Various multislot problems

Okay, so I have three boards that I would really like to get working. The first, is an MV4. In the beginning, it wouldn't boot at all. I eventually noticed (After going over it several times) that a 100pF cap next to the PRO-B0 chip at L4 on the bottom board had been ripped off.

Replaced it with one off a parts board, system worked. All four slots are recognized just fine. There's graphical problems however. Every other pixel is missing from everything except the fixed layer. And it's exactly the same between each slot. (With the exception of Slot 2 also having the common vertical lines on sprites problem.)



There are vertical lines where the missing pixels are replaced by pixels of a single seemingly random color, and the color doesn't seem to change.



(These pictures are of the game playing on a 19" LCD monitor)

I have ruled out dirty cartridges and connectors as best I can. The problems don't change regardless of the games or which slots they are in, either.

I believe I have narrowed at least PART of the problem to the top board. After trying again to clean the top board, some of the vertical lines of colored dots disappeared. Now there's only 3 lines. I have yet to run into anything that alleviates the missing pixels though.

I want to suspect the PRO-B0 IC on the bottom board, but until I get the logic probe I ordered earlier this week, I'll have little way to find out. (And I probably STILL won't actually know what I'm looking for.)

Now, about the top board... A lot of the chips on the lower left-hand side (Assuming the JAMMA connector is facing you) are a bit of a mess. They almost look corroded, but nothing I have can get the stuff off, even scrubbing. When it gets wet, it looks like I got it...but it comes right back as soon as it's dry.

And I'm not going at this with soap and water, either. I've been hitting it with some PCB/Contact cleaning spray (Mostly isopropyl alcohol and other things) and scrubbing at it with a toothbrush, rubbing at it with q-tips, and wiping it with paper towels... And it doesn't really seem to be doing anything.

At any rate, I am at a loss here. I went through channelmaniac's repair logs and didn't spot anything that sounded the same. I have no idea what chips I should be eying and where to concentrate my efforts.

Also, what would the stray 1uF electrolytic cap at H3 on the bottom board (A couple inches above the audio section) do if it went bad?

Here are pictures of the MV4's boards:
Top Board - Top Bottom
Bottom Board - Top Bottom

I'll add info on the other two boards (Which I at least have some idea about) later in the thread, right now I think I'm going to go get some sleep.

Looks like a palette RAM address line stuck low. With those random vertical lines though, something else seems up, maybe an electrical sideeffect from a shorted pin. You may be right suspecting B0. I'd reflow the entire video circuit.

+1 on the reflow... Check for corroded plate thrus too.

Looking at the bottom board pic it looks like the battery may be starting to leak. Maybe it's the pic, but it looks a bit fuzzy on top of that battery.

Kyuusaku said:

Looks like a palette RAM address line stuck low. With those random vertical lines though, something else seems up, maybe an electrical sideeffect from a shorted pin. You may be right suspecting B0. I'd reflow the entire video circuit.

Click to expand...

After playing around with the board a bit more, I've found that the vertical lines of colored pixels come and go when the board is rebooted, that is to say, sometimes I boot it up and there's three lines, sometimes I boot it up and there's 20...sometimes none. And they stay put for as long as the machine is on, and only change colors for each game (And the colors seem to come from the game's palette)

The video circuit would be the video SRAM, the palette SRAM, and...?

Now I'm really wishing I had that logic probe, heh. For all I know, none of the SRAM I have to pull from other boards is any good, and the replacement palette SRAM I just got from Digi-Key is SMT... (For a single-slot I'm fixing.)

At any rate, I'll socket any DIPs I end up pulling out so there won't be much labor lost.

A (much) closer look at the PRO-B0 is rather worrying. Whatever is going on with some of the top board chips seems to be going on with the B0, though I think I managed to get most of the pins clean... I just hope I don't need to replace it, since obviously I don't have another 4-slot lying around to take it from.

Any pins in particular I should be checking for continuity?

buaku said:

Looking at the bottom board pic it looks like the battery may be starting to leak. Maybe it's the pic, but it looks a bit fuzzy on top of that battery.

Click to expand...

Yeah, it didn't look particularly like it was to me, but I plan to replace it anyway. Recommendations on a replacement battery? I was thinking a coincell holder and an LIR2032 Lithium rechargeable or the like, but I'm not sure that can be charged safely by the board itself. (For reasons beyond my understanding, Ni-Cd and Ni-Mh backup batteries are proving more difficult to find.)

I think I remember a thread around here that was talking about those kinds of battery issues.

I know others have hooked up cordless phone batteries too if you plan on leaving it plugged in a long time, while others have just bypassed the charging circuit and used a coincell battery.

These are some threads I think I was thinking of:
http://www.neo-geo.com/forums/showthread.php?t=199286&highlight=lithium+battery
http://www.neo-geo.com/forums/showthread.php?t=196121&highlight=lithium+battery
http://www.neo-geo.com/forums/showthread.php?t=183392&highlight=lithium+battery
http://www.neo-geo.com/forums/showthread.php?t=182448&highlight=lithium+battery

No finding a replacement pro-bo from a donor board is no problem as damn near all mobo have that IC. Now your screwed if you ever need a pro-cto


Too the problem at hand, I don't suppose you magically have another working 4 slot around to isolate which board is faulty on the bad 4 slot.

Don't know if this helps, but I have a similar, but way less severe problem with one of my 4 slots. In my case it's the bottom board that's at fault but the problem goes away after the board has power for about 20 minutes and "warms" up.

I just deal with it in my case because I'm lazy.

mainman said:

No finding a replacement pro-bo from a donor board is no problem as damn near all mobo have that IC. Now your screwed if you ever need a pro-cto


Too the problem at hand, I don't suppose you magically have another working 4 slot around to isolate which board is faulty on the bad 4 slot.

Click to expand...

Are you sure about that first part? None of the other boards I have seem to have it. (At least none of my single-slot parts boards, I have a couple of just about every type) Maybe on multi-slot boards. (I would have to get the 2-slotters down off the shelf)

And no, I don't have another 4-slot.

topher said:

Don't know if this helps, but I have a similar, but way less severe problem with one of my 4 slots. In my case it's the bottom board that's at fault but the problem goes away after the board has power for about 20 minutes and "warms" up.

I just deal with it in my case because I'm lazy.

Click to expand...

Yeah, I've had it running for hours straight a couple times now to see if it was that sort of problem, no dice.

buaku said:

I think I remember a thread around here that was talking about those kinds of battery issues.

I know others have hooked up cordless phone batteries too if you plan on leaving it plugged in a long time, while others have just bypassed the charging circuit and used a coincell battery.

These are some threads I think I was thinking of:
http://www.neo-geo.com/forums/showthread.php?t=199286&highlight=lithium+battery
http://www.neo-geo.com/forums/showthread.php?t=196121&highlight=lithium+battery
http://www.neo-geo.com/forums/showthread.php?t=183392&highlight=lithium+battery
http://www.neo-geo.com/forums/showthread.php?t=182448&highlight=lithium+battery

Click to expand...

Thanks, I'll give those a look.

@channelmaniac:

So what chips is it I should be reflowing, and is there anything in particular I should take a real close look at?

The 3 big square surface mount chips.

channelmaniac said:

The 3 big square surface mount chips.

Click to expand...

I was afraid you'd say that. T__T Out comes the soldering workstation!

--UPDATE--

Reflowed all three of the QFPs, well... I know I reflowed B0 anyway, I did the other two with the hot air tool, and I couldn't tell as clearly if it did or not, but the pins and pads look a lot shinier now, so I'll guess it did the trick. Also reflowed the video RAM, nothing changed. :[

So either I didn't completely reflow the other two chips, or the problem is somewhere else. Someone mentioned the palette, maybe I should reflow the palette RAM, too.

There appears to be multiple issues.


There's certainly a palette issue from the changes mid-screen (the purple lines are the correct ones). Since it doesn't effect the fixed layer (which can only use the first few palettes), higher palette address lines must not be brought high.


The every other dot thing has to do with the raster (A0?), I'm not sure how pixels are shifted out to know whether it's a data or address thing though, likely address.

Well, for now, I guess I'm stuck waiting for the logic probe to arrive.

In the mean time, I bought some Shockboxes, and I'm making some very spiffy labels for them. Since I don't have any glossy tabloid sheet handy (My printer CAN do up to 13x44") I've just been printing some smaller spine labels that only wrap ~2" on either side of the spine. Look damn good.

Hand-vectoring some logos in Illustrator should keep me busy. :3


Now I just need to do SS1-SS4, KoF2k, and MSX and I'll be out of boxes, lol

Anyway, back to the matter at hand; When I'm poking around with the logic probe, what am I going to be looking for exactly, or will it be obvious when I find it? As you probably surmised from my commenting on buying a logic probe, I've never used one before. About the extent of my digital circuit diagnostic experience is checking for continuity, heh.

You'd be looking for non-pulsing pins that aren't power. Logic propogates though so honestly a logic probe isn't that powerful at diagnosing digital issues.

That's about what I figured. If that probe doesn't arrive Monday, I'm going to start stabbing people until it shows up. ;<

On another note, got another copy of PUZZLE BOBBLE in the mail today... Another bootleg. That's all three so far. Why in god's name does PUZZLE BOBBLE of all things seem to be the most bootlegged game on the system?? ;<

TheBakachan said:

That's about what I figured. If that probe doesn't arrive Monday, I'm going to start stabbing people until it shows up. ;<

On another note, got another copy of PUZZLE BOBBLE in the mail today... Another bootleg. That's all three so far. Why in god's name does PUZZLE BOBBLE of all things seem to be the most bootlegged game on the system?? ;<

Click to expand...

It's the most bootlegged because it's both one of the smallest (cheap to bootleg) and one of the most profitable games on the system.

Kyuusaku said:

It's the most bootlegged because it's both one of the smallest (cheap to bootleg) and one of the most profitable games on the system.

Click to expand...

I call shenanigans!

On the bright side, of the three boots, one is a straight-up boot, nothing in it but EPROMS and flash, albeit on legit boards, but the others used to be FF Special and FF3, neither of which I have, and still contain like half their original mask ROMs... I guess it wouldn't be so bad to reclaim one or both with strategic use of an EPROM burner. :3

btw, logic probe arrived just a little while ago, so no one's going to get stabbed....this time.

btw, how do I get to the palette RAM with the boards together? I was under the impression that the board shouldn't be powered with the two separated. ;o (Or maybe that was that they shouldn't be separated with the power ON, but I would think that would go without saying.)

TheBakachan said:

btw, how do I get to the palette RAM with the boards together? I was under the impression that the board shouldn't be powered with the two separated. ;o (Or maybe that was that they shouldn't be separated with the power ON, but I would think that would go without saying.)

Click to expand...

That's a good question... I guess to start you should probe the solder-side pins. It's probably OK to power on the bottom board separated. I dunno if the BIOS will start though/everything won't crash.

Well, my first attempts did not locate anything I could see as a problem.

So, I now have this Logic Probe and a Logic Pulser. The logic pulser can apparently inject a pulse into a circuit using one of two pre-set intervals, OR an external source. Does this mean I can theoretically use it to inject a known-good signal, and keep trying points along the circuit until the missing pixels are filled in? (Thus determining that the data goes missing somewhere between there and the SRAM)

As an aside, does that mean I could theoretically use the pulser to inject a 32.768khz pulse on a board I suspect of having a bad crystal and see if that gets it to boot? (Granted, it would probably take about the same amount of time to just replace the crystal and see...)

So all palette RAM lines were pulsing? If so then you've got to look at whatever multiplexes palette RAM (I think B0), keep traversing the circuit.

You don't want to inject a pulse, that will only weakly drive an input and have no effect in this case (all outputs can overpower the pulse).

topher said:

Don't know if this helps, but I have a similar, but way less severe problem with one of my 4 slots. In my case it's the bottom board that's at fault but the problem goes away after the board has power for about 20 minutes and "warms" up.

I just deal with it in my case because I'm lazy.

Click to expand...

Sorry for the necropost, but this is the only thing i've found on the net so far related to my exact same issue.

Slot 4 on my machine seems to have these "static" spots whenever I first start up the machine. It does seem to ease off after the machine has been on for around 15-20 minutes or so; but has there been a fix (or even a diagnosis) found out for this yet?

Zombie Shoes said:

Sorry for the necropost, but this is the only thing i've found on the net so far related to my exact same issue.

Slot 4 on my machine seems to have these "static" spots whenever I first start up the machine. It does seem to ease off after the machine has been on for around 15-20 minutes or so; but has there been a fix (or even a diagnosis) found out for this yet?

Click to expand...

No brainer if its a time related issue on a single slot, its a faulty IC less likely the actual connector.

mainman said:

No brainer if its a time related issue on a single slot, its a faulty IC less likely the actual connector.

Click to expand...

I appreciate the quick response. Any idea how to fix this issue (if there is a way)?

Sorry to be such a pain in the ass, I just recently got my cab and am completely new to this. The most I was able to do was fix/replace the buttons and sticks and clean the MVS carts that came with it.