MV2F Garbled crosshatch *FIXED*

knohbody

n00b
Joined
Apr 6, 2012
Posts
16
So, helping out someone with a 2 slot (MV2F). Original issue was a calendar error, apparently due to battery damage. The crystal was replaced before I got to the board.
I cut out the battery, removed the resistor in the charging circuit (470 ohm), and added a battery holder.
There was a corroded 22k ohm resistor near the battery that I replaced. Most of the legs on one side of the HC32 nearest the battery were also corroded, so replaced that as well. Jumped a broken trace from pin 13 on the HC32 to the 22k ohm resistor.
There is also a 10D1 Diode near the battery that is corroded and needs to be replaced. I believe that's part of the charging circuit, but not sure.
Right now it's booting to what looks like a garbled crosshatch screen, with nothing else. I'm unable to get into the work ram test or boot into a game.
So I'm thinking theres still something wrong near the battery, maybe with the crystal.
Here are my logic readings for the 4990 and HC32:
4490:
pin 1 - H pin 14 - H
pin 2 - H pin 13 - H
pin 3 - H pin 12 - H
pin 4 - L pin 11 - L
pin 5 - L pin 10 - L
pin 6 - L pin 9 - H
pin 7 - L pin 8 - L

HC32:
pin 1 - H pin 14 - H
pin 2 - H pin 13 - L
pin 3 - H pin 12 - L
pin 4 - H pin 11 - L
pin 5 - H pin 10 - H
pin 6 - H pin 9 - H
pin 7 - L pin 8 - H

Any suggestions on where to start?
 
Last edited:

channelmaniac

Mr Neo Fix-it
15 Year Member
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Nov 29, 2005
Posts
4,275
Post a pic... and check the traces going from the NEO-ZMC2 chip down towards the front of the board.

You should be able to flip all the DIP switches on and get to the Work RAM Test. If you can't then check the DIP switches and the traces for them.
 

knohbody

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Apr 6, 2012
Posts
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ImageUploadedByTapatalk1342871869.697735.jpg
ImageUploadedByTapatalk1342871912.101135.jpgImageUploadedByTapatalk1342871927.731832.jpg
ImageUploadedByTapatalk1342871962.356643.jpgImageUploadedByTapatalk1342871993.336415.jpg

Dip switches ohm out ok at the solder joints and traces for them have good continuity until they end under the neo-f0 chip, at which point I'm not sure where to check.

The neo zmc2 chip has corrosion on the 1-24 pin side. I will check for continuity and traces on that when I get back from work today.

As a side note, the ym2610 is fairly warm to the touch when it's on.
 

channelmaniac

Mr Neo Fix-it
15 Year Member
Joined
Nov 29, 2005
Posts
4,275
That's not a garbled crosshatch. That's just dead.

Check pin 20 and 22 for signals. They shouldn't be stuck high.

Two to 1 says you missed a bad trace or plated through hole near the battery backup section & the HC32.
 

Xian Xi

JammaNationX,
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Dec 1, 2005
Posts
27,748
Clean up the repair work, too. That jumper wire really doesn't need to be that long if the points are directly across from one another.
 

Xian Xi

JammaNationX,
15 Year Member
Joined
Dec 1, 2005
Posts
27,748
That's not a garbled crosshatch. That's just dead.

Check pin 20 and 22 for signals. They shouldn't be stuck high.

Two to 1 says you missed a bad trace or plated through hole near the battery backup section & the HC32.

Hey RJ,

What do you use to clean off pins that you can't solder to due to corrosion?
 

knohbody

n00b
Joined
Apr 6, 2012
Posts
16
That's not a garbled crosshatch. That's just dead.

Check pin 20 and 22 for signals. They shouldn't be stuck high.

Two to 1 says you missed a bad trace or plated through hole near the battery backup section & the HC32.

Likely this is the case. I'm still a rank amateur at this stuff. I took the hc32 back off (and destroyed it in the process) and found one of the thru holes was bad. Not sure if I messed it up when I took the chip off or if I missed it the first time.
Now I need to get a new chip. I'll prolly also socket it, just in case.
If it proves to be beyond my skill, I may hit you up to see how much you'd charge to fix it. I need to pick up some cap kits for my four slots any way.

Thanks to both of you for the advice. It'll prolly be a few days before I can pick up a new chip.
 

knohbody

n00b
Joined
Apr 6, 2012
Posts
16
Ok, finally had time to work on this today. I repaired two traces on the HC32 (That I probably damaged), replaced the HC32 chip, replaced the corroded 1d10 diode with a 1n4003 diode from radio shack.
All of this to get back to where I was: Calendar error on boot.
Put all the dip switches down, got work ram test screen, putting them back up, it didn't continue to boot.
Found this thread where MKL kindly posted the connections to the 4990 chip. Traced those and found pin 10 of the 4990 chip going to neo-f0 pin 32 had a damaged trace. Jumped this with some wire, and it works.
There are some lines in the graphics, so i'll have to check into that, maybe the game.
 

channelmaniac

Mr Neo Fix-it
15 Year Member
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Nov 29, 2005
Posts
4,275
Could be corroded traces around or under those NEO-257 chips... Battery damage can be a bitch!

And James, use a fiberglass pen to clean 'em. If you can't get the pins clean enough to take solder then you have to scrape them carefully with a hobby knife.
 

knohbody

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Apr 6, 2012
Posts
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Vertical lines were caused by the cart not seating properly. Other carts worked fine, when I tried the problem cart again it came up fine.
 
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