MVH MV4 Backup Ram FF40 Error, replaced backup ram, no difference....

DCrosby

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So I had a party over labor day, and the machine was sitting in Attract mode, when I started hearing the Coin Counter fire, at first slowly and then quicker. I shut the machine down. Let it cool and booted it again. Booted fine, and then the coin counter started counting, I checked the coin mech and disconnected everything on the coin mechs, looking for a short. None to be found, coin counter continued to count. So I shut it down again and disconnected the coin counter, figuring I'd check it later. The machine booted and ran fine. For another hour or so, when I had to shut it down to power a vaccuum for getting the patio ready, and when I re-started the 4 Slot, I got a backup memory error. At first it wasn't FF40 but I couldn't tell you what the value was. I then shut it down, and turned it back on, and now it's consistant FF40, and I have Unibios, so I was able to run the party on single slot AES mode, and figured I'd check the error later. Well later is now, and I looked at it, "Ok it's the backup ram, the lower 2 chips on the board"
I ordered the replacements on Digikey, de-soldered the old ones, and then replaced them with the new ones. No dice, same error FF40. So I started searching, and found the HC32 had to be connected to pins 16, from two of it's(HC32's) Pins. Ok Check it is... also checked pin 27 to the CPU check has continuity...

So now I'm at a loss, should I start ordering another HC32? And maybe the original memory chips weren't bad...

I'm thinking of connecting a logic probe up to the HC32 and the memory's Pin 16 to see if I see activity... but... I'm just stabbing in the dark here.
 

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maki

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most of the time its rotten traces, not defective ICs

grab the latest DIAG BIOS and run it, it would give you better information about the problem
 

hatmoose

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I had an almost identical probem on my "haunted MF4-FT2 from hell" over here
https://www.neo-geo.com/forums/inde...hdog-even-with-neogeo-diagnostic-bios.267802/

If you've replaced the RAM chips and are getting the exact same problem then chances are it's not the RAM.

It could be the HC32, but infinitely more likely to be rotten traces in or out of the ram. @maki was kind enough to post the ram pinout in that thread I linked above. Visual inspection is pointless - normally the spot where the traces fail is right where the via joins the trace - all of the ones I've repaired have been invisible even under a microscope.

But yeah, with that pinout and a multimeter you'll know if it's a bad trace in no time
 

DCrosby

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So when I checked continuity on everything everything checks cpu to Main and backup ram, except for...

Lower Backup Ram:

20_____74HC32 (13) located at D10
-------> 22_____PRO-C0 (16)
27_____74HC32 (8) located at D10


22 ---> Pro-C0 (16), I checked the via as far as I could before it goes under that cardboard foam stuff, I'm somewhat concerned In if I need to take that off, I'd do more damage, and it's not guaranteed that the traces I need to follow will come off cleanly... most likely not...
So should I just run a Kynar wire between 16 or one of the via's that works, and the pin (22)?

I'm thinking I may just tac on a wire and try it, if that fixes it, I'll have to decide on how to proceed.
 

DCrosby

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Yeah tac'd the wire on, and still same backup ram FF40 error...
I need to find my Diagnostic Bios.. maybe it'll give me more info...
 

maki

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if you soak the foam in IPA, it will be easier to remove it

the DIAG bios would be helpful IMO, usually it has direct hints at what signals are missing, which often can be directly translated into traces ;)
 

DCrosby

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So found a chip I could burn the diag bios to, and ran it, said "BRAM Dead Output (LOWER)" Which I kind of already knew based on the FF40 Error...
 

BIG BEAR

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What's the deal with your continuity to the HC32? Are you getting continuity now at the two points you listed?
If not,you need to.
BB
 

DCrosby

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What's the deal with your continuity to the HC32? Are you getting continuity now at the two points you listed?
If not,you need to.
BB
The two points always had continuety, it was the -------> 22_____PRO-C0 (16) that didn't, but it doesn't seem to matter, if I have the tac'd on Kayar wire in there or not... Error is the same
 

DCrosby

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I also purchased another MV4 Board, it has audio issues, with a re-capped sound section, so I suspect the YM2610, what I think is between the two boards, I should be able to do a side by side (continuety) comparison between the Backup Ram / CPU, since the one with the sound issues passed the Diagnostic with flying colors, just sounds static-y... I hope to come away with a Primary and a Backup board.
 

DCrosby

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No, it was next on my list, but I don't know if I have to use a salvage board or if I can still find those...
And how often do those let go?
 

maki

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HC32 are very common standard logic ICs, cheap too, doesn't hurt to swap it, same problem -> most likely interrupted traces

for the board without sound, can you check if the digital part is working?
 

DCrosby

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Yeah I've seen that video before, it's super helpful and has helped me fix several MVS boards with bad Yamaha Chips, it's why I purchased that one, because I feel really comfortable diagnosing and fixing the sound part.

I tried to do a search last night on HC32 Neo Geo to get a link to Digikey or someplace to get the chip type/model and had no luck, maybe I need to get out the magnifying glass and find it on the case/package.
 

maki

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I tried to do a search last night on HC32 Neo Geo to get a link to Digikey or someplace to get the chip type/model and had no luck, maybe I need to get out the magnifying glass and find it on the case/package.
I used ST M74HC32B1 from ebay I got for cheap, they work just fine
 

DCrosby

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I have the board I purchased with the audio issue, just needed a YM2610 replacement, I had a socket, so I soldered that in, added a new 2610 and it worked like a charm audio issues disappeared... so I'm putting the HC32 replacemnt on hold, until I get the new HC's and can get some sockets ordered, I'll update this thread when that happens, for now I have a fully functional 4 slot board, and I'm good to put it into my little arcade... Thanks for the assist!
 

BIG BEAR

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I have the board I purchased with the audio issue, just needed a YM2610 replacement, I had a socket, so I soldered that in, added a new 2610 and it worked like a charm audio issues disappeared... so I'm putting the HC32 replacemnt on hold, until I get the new HC's and can get some sockets ordered, I'll update this thread when that happens, for now I have a fully functional 4 slot board, and I'm good to put it into my little arcade... Thanks for the assist!
Oh..you made out with no track repair involved...congrats with that one!
BB
 

DCrosby

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Sockets came in, but no new HC32's yet, if I don't see them soon I'll pillage from one of the parts boards I have...
 

DCrosby

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Great, I ran the board for 2 Days, and now I have a Z80 Error, I have a replacement, but I wonder what the underlying issue is or are all of these boards just suicideing due to age?
 

maki

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Great, I ran the board for 2 Days, and now I have a Z80 Error, I have a replacement, but I wonder what the underlying issue is or are all of these boards just suicideing due to age?
Z80 Error as reported by the stock BIOS means that there is a fault in the digital part of the audio circuit.

Could be the Z80, the SRAM for the Z80, the YM2610, the NEO-C1 (does the relaying d the SD* signal lines between the 68k and the Z80), after that I'd check the NEO-257s.

Using the Diag BIOS can give you better error messages.
 

ack

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I would suggest you clean your carts and cart slots before assuming the Z80 error is a fault with the hardware.
 

DCrosby

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I let it cool down, overnight and turned it back on, and Z80 is not an issue and it's running Unibios 4.0
It kept freezing on Last Resort... for some reason, and it took like 4-6h to do it... I swapped out for Neo Turf Masters, and when I went into the soft Dip you couldn't read the title... it was all garbled... I cleaned the cart, and swapped slots, from 2 to 1, and it didn't change, also when I ran Neo Turf Masters, It kept spwinging and saying it was too weak, I could change the angle of the shot, and try and strike the ball earlier, but not later than the middle of the strength bar... very odd... I swapped it out for Fatal Fury, and it's been running all afternoon without crashing or glitching... so maybe I do need to clean the contacts... but I'd think it would stay with the slots if that was the issue... :/ The Gremlins on these things are crazy....
 

ack

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I swapped out for Neo Turf Masters, and when I went into the soft Dip you couldn't read the title... it was all garbled

This is likely a unibios thing. If you insert a new cart and go directly to soft dips you will get the garbled text. You need to boot into the game once so it can initialize its soft dip data.

I would double check the voltage on your 5V rail while the board is powered on running a game.
 
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