Neo Geo MV1FZ sound issues

PCB problems and fixes
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keropi
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Neo Geo MV1FZ sound issues

Post by keropi »

Hiya!

I noticed a problem with a MV1FZ + Metal Slug combo I have , it seems that at certain parts of the game the sound cuts off (not completely you just hear half the stuff) and returns after a while - this always happens at the same places... :eh:
For example:

- when you reach this area in the first stage and blow the barrels the sound cuts off, like half the channels are muted or have very low volume:

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then you get the tank and it become more silent:

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after you reach the river and kill the 1st enemy tank sound returns as normal:

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Sometimes I get a Z80 error on boot but after a power-cycle it goes away... I cleaned the contacts of the cartridge and jamma connection and it seems this cured that. But not the sound issues.
The board is in great condition, no scratches, battery spill or other damage visible

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The original installed caps are TK brand - AFAIK they are really cheap ones. Is this a case of a sound recap? Or maybe something worse like a semi-dead Z80 or YM2610 ? What should I look for?

TIA for any help/info!
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Re: Neo Geo MV1FZ sound issues

Post by pulstar »

The fact that you are getting an intermittent Z80 error means something else could be on its way out, possible the sm1 ram. Best thing to do is to burn a diagnostics rom and a Z80 testing cart from here http://smkdan.eludevisibility.org/neo/diag/ and it should point you in the right direction.
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Re: Neo Geo MV1FZ sound issues

Post by keropi »

thanks for that, I see I also need a cartridge and replace a rom in it with the M1 rom from the diagnostics bios. I hope Metal Slug or Samurai Shodown are suitable , they are the only MVS games I have atm
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Re: Neo Geo MV1FZ sound issues

Post by pulstar »

It might be worth seeing if someone has one you can borrow instead of making a new cart for one board.

Just remember if you do it, the CHA board is the only one used in the Z80 testing and it needs a NEO-ZMC on the board. Looking at MVS-Scans both SamSho and Metal Slug should have the NEO-ZMC IC.
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Re: Neo Geo MV1FZ sound issues

Post by keropi »

oh great, didn't have the chance yet to look at my carts , nice to see that they are both suitable. I'll just socket the rom in question and have the option to either use the pcb for test or game, hopefully there is space to do that :)
thanks again!
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Re: Neo Geo MV1FZ sound issues

Post by keropi »

had a look at my Samurai Shodown cart:

Image

NEO-ZMC is there and M1 is a 32pin device... turns out that the TC531001CP-12 is a "128K word X 8bit" device, so one can use a 27SF010 (128K X8) or 27SF020 (256K X8) for it , right? I was under the impression I needed another 27C1024 eprom for this... got plenty of 27SF020s here, I think there is enough space to install a socket for the M1 rom :)
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Re: Neo Geo MV1FZ sound issues

Post by pulstar »

That's right. I used a 27c010 in mine. If you use the 020 remember to double the m1.bin image. You'll need a 27c1024 for the diagnostics bios to put onto the motherboard before you can use this cart, though.
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Re: Neo Geo MV1FZ sound issues

Post by keropi »

awesome thanks for the confirmation :)
I can get some OTP AT27C1024s : http://www.tme.eu/en/details/at27c1024- ... its/atmel/ , luckily the bios is already in a socket on the motherboard
I am debating weather to destroy the original M1 rom so I can desolder it easily and safe (cut it's legs and then burn the game's data to an eeprom) or try to remove it without killing it... :problem:
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Re: Neo Geo MV1FZ sound issues

Post by keropi »

Thought I post a couple of pics just in case anyone (like me) does not want to make a dedicated Diagnostics CHA board and rather have the M1 rom socketed for easy swap. It can be done but it needs a little filing :lol:

First of all you need to remove the M1 rom and install a socket , make sure the socket sits completely flat on the pcb , every 0.1mm counts. The original mask rom is very easily removed , kinda surprised me as I was expecting hard-to-melt solder tbh, with a little wick the job is a piece of cake. (that black stuff near the DIP holes is not burned pcb, just residue from the flux in the wick - took the picture before cleaning it :roll: )

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Now for the filling part:

- you need to shorten the legs on the original mask rom so that it goes all the way in the socket , just trim 1~1.5mm of them and it will be fine (not more!)
- you need to file any pins on the PROGGSC upper board that might conflict with the extra height of the M1 rom + socket , with my Samurai Showdown cart I have to shorten the pins inside the red rectangular:

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Just snip the pin part above the solder, file a little to flatten it and re-apply a little solder to make sure all is well.
After that the original M1 mask rom fits nicely inside the cart and you can close it as normal. Overall a very easy job.

I am still waiting for the 27C1024 eprom to arrive so expect some more posting once it does and I burn the BIOS in it. 8-)
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Re: Neo Geo MV1FZ sound issues

Post by leonardoliveira »

I never, EVER heard of one having to trim legs from DIP ICs to make them fit on a socket.
DIP sockets are designed to take in chips with their original legs uncut. Imagine how awkward it would be if we had to. There would be DIP chip leg trimming tools then...

:eh:

Edit: One thing that might be of interest is that you're best sanding the excess of solder from the pins as that will latch on the socket when the chip is inserted and has potential to then "attach" to the socket contacts. That would cause the socket contacts to bend outwards when the chip is pulled. Make sure you leave almost no tin on it's pins.

Or you can simply use higher quality sockets with round pin holes which won't give you headaches about pins with tin residue in them...

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Re: Neo Geo MV1FZ sound issues

Post by keropi »

The point of trimming 1mm of the mask rom legs is to gain height - maybe I did not make it clear above.
If you do not trim the legs a little then the mask rom sits too high in the socket (as the legs reach the bottom and there is ~1mm empty space between the socket and the inserted masrom) and you cannot close the cartridge easily like that. Trimming said 1mm then the mask rom goes ALL the way down to the socket (leaves no space between the socket and the maskrom) and it helps with the height restriction that exists.

Ofcourse you don't have to trim anything under normal situations - that would be crazy :lol:
I will take some pics later and you can see why , it's a very close fit to have a socketed rom in the CHA board and still be able to assemble the cartridge without forcing anything - at least that is the case of my Samurai Shodown cart. Snipping 1mm of maskrom legs is a small price to pay for the cart to close normally with a socket :awe:

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There is no need to sand excess solder from the pins of any IC ever - it's way better to use solder wick for that. That's what I always use when it's needed.
The round-hole sockets are not correct ones for ICs that have flat legs like the eprom in question. You can use them , they will work but it's just not the correct socket for this .
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Re: Neo Geo MV1FZ sound issues

Post by keropi »

this is why I trimmed the mask rom legs, this is what allows the cart to close without any force , tha mask rom need to go in the socket all the way.

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Re: Neo Geo MV1FZ sound issues

Post by invzim »

Did the debug cart tell you anything useful? Got a mute mv1a myself that I haven't been able to resurrect.
I make and sell cool Arcade stuff, check out https://irkenlabs.com/ - In The Name of Science!
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Re: Neo Geo MV1FZ sound issues

Post by keropi »

I am still waiting for the 27C1024 to arrive, it appears I will receive it tomorrow... I hope it does say something usefull :D
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Re: Neo Geo MV1FZ sound issues

Post by keropi »

Did the test and got this:

Z80 DEAD / ERRORED / COMM. ISSUE
EXPECTED: 3C
ACTUAL: 4C

Z80 REPORTED ERROR CODE: 0C
Z80<->68k COMM. ERROR (DATA)

Making subsequent tests via power cycle or soft-reset passes all tests with success (even Z80 ones!) - I can only speculate this happens in cold boot when the board was powered off for some time?
I cannot seem to replicated it atm, I saw the error once and then after ~30 resets I don't get it anymore.
Board is really clean and scratch-free.

With the board connected I put back the original BIOS and Metal Slug. Powered on and was greeted with a Z80 error. Did a quick power-cycle , Z80 error was gone but had the same sound issues.

Any suggestions on how to proceed with this?
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Re: Neo Geo MV1FZ sound issues

Post by pulstar »

Because the problem is intermittent it seems to suggest something like cracked or cold solder joints,. Check the sound circuit for cold solder joints and see if that gets rid of the problem. I would assume, though, that when the problem goes your sound should come back, but it sounds like it doesn't. This could also be a capacitor problem as well as the problem in the sound circuit.
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Re: Neo Geo MV1FZ sound issues

Post by keropi »

Thanks for the suggestions!
I'll start with a reflow then and a recap and see where that takes me. I'll update when I do these things. :)
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Re: Neo Geo MV1FZ sound issues

Post by keropi »

Did the recap today, nothing changed: first boot -> z80 error , then afterwards I get the same sound issues... will try reflow tomorrow and see what happens
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Re: Neo Geo MV1FZ sound issues

Post by keropi »

did the reflow today, I still have the same issues , z80 error and missing sfx... I can't replicate the diagnostics bios error today, everything checks out ok :wtf:
I'll post on neogeo forum , maybe someone there have seen this problem before
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Re: Neo Geo MV1FZ sound issues

Post by pulstar »

Strange after the recap that there's still nothing on the sound. If the Diag Cart completes its tests fine there has to be something on the output side (op-amp, power amp etc). There is still a possibility that the Z80 is going out, but after the reflow it seems harder to replicate (or it hasn't replicated at the moment?) and so it seems that was the problem with the intermittent Z80 error.
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