Dumb Neo Geo Question (maybe 2)

I'm not sure if this helps at all, but with 3 count bout the neo geo splash screen always looks like the picture I posted. With nam 1975, sometime it looks fine, sometimes it looks like 3 count bout. I'll do a re heat to all the solder points and check traces between the chips, thanks for the advice everyone! I'll keep you all posted

one other thing, not sure if this helps either, my neo geo is a 5 volt model missing the cap at 100p and has a daughter board.

 

With the serial number you can know the version. If that have the daughter board it must be a low serial and output mono from the back connector maybe version one.

 

The Serial Number is: 015686 Also, once this is fixed I'll be installing a uni-bios 3.0 chip into the machine. I did notice that the uni-bios has a test feature, would that help diagnosis the problem? If not I wont add the chip in till after the problems I already have are resolved. I don't wanna throw another potential issue into the stew

 

You definitely have a NEO-AES board (first release), so check between the LSPC-A0 and PRO-C0 chips.

The Uni-BIOS can't diagnose it either--only a continuity tester, with perhaps the aid of a logic probe or more tediously an oscilloscope.

These are the probable connections to check:

lspc.129 -- c0.121
lspc.130 -- c0.122
lspc.131 -- c0.124
lspc.132 -- c0.125

lspc.133 -- c0.105
lspc.134 -- c0.106
lspc.135 -- c0.107
lspc.136 -- c0.108

lspc.137 -- c0.123
lspc.138 -- c0.126

I'm not exactly sure which signal is which, so I can't narrow it down further.

 

Okay, per suggestion, I tested the pins on the chips to see if the connect the other chips. Of the list you sent...

lspc.129 -- c0.121
lspc.130 -- c0.122
lspc.131 -- c0.124
lspc.132 -- c0.125

lspc.133 -- c0.105
lspc.134 -- c0.106
lspc.135 -- c0.107
lspc.136 -- c0.108

lspc.137 -- c0.123
lspc.138 -- c0.126

They all make contact just fine. so thats not the issue. more digging required. Also, what dose the daughter board do for this unit? power or a video board?

I also got a 3rd game in, Magician Lord, the "NEO GEO" splash looks the same with the scrambled graphics and most of the game looks scrambled as well. So far of the 3 games (3 Count Bout, Nam-1975, and now M. Lord) this one looks the worse.

A couple quick ideas. Would it be worth wild to do a complete capacitor replacement? or would caps not play into graphic issues? Also my 1K resistor located between LS05 and another LS05 chip, near the very back edge of the machine, shows some blue crust coming from it, not a lot, looks like slight corrosion but not really?

I'll take some High Resolution (the highest that my camera will allow) pictures of the entire board and upload them to a public folder on my drop box account. Maybe that will help?

I really do appreciate everyones feedback on this forum and cannot thank you enough for the regular updates you all have been posting ^-^

 

The capacitors aren't the problem, nor is the resistor (it's related to the 68K system, if it were bad the 68K would crash immediately). This is a trace issue, or a slight possibility for PRO-C0 chip damage. I'm almost certain the culprit is a control signal from the LSPC that drives the C0's line buffers. Not much else dynamically changes sprite to sprite, at least in any way that fits the sprite distortion.

There are a few more LSPC -> C0 connections but I don't have them handy and I don't think they're related to the line buffers. Maybe you're reading a good connection but there's a bad joint to the leg. Did you reflow the C0's pads with some flux?

 

I just reflowed all the pins from...
LSPC-A0
PRO-B0
PRO-C0

Also before all of those reflows, I reflowed all the pins from the cart connector, which then resulted in Magician Lord looking much much better. Actually on M. Lord, the Neo Geo splash screen looks perfect, as dose the games title screen, but still some problems with the player sprites and looks like some enemy sprites.
Also the Neo Geo Splash screen looks perfect on NAM 1975 as well since the connector reflow, but still has sprite issues. 3Count Bout still no improvements.

is it possible to find/make a replacement chip if the chip is bad? Or am I sol if this the case?

 

I'm tempted to pretend its a Xbox 360 and just hit the board with a heat gun. Would this ruin anything? I'll take care to not melt any plastic

 

That's a bad idea and could likely ruin your system.

 

To be fair it's close to ruined anyway though, if it's a corrosion issue it's probably gonna get worse over time anyway.

If you're 100% certain that there are no more small scale tests/jobs you can do I'd say go for it, just prepare yourself for a potential funeral and have a few caps handy just incase they go bang. Watch your eyes too!

 

I wouldn't do that. Just keep looking. There's no reason to go nuclear. It could still be fixed.

 

thanks for the heads up everyone, I'm not ready for a hail marry pass just yet, so I'll hold off on the heat gun. I'll keep digging at it and see if I can find the cause... hmmmm....