2 Slot - won't boot past green garble screen

Hi, just received a 2 slot board for my SNK 2 slot cab. This particular board is longer than the one originally in it. Everything on this cab worked great with the other board. However, when I connect this board, all I can get is the green garbled mess of a screen that you usually get prior to the familiar Neo-Geo logo/chime screen.

This new board is supposed to be in working order, and the guy I purchased from seems like he's on the up and up.


What I've tried:
Disconnecting and reconnecting Jamma Harness
Tried booting with/without memory card inserted
Tried booting with/without credit LED boards attached
Tried multiple games - specifically, known working carts in my library.
Tried booting with Dip switch #1 ON and OFF

Any suggestions here? The board looks very clean except the pad covering the solder side near the credit LED panels has been removed. Pic attached. Now that I look at it more closely, the corrosion appears to be under a couple of RAM chips. I believer they are RAM chips. They are marked "Toshiba TD62083AP 9136K" on top. Other than that, there isn't a spot on the thing. It's not dusty/dirty and doesn't look like it is "too clean" like someone was trying to hide something.

Check Dip #8

Sometimes, people leave it stuck on pause.

Failed to elaborate on my dip settings.

Also tried booting with all dips set to OFF.

Thanks for the reply.

Check the 5 volts at the board (not the power supply), if its below 5 volts its likely the cause of the problem.

I believe it to be the original power supply (gray metal box). Never looked at it too closely to see if it has adjustable 5v. Will check that tonight.

Let me ask you this, would it make sense for one board to work and the next one not work if the 5v is the problem? Perhaps with the different layout of this larger 2 slot board, it is requiring more. I guess it does make sense now.

kb9wvv said:

Perhaps with the different layout of this larger 2 slot board, it is requiring more. I guess it does make sense now.

Click to expand...

Exactly.

The more current a board set draws, the more voltage drop in the harness. Thats why its important to measure at the board and not the PSU

It could also be a due to a calander error, as in some cases it can produce this situation. Try this...

Turn on ALL 8 DIP switches and power on. You should see a WORKRAM test message. Now turn all 8 DIPs to off while the unit is still on, that will stop the test and allow the unit to continue booting... tell us what you see now.

Raz

As a side note, I see it has the original nicad battery fitted. Its a good idea to replace that before it leaks. (it has nothing to do with the boot up problem btw)

ttooddddyy said:

As a side note, I see it has the original nicad battery fitted. Its a good idea to replace that before it leaks. (it has nothing to do with the boot up problem btw)

Click to expand...

My 2 slot still has the original nicad battery. Is it really that important to change it? What should I change it to? I think there was a thread about it a while ago. I'll have to look it up.

kb9wvv said:

The board looks very clean except the pad covering the solder side near the credit LED panels has been removed. Pic attached. Now that I look at it more closely, the corrosion appears to be under a couple of RAM chips. I believer they are RAM chips. They are marked "Toshiba TD62083AP 9136K" on top. Other than that, there isn't a spot on the thing. It's not dusty/dirty and doesn't look like it is "too clean" like someone was trying to hide something.

Click to expand...

Those aren't RAM chips, they're the drivers for the EL panel and credit displays. Basically they are useless for the board operation, you could pull them off and the board (that is a working board) would still work fine. However, just behind these chips there is the calendar chip (4990) and its crystal so I agree with Raz that it could be a problem with the calendar chip connections. You should remove all the remaining foam and clean the whole area (use a toothpick to remove that white residue) so you can check the connections.

OK. Could not locate any kind of adjustment on the power supply. Skipped that for now.

Next, I started picking at the crust and tried to remove some. I'm fresh out of the cleaner with the brush that I got from the Rat Shack. Anyway, now instead of the green screen I get "Calendar Error" displayed on the screen. MKL, was right on the money.

The question is, what do I do now? I'll be searching the forums later this afternoon.

A Universe Bios will alow a system to boot past this error so that would be a work around to allow games to play without actually fixing the fault.

As to actually fixing the fault I expect MKL or ttooddddyy will know some things to try.

Raz

Thanks, Raz and everyone.

Still "Calendar Error". Going to be sending this one back. Probably a bad trace somewhere.

This pic shows the connections of the 4990 calendar chip on a 2-slot. Other motherboards are the same except they may have a different chip than the NEO-F0 which is an SNK custom chip. The 74HC32 is located very far from the calendar chip, near the backup battery so that is a very long trace particularly prone to damage. A fixed value capacitor may be found in place of the trimmer capacitor.

http://img485.imageshack.us/img485/4576/2slotcalendar0fl.png

The 4990 datasheet:
http://www.ortodoxism.ro/datasheets/nec/UPD4990AC.pdf