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[Repair Log] NeoGeo MVS

TylerDurden67

TylerDurden67

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Hello everyone,

I will identify here all the repair log on MVS I could help.
I will try to be as instructive distraillant concerning compensation for slots.
Enjoy reading !



Today I received a new kid in the family


MV2FS that tells me a good


Fairly standard, I would say

Anyway after having opened the beast, I see that the battery is still in place, and slightly oxidized.


Having had bad memories with a stack on my MV6, I decided to remove it immediately and replace it with a support for a CR2032 button battery.
Finally, once soldered, it was not so dramatic as that, but better to be proactive


Install stand below the map, it's safer if spilled, and this avoids any disassemble to change the battery.
Do not be mistaken about the meaning, between + and -.


Last thing to perform very important,
you MUST desoldering resistance of 470ohms, otherwise the slot will recharge a battery that is not planned for!




This is in place, we talk no more, one less thing to worry about.
Returning to error


The slot indicates 55D5, D5 means that this is the backup lower ram is at issue
(here right above the unibios, a 43256, already changed in this photo)



I checked that the data going well between the 74HC32 that manages and each ram.
The lines are ok so I change the boot ram and it's alive!


and that's yucky: oo:
(I do not mean the choice of strategic game to test)

Test with another


In short, we notice that the background work roughly the texts are ok, but some sprites are streaked.
We can limit searches, this type of display are managed by NEO-257 which are coupled to NEO-ZMC2.

By testing the lines of the NEO-ZMC2 a logic probe, certain outputs are HS.

I decided to change the



and new test ...




20150523084250-TylerDurden67-tumblr-mnhj9nzfFg1qcimv5o1-250.gif





followed by a beautiful


facepalm.jpg


Like a jerk, I forgot to reset backup ram.
Via the unibios, it's pretty simple, we need to start free slot play, press repeatedly managed to start and it will offer to do so.
Otherwise, on a slot with classic bios, put all the DIP switch to 1 and on.


Retest the blow and, as my colleague Portuguese "c'est ca it's good!"







Small test on the second slot and ...
tada !!!!






double_facepalm.png



Yeah, I subscribe to the second shit ...

After test, one of the NEO-257 got bad outputs.
Only problem, requires a multislot organ donor, except I do not have one.
I can graft it a 74HC257 in parallel to operate at 100%, but this type of hack yucky, that does not connect me.


Finally, I will stop there, waiting for a NEO-257.It will make a beautiful MV-1 Slot luxury and bulky!
 
good stuff. I've ran into the exact same problems with a 2 slot bought as broken. Fortunately I only bought the thing for its memory card reader.
 
My 2 slot mvs recently started getting lines on the sprites. I hope it doesn't need advance repair on it....
 
Sometime those MVS slot-2 do strange things depending on wich game you play after wich other.
Metal Slug 4 is a reknown bitch for that !!
Those lines happen from time to time for me and very rarely I can make them go without trying
another game before the game that's giving me trouble. I thought it was a 100% mechanical slot problem at first
but it seems not in end.
I also have regular issues when booting a legit Sengoku 3 on my slot 2.
If I load it first on the slot 1 it goes 9 times out of 10 on a checksum and then it can work on both.
 
Large Kro said:
Sometime those MVS slot-2 do strange things depending on wich game you play after wich other.
Metal Slug 4 is a reknown bitch for that !!
Those lines happen from time to time for me and very rarely I can make them go without trying
another game before the game that's giving me trouble. I thought it was a 100% mechanical slot problem at first
but it seems not in end.
I also have regular issues when booting a legit Sengoku 3 on my slot 2.
If I load it first on the slot 1 it goes 9 times out of 10 on a checksum and then it can work on both.
Click to expand...
Metal Slug 4 requires PCB shaving as it was manufactured too wide and causes the PCBs to warp when inserted into the cart slot causing a bad connection. If your's is already shaved then it's most likely a dirty slot with all the symptoms you describe.
 
Honestly I never disassemble the cart so I never noticed that. I should have a look at it since it can cause damages with time too, bad solders. What's funny and it seems you know your stuff well, is that the process I found works each time and has nothing to do with the real issue :D
 
Just mentioning, not related to the OP post, just related to the repair he had to do first. The first thing that blows when overvoltaging the boards are the RAM chips. I believe that is why most times we have to repair boards it's the RAMs that went bad...

It's very easy to overvolt a arcade board. Another thing, which is very peculiar to the Neo Geo is the ridiculous amount of bad PCB trace faults these systems have over their service life. Perhaps the board traces were too thin?
 
l_oliveira said:
Just mentioning, not related to the OP post, just related to the repair he had to do first. The first thing that blows when overvoltaging the boards are the RAM chips. I believe that is why most times we have to repair boards it's the RAMs that went bad...

It's very easy to overvolt a arcade board. Another thing, which is very peculiar to the Neo Geo is the ridiculous amount of bad PCB trace faults these systems have over their service life. Perhaps the board traces were too thin?
Click to expand...
Usually it's due to a lack of a voltmeter in the cab and the constant swapping between boards. People sometimes forget to dial back the 5v line when swapping out a big size PCB for a smaller one that uses less draw. A good example is, you don't want to run a full Naomi setup then swap in a Neo Geo MV1C without dialing down the voltage.
 
Remote sensing for power supplies has been invented exactly to solve this kind of problem.
It's nothing new actually, yet the business back then was about making everything as cheap as possible for the highest profit possible, therefore remote sensing was probably a luxury nobody would spend money onto. Let alone the need to run a shielded cable in order to make that work properly... Too many people still use wrongly sized wires (and wire count) for power connections even today; I guess making them understand remote sensing would have been asking too much.
 
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