Any suggestions for fixing graphical glitch?

Hi, I bought a 4 slot board a couple of months ago that has been working (for the most part; sometimes took a couple of boot-ups to get a game going) and a couple of days ago, I went to test a couple of games I just received and they didn't work. I tried my other games which I knew worked fine and ran into the same problem: when I turn on the machine with a cart inserted in any slot, I get a black or blue screen with a few blocks of graphics (random placement. Today, my wife and I cleaned the board completely as well as all the carts, and I get the same graphics glitch. Any ideas?

Thanks to everyone here in advance for any advice.

Btw, the machine makes a 'bleebing' sound a few times when I turn it on or shut it down (think starting up a car and it wheezes a few times before starting) and I'm curious if that's normal.

Thanks!

-Renmauzo

Can you provide a picture? Does your 4-slot pass all of the self-checks when the system is started with no game inserted (or DIP 1 set)? Are you sure your power supply is up to the task of powering the 4-slot? MV-4 units can draw over 5 amps and the newer MV-4F units more like 3 amps.

The PSU hooked up right now was the one it came with and the games were working until a couple of days ago, but I had purchased a new one to install as I'm working on restoring the cab. That said, I hadn't done anything differently than usual and this problem came out of nowhere (I only get a black screen when no cart is inserted) but as I said, I would often have to reboot the machine once or twice to get a game going (I would see a cross-hatch screen, or a green screen, etc., and then the game would load correctly on the 2nd or 3rd try), but I will post a picture shortly as you've suggested.

My wife is getting pretty pissed with this machine considering the cost of the restoration and the games so far, and the cost of this replacement board, since I had about a half dozen different RAM errors on the board it came with. It feels like it never ends; I haven't even played any games yet (the CP has been in pieces while I had the metal re-done, and was waiting on new sticks and buttons) so I've only seen the games I have working in demo mode. *sigh*

Thank you very much for taking the time out to try and help me, I really appreciate it! I'll get some pics up later this afternoon.

I'm sorry about your wife's frustration - my wife can definitely relate (she hates all the circuit boards and stuff I have lying around). Anyway, I think a good place to start would be the BIOS chip. Take it out of the socket, inspect it for corrosion or any other type of crud. Give the pins of the BIOS chip a good cleaning and also the socket that it fits in. Replace the BIOS by firmly pressing it back into the socket. Then look at the battery to see if it is leaking. Check for corrosion around the board under the battery and see if it is differently colored there. After a while the 3.6V NiCd batteries have a nasty habbit of leaking chemicals that penetrate into the board and eventually start eating traces.

I would just try to get it running without a game inserted. If it is easier, you can even remove the top board entirely for now. The crosshatch screen is what you want to see - it means that the system has tested the RAM, Z80, card reader, etc... and not found any problems. From the crosshatch screen you can go through other tests for the monitor, sound, buttons, and such by pressing the P1 start button.

By the way, is this a MV-4 or a MV-4F?

Here are those pics; the first 2 are with no cart(s) inserted, the next 2 are with 2 carts inserted in various slots.

I'm still going to look at the BIOS chip as you suggested, and go from there, but I did check for battery leakage yesterday when I was cleaning up the board (the dirt was pretty caked on) and they all look to be in tip top shape.

Thanks again for the help and suggestions!

Edit: Almost forgot to answer your question: the board says NEO-MVH SLOT 4 on it near the first slot.

FWIW I've seen this exact same screen when a friend of mine had his cart inserted backwards. I'm not saying that's the problem, just saying that whatever causes that could be at play here, something in a slot maybe? Dunno.

Alright, so I removed the BIOS chip, gently sanded it with fine grit, cleaned all the contacts, and gave the board one more look for any dirt I might have missed from the other day, and although I get the same as screens 3 and 4 with carts in the slots, with no cart inserted, I now get the cross hatch screen. Any help to take this the rest of the way would be much appreciated. Thanks!

The crosshatch screen is good. Were you able to cycle through the tests for monitor, buttons, sound, and calendar?

An issue with MV-4 boards is that a lot of the time they work fine in self-test mode but don't work at all when a game is inserted. Check the voltage on the +5volt line. If your power supply is adjustable then try increasing the voltage a bit by bit from 5.0 volts to 5.1, 5.2, ... up to about 5.6 volts and see if it comes to life. MV-4 boards often need a bump in the voltage to get games to work, but don't go above 5.8 volts.

You have probaby done this already, but make sure the connectors between the upper board and lower board are clean and make good contact.

I think I have it sorted out!!! I was trying the board again about 10 minutes ago and I started adjusting the PCB feet, teh screen then went through a few different colours as I was doing this and then I got the Neo Geo start-up screen. I tested 3 different carts, shutting down the machine and re-booting each time and they all came on in one shot. Does the positioning of the PCB feet have that much effect? I noticed that many people selling their boards on the forum will list specifically when their board has had 'new PCB feet' put on, but I didn't think that made much difference. If anyone could shed some light on this, that would be awesome.

If you see this mjs256, I just want to give you a huge shout out for your help; I learned about the BIOS chip because of you, and you made the effort to help me out which i greatly appreciate. I'll finally be able to play my cab for the first time this weekend once I re-assemble the control panel, so I am super stoked!!!

Again, I'm curious about this PCB feet thing, so if anyone can offer insight on this, that would be greatly appreciated.

Hey thanks for the shout out! I am glad the board is working. As long as it is working fine I would just say play it and enjoy it! However the plastic PCB feet should have no effect at all on how the board functions. If you changed the location or tightened or loosened the feet and it made a difference with how the board works then you likely have a popped solder joint somewhere - a joint that sometimes makes contact and sometimes does not, depending on the temperature, humidity, the phase of the moon, etc... When you changed the feet you probably made the board flex in a slightly different way - enough to make contact at the popped solder joint.

As long as it works fine I'd say just go with it, but if the problem comes back, try puching down on the large surface mounted ICs enough to flex the board just a little and see if that makes a difference. You may need to reflow the solder of the SMDs. From your symptoms I would start with the LSPC chip.