2 Slot not displaying character sprites

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Warpedflash

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My consolized 2 slot no longer displays all sprites on screen.

The Neo geo logo does not appear on boot up (the text under it does however)
If I attempt to start up any games there are big chunks of the game missing and having no characters displayed in a fighting game cranks up the difficulty rather a lot...

I don't know where to start diagnosing this... I don't have a scope (and honestly don't know how to use one) but am quite happy removing surface mount chips and doing normal mod/repair work so if anyone could point me in the right direction I believe I would be able to fix it.

Any help is appreciated!
 
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Pingu

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Start by cleaning slot and carts, if problem persists it's probably some bad ram or other faulty component that others can give you a better clue about.
 
BIG BEAR

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It's most likely the NEO ZMC2 or one of the NEO-257 chips (mainly the two near the ZMC2) that will need solder re-flow or replacing.
BB
 
Last edited:
Xian Xi

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BIG BEAR said:
It's most likely the NEO ZMC2 or one of the NEO-257 chips (mainly the two near the ZMC2) that will need solder re-flow or replacing.
BB
Click to expand...

I agree. If the sprites are gone completely then check those out.
 
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Warpedflash

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Thanks for the suggestions guys. I will have a look into the ZMC2 and NEO-257 chips, hopefully its just a reflow that's needed.
 
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Warpedflash

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Well I reflowed all 3 chips and now just get a light band at the top of the screen :-( I assume I had my iron too hot and blew the chips? Any way of testing this?
Also if I have knackered them us the only way to get replacements to use a donor board?
 
bustedstr8

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Thermal damage is unlikely....unless you left your iron on the board to make a sammich.
Solder bridges are way more common when doing QFPs. Check them with a loupe and meter.
 
BIG BEAR

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I don't know if you did this BUT you should have re-flowed one chip at a time,not all at once. You did not damage any of the chips,you most likely bridged the legs of the chips with solder as bustedstr8 mentioned.
What you want to do right now is focus on your ZMC2...make sure that chip is making an absolute GOOD connection..because it has the most legs and is likely the cause of your solder bridges....make sure there's no flux residue messiness going on at the base of the legs as well....rubbing alcohol & a Q-tip should clean that up.you may have to flake some of that flux away as well..

BB
 
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Warpedflash

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BIG BEAR said:
I don't know if you did this BUT you should have re-flowed one chip at a time,not all at once. You did not damage any of the chips,you most likely bridged the legs of the chips with solder as bustedstr8 mentioned.
What you want to do right now is focus on your ZMC2...make sure that chip is making an absolute GOOD connection..because it has the most legs and is likely the cause of your solder bridges....make sure there's no flux residue messiness going on at the base of the legs as well....rubbing alcohol & a Q-tip should clean that up.you may have to flake some of that flux away as well..

BB
Click to expand...

I know I should have done them one at a time. I don't really know why I did them all at once to be honest...
I will give the board a good clean up and check for bridges although I cant see obvious ones. Thanks for the help!
 
channelmaniac

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Let's step back for a moment. Look at the battery and the traces around it. If the battery has leaked and damaged traces then you'll have disappearing graphics elements. Hell, you'll even have problems with the backup RAM circuitry which could lead to the thing acting totally dead.

Post pics of the area around the battery, NEO-257 chips, NEO-ZMC2, and the backup RAM. One pic should cover it.l
 
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Warpedflash

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channelmaniac said:
Let's step back for a moment. Look at the battery and the traces around it. If the battery has leaked and damaged traces then you'll have disappearing graphics elements. Hell, you'll even have problems with the backup RAM circuitry which could lead to the thing acting totally dead.

Post pics of the area around the battery, NEO-257 chips, NEO-ZMC2, and the backup RAM. One pic should cover it.l
Click to expand...

When this came into my hand a couple of years ago the first thing I did was remove the battery before it go the chance to leak. I will try a get a picture up later this evening.

After cleaning up the board a bit post reflow I get a picture again but it is not a dark image of lots of small garbled squares of color :-/ I have definable done something to this board while attempting the repair as it's gotten worse... I checked the solder joints and they seem to be OK as well
 
channelmaniac

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Sounds like you bridged some traces still or you have a problem in the backup RAM circuit. You need a jeweler's loupe to check for bridges.
 
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Warpedflash

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channelmaniac said:
Looks like there's a chunk of something between pins 3 & 4 on the ZMC2
Click to expand...

There was a bit of blobby solder on leg 4 but it wasn't bridging to leg 3 (my continuity test didn't go off anyway) I removed the blobby bit so it looks neater. Hopefully my loupe should arrive tomorrow so I can get a much closer look
The image on screen looks like this at the moment...
 
Xian Xi

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Why does it look like a fluxless reflow? Use flux, always.
 
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Warpedflash

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Used lots of flu. Just cleaned it up afterwards as bb suggested above.
How would I tell if the chips are clocking?
 
Atro

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Warpedflash said:
The image on screen looks like this at the moment...
Click to expand...

I had a very similiar screen like yours on one of the boards I had here from a local operator.
Turns out the BIOS was faulty and shown a very similar pattern like yours.
Swapped the BIOS and problem solved. It was a 1-Slot tho.
 
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Warpedflash

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Atro said:
I had a very similiar screen like yours on one of the boards I had here from a local operator.
Turns out the BIOS was faulty and shown a very similar pattern like yours.
Swapped the BIOS and problem solved. It was a 1-Slot tho.
Click to expand...

Tried the bios from a one slot I have and there is no difference.
 
bustedstr8

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You'll need a scope or logic probe ($20) to see if the chip is clocking. You could be wasting all your time with the solder work and the chip is stone dead.
 
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Warpedflash

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bustedstr8 said:
You'll need a scope or logic probe ($20) to see if the chip is clocking. You could be wasting all your time with the solder work and the chip is stone dead.
Click to expand...
Sorry or the delayed reply I have been on relative duty and away from this for a couple of days.

Would something like this be suitable? I live in the UK so if this isn't OK could you suggest something that might work. I don't mind spending a bit if It help me learn some of this better anyway.
 
bustedstr8

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Warpedflash said:
Sorry or the delayed reply I have been on relative duty and away from this for a couple of days.

Would something like this be suitable? I live in the UK so if this isn't OK could you suggest something that might work. I don't mind spending a bit if It help me learn some of this better anyway.
Click to expand...

looks good
 
BIG BEAR

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That last photo looks as if you re-flowed solder on the NEO EO or FO and you have a solder bridge going on somewhere which now gives you that black and blocky screen.
The ZMC2 is the culprit for your initial problem. I just re-flowed solder on a 2 slot I have now(between legs 1-24,the side closest to where the battery would be) before I gave it another go over.
BB
 
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