Zed Blade - Bad Repair or Partial Boot?

ShootTheCore

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I just acquired this Zed Blade cartridge. The game passes the UniBios CRC check, and the game plays fine. However, the music for the last stage (0x072B) is just straight static.

Opening the cartridge up, the majority of the chips are mask roms, but you can see that S1, M1 and P1 are EEPROMs. There is an SNK sticker on them which hints at a factory repair. I didn't take pictures of the backs of the boards, but they are both cleanly wave soldered with no signs of tampering.

What are my options here? Can the S1 EEPROM be reprogrammed to fix that static track? Should I try to scavenge the correct Mask ROMs from a damaged board?

IMG_8336.jpgIMG_8339.jpg
 

ShootTheCore

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Upon further consideration, I suppose that the EEPROMs could be all factory originals, but the S1 EEPROM factory-original programming could be degraded given the passage of time. Hmmm ... again what are my options here? Is it worthwhile to try to reprogram the EEPROM?
 

Fox1

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If an EPROM degrades then it will not match CRC, it would a different CRC number... so it's probably something else.

Also might be wise to put those scans on Mvs scans..very interesting.
 
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ShootTheCore

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If an EPROM degrades then it will not match CRC, it would a different CRC number... so it's probably something else.

Also might be wise to put those scans on Mvs scans..very interesting.

I was surprised that it passed the CRC check with the garbled sound track. Does the CRC check cover the sound and art banks as well, or only the programming code?

I fired up my 120 in 1 multicart to double check Zed Blade on the same MVS. The multicart flunks the CRC check but the sound track is fine. Irony....
 

Fox1

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I was surprised that it passed the CRC check with the garbled sound track. Does the CRC check cover the sound and art banks as well, or only the programming code?

I fired up my 120 in 1 multicart to double check Zed Blade on the same MVS. The multicart flunks the CRC check but the sound track is fine. Irony....

A garbled soundtrack could, mean like Tyranix said a bad pcm chip...if you really want to be sure..desolder the sound eprom and check it via known mame dumps.
 

HeavyMachineGoob

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Upon further consideration, I suppose that the EEPROMs could be all factory originals, but the S1 EEPROM factory-original programming could be degraded given the passage of time. Hmmm ... again what are my options here? Is it worthwhile to try to reprogram the EEPROM?

The S1 ROM contains fix layer graphics, such as life bars and credit counters. What you are probably looking for are the V ROMs on the PROG board, those contain YM2610 code, which is all the sound. There's also the M1 ROM which contains Z80 code, basically it runs code that dictates the YM2610's job.
 

ShootTheCore

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The S1 ROM contains fix layer graphics, such as life bars and credit counters. What you are probably looking for are the V ROMs on the PROG board, those contain YM2610 code, which is all the sound. There's also the M1 ROM which contains Z80 code, basically it runs code that dictates the YM2610's job.

Great clarification on which ROMs hold which data. Somehow I got it stuck in my head that S-ROMs = Sound ROMS.

The V-Roms here are Mask ROMs, so I'm presuming that they're okay. The M1 ROM is an EEPROM however, so perhaps that's the one that has decayed.

Seems like the best solution would be to desolder the EEPROMs and compare them against good dumps. Frankly I'd prefer to re-flash all three EEPROMs just to make sure they're fresh. I don't have the soldering expertise or flashing equipment necessary however.

Can the EEPROMs be re-flashed without removing the SNK window stickers? I'd like to keep the cartridge boards authentic if possible.
 
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DNSDies

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Can the EEPROMs be re-flashed without removing the SNK window stickers? I'd like to keep the cartridge boards authentic if possible.

Depends.
Is there a notable depression under the sticker, as if there is a small window under it?
If so, that's actually an EPROM, and it has a quartz window in it for erasure via UV light.

If you want to preserve the SNK stickers, you can use steam or a heat gun to melt the adhesive and gently lift it off from the EPROM with some tweezers.

Also, if you need EPROM erasing/programing, and live in California, I'd be happy to offer my services for free if you pay for the shipping to and from.

The erasure takes about 35-40 minutes (I can erase 6 at a time), and programming them will take about 5 minutes each.

I don't need the whole cart, just the EPROM chips and the rom dumps you want on them.
 

Xian Xi

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If it was a PCM chip problem then all of the music would be garbled, right? Only the music for the last level is garbled ...

No, it would depend on how far gone the PCM is. Sometimes it just sounds like a 56k modem trying to connect to AOL.

Edit: BTW, can you snap pics of the backside of the PROG board? I just want to see if there's anything on the back of concern.
 
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HeavyMachineGoob

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Great clarification on which ROMs hold which data. Somehow I got it stuck in my head that S-ROMs = Sound ROMS.

The V-Roms here are Mask ROMs, so I'm presuming that they're okay. The M1 ROM is an EEPROM however, so perhaps that's the one that has decayed.

Seems like the best solution would be to desolder the EEPROMs and compare them against good dumps. Frankly I'd prefer to re-flash all three EEPROMs just to make sure they're fresh. I don't have the soldering expertise or flashing equipment necessary however.

Can the EEPROMs be re-flashed without removing the SNK window stickers? I'd like to keep the cartridge boards authentic if possible.

Actually, Mask ROMs have been known to become faulty or outright die, depending on circumstances. I own a copy of MegaMan 2 for NES that developed a bad PRG ROM, it would always crash in specific places. A new EPROM fixed that.

Also, EPROMs can retain their data for 40+ years without data loss. What you should probably do is cover the EPROMs with foil stickers or electrical tape, helps reduce stray UV. Mind you, even an hour out in the sun doesn't do much for most EPROMs, you need a strong UV lamp to nuke EPROMs fully.

You have to remove the stickers covering the windows to erase EPROMs.

Now as for what would be broken on your cart, if the M1 ROM was bad in a specific place then the audio would go completely silent. Usually when garbage is being played, it's a V ROM issue.

Unfortunately, what you should probably do is have each V ROM desoldered, put into a EPROM programmer and compared with a correct MAME dump, to determine which V ROM is reading wrong, then replace it with an EPROM.
 

Xian Xi

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Actually, Mask ROMs have been known to become faulty or outright die, depending on circumstances.

For the Neo it is 90% of the time the Toshiba Mask Roms, the Sharp ones I've never seen go bad from things internal, only from rust moving in from the leg.
 

HeavyMachineGoob

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Really disappointing too, I like Toshiba's parts. As far as I'm concerned, the worst IC manufacturer in general is Fujitsu, their logic chips are basically ticking time bombs. I'm not sure if their Mask ROMs are any better yet.
 

DNSDies

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As far as I'm concerned, the worst IC manufacturer in general is Fujitsu

Their flash chips are pretty terrible too.
I've had a few 29F033C chips suddenly lost the ability to write anything except 00 or FF to them.
 

ShootTheCore

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OK, I cracked open the cartridge again and took pictures of the backs of the boards.

First off, I may have located the problem. Pin 23 on V2 looks like it may have rusted through or been damaged somehow. See closeup in pics below.

Also the upper-right back corner of the CHAR board looks like it has some scuffs along the circuitry. No ROMs are located there, but there is a possible broken circuit there if that matters. See closeup in pics below.

I also confirmed the CRC pass in Universe BIOS and that the 0x072B track still sounds like modem static. It follows the beat of the track - just alternates between silence and static, sometimes passing to the left and right speakers where the proper track would.

I did confirm that the three ROMs with SNK stickers are all indeed programmable EPROMs. You can feel the window underneath the SNK stickers.

Thoughts?

IMG_8348.jpg

IMG_8363.jpg

IMG_8362.jpg

IMG_8350.jpg

IMG_8343.jpg
 

DNSDies

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That is DEFINITELY some corrosion you've got going on there.
Break out your multimeter and do continuity tests on the points surrounding the spots of corrosion on the trace, to ensure it didn't eat through them.
You'll also want to remove that stuff ASAP before it gets under the solder mask and makes things worse.

Get some vinegar and a toothbrush and gently brush the corroded spots to try and pick up any rust or oxidation. If it works, clean the vinegar off (it's a weak acid, don't want to leave it on long term) with some iso alcohol (90% or more) and tin the exposed areas with solder and use some kynar wire to bridge any breaks in the traces.
You may need to use a fiberglass pen to remove the more stubborn spots, or expose more of the copper of the traces for a repair, but be VERY CAREFUL (practice on something else first)

Once you've confirmed everything has continuity, test it again and if it works, consider applying some brush-on solder mask over the repair spots to protect them long-term.
Good luck man.

I've gone ahead and circled some points to test for continuity. "D" I'm assuming goes to a cart-edge pin.

UZ6T9q7.jpg

hFwfJq3.jpg
 
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ShootTheCore

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That is a huge help DNSDies - Thank you very much.

I'll work on it later this week and report back.
 

Atro

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I'd do it for free, but the postage costs would be killer for you.
I personally am not ok with the use of vinegar ( that's just me ). I'd go with Isopropanol alcohool to clean it. Making a small cut and bridge the trace is also an option.
What DNSDies said is pretty much accurate.
 

DNSDies

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The idea with cleaning corroded board traces is you start with a weak solvent and work your way down to less friendly acids.

Iso alcohol IS a good start, and it is highly unlikely to damage anything (it WILL make the board sticky if the manufacturer didn't clean the flux off though).

So, yeah, start with iso alch like atro says. If it works, you're golden. If not, try vinegar. Just be mindful that the more acidic the solution, the more collateral damage potential it has to do to the board.

Use a cotton swab to minimize the area of exposure.

My usual hierarchy of acidic substances is: Water, Iso Alcohol, vinegar, and naval jelly for the REALLY horrible stuff (this stuff is basically jellied acid, USE WITH CAUTION)

Also, if worst comes to worse, do what Atro says and just cut the traces fully and bridge them with wire.
 

ShootTheCore

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I also have some Deoxit D5 Contact Cleaner, and some Deoxit Gold G5 Conditioner. Would those be better to use than Iso Alcohol?
 

DNSDies

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I've never had much luck with "contact cleaners" in removing rust and corrosion, but it couldn't hurt to try.

I looked it up, and it's like 75% mineral spirits, so it's at the very least safe to try.

Also, you might try giving this a read:
http://www.crazykong.com/tech/CleaningPCBsFAQ.txt

Lots of useful info.
 

RabbitTroop

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I've never had much luck with "contact cleaners" in removing rust and corrosion, but it couldn't hurt to try.

I looked it up, and it's like 75% mineral spirits, so it's at the very least safe to try.

Also, you might try giving this a read:
http://www.crazykong.com/tech/CleaningPCBsFAQ.txt

Lots of useful info.

D5 isn't a contact cleaner, it's for removing corrosion, though those parts look like they've moved from corrosion into outright rust. Not sure if DeOxit will remove everything, but it's a start. If those traces are bad, just solder in some wire to reconnect them, or if that looks too ghetto, might be time to look for a new donor cart that will be a good swap. There are plenty of bad boots on good boards that can be salvaged if need be.
 

Xian Xi

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I also have some Deoxit D5 Contact Cleaner, and some Deoxit Gold G5 Conditioner. Would those be better to use than Iso Alcohol?

Alcohol is only good for cuts not for cleaning electronics. I can't believe people still recommend it. You can save money by using spit instead of alcohol and get the same effect. Alcohol is only good for cleaning off residue like flux but not for cleaning contacts. I've Deoxit for a long time now and nothing comes close when it comes to cleaning PCB connectors. In fact when I troubleshoot AES and MVS systems that people send to me, about 85% of the time it's just a dirty slot because they use alcohol and I then clean the slots with Deoxit and the problem is gone. Happens way too often.
 

Xian Xi

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With the rust I'd use a fiberglass pen to get it off then use some nail polish(non-metallic) once it's reconnected to protect it.
 
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