check the A0 RAM line (Address line zero) for continuity back to the next chip... I'm sitting in an airport so I can't get to mine to see where that line goes... but if A0 is stuck low or if the line to it is shorted or open (the open condition would depend on if the RAM chip would hold the line high or low via internal connections) then that could cause you to get even addresses.

RJ

sourdoah · Dec 18, 2005

Fixed Display Error

Razoola had the problem nailed.

I looked closer at the underside of the board and notice a spot where the board had a small scrape and found a broken trace there. The spot was near the controller ports leading to one of the board's four connectors near those ports. Using a magnifying glass I combed the trace back into place with a sewing needle and tested the board and found everything now works correctly with all four slots.

Thanks to all for the help.

I still need to make the repair permanent. The broken trace is in the middle several closely spaced traces and I am probably not skilled enough with a soldering iron to make the repair myself. I'll probably have a TV repair shop do the job for me.

Again thanks to all

Need help with video display problem with 4 slot

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