Q&A Thread

[le basque]

Secondly, what i get 25% of the time with a game (otherwise just black)

[le basque]

And finally the best pics i could get of the pcb :

the front :

[le basque]

and back :

[channelmaniac]

Check the area around the cartridge slot for trace damage. After that, check continuity on data/address lines between the work RAM and the CPU. If that is all good, replace the work RAM.

Raymond

[le basque]

thanks, we'll try that.

[channelmaniac]

Also, check pins on the LSPC chip for bridged solder and other problems as it looks like that chip has been replaced. In the pic it looks like there's something on pins 100-105.

The work RAM is the RAM chips next to the 68000 CPU.

RJ

[DevoDave]

Hey Experts,

I have a NEO-MVH Slot1B (the smallest one I believe).  Lots of SMT.

It's dead.  No video, no audio, and apart from one trace leading from the crystal circuit, no clock.

No damage around battery, and I've run over the boards with a magnifying glass and a fibreglass pencil but averything looks fine.

Can you offer any clues as to what might be causing this?

[channelmaniac]

Check the clock pin on the 68K, and check the sync output on the JAMMA edge connector.

[Artemio]

I know this might be way too late in the thread, but better to have it documented. A few pages ago I asked for teh pinout on CPS 1.5 games, teh ones with QSound. I got hold of another such board, and documented it at: http://wiki.arcades.mx/index.php/Capcom_CPS#Pinout_de_CPS_1.5

[channelmaniac]

Thanks for sharing the link!

[io]

Hello,

I got an MV-4F with some graphical and cart detection problems.
I've read some repair logs here (and there) but it seems I don't have the same board revision.

The board doesn't detect cart in slot 1 and there are vertical lines on the Neo•Geo logo and some in-game graphics (it seems to be on sprites only).
The sound is powerful and clear.
No traces under the battery which wasn't leaking.
Connectors and everything else were cleaned.
There was some kind of oxidation on pins of the NEO-253 chip located in B5 on the top board. I tried to clean that as much as I could and remelted the solders.

I don't really know where to start with those proprietary NEO chips and where to look for each of the two problems.

So if you have any ideas or suggestions, thanks in advance :)

Tools I have at my disposal : digital multimeter, solder station and hot air station.

Some pics :


PS : I've just found a repair log, from you channelmaniac, about this board, so it's the newer revision and seems to be a bitch ;)
Anyway I will take a look and see if it can help me.

[channelmaniac]

Check the address and data lines for the program ROMs on the slot that isn't recognizing the cart. You have signal not making it from the cart to the chipset chip or not making it between chipset chips.

It is most likely a bad trace and it's VERY uncommon for the chipset chips to go out.

[io]

Thank you for your reply.

To narrow my research or not, are every NEO chips connected to every slots (I would say it's logically that way) or are they assigned to one slot ?

[channelmaniac]

It has been a long time... If memory is correct, they each service a slot and they all tie together on their outputs to go to the connectors to go down to the bottom board. That's how the MV4 works.

[hairy otter]

Subject: Troubleshooting vertical lines on the MV6 6-slot system


Not fixed? Next check pin 4 of each 74LS251 for data output. If one is missing then replace the IC.

...

Can't find where it goes to the connector? Check a neighboring 74LS251 IC and see where it goes. If you can find it then check for a bad trace between the suspect data line on pin 4 and the connector to the bottom board and patch it.

Still not it? Check the connection between the top and bottom board. If there is no signal then desolder the connector, disassemble it, pull out the offending connector piece, clean it, reassemble, and resolder it back in place. Test it.

Enjoy!

Hello, I own a 6-slot. It played ok, but it was very dirty. After cleaning it, there are some vertical lines visible.
All slots and all games give the same problem, after looking around on the web I found several documents with all the same text. Wich lead all to here i think.
Now is my problem is it says to check pin 4 for output, but in the datasheet its pin 5 as output. Or do i overlook something?

[channelmaniac]

When in doubt, trust the datasheet. I'm only human.

[TimeWarpGamer]

Hey Channelmaniac,

I wanted to send you some Neo Geo Boards to fix up for me. I have your repair form, but what is the address to send these to?

Thanks and Happy New Year!

[channelmaniac]

PM me here, on the KLOV forums, or on the Neo-Geo forums.

Since I work a day job, I don't post my address online. If I did, I'd be buried in boards!

Raymond

[hairy otter]

Hello Channelmaniac
I already posted my problem and I've tried to fix it, folowing your instructions: http://newlifegames.net/nlg/index.php?topic=152.msg881#msg881
but I got confused.
Al signals on input and output seem fine with the logic probe. But when i tried to find the bad chip by shorting pin 15 and 16. But there is no chip that doesn't make extra lines appear. There is one that changes the look of the problem line so I thought I found the bad chip, but if i let the game play and put it on pause again the lines move to another location and there is another chip that changes the look of the line?
Here is some pictures i found in the thread which look the same as my screen: (I'm not able to make useable  pictures myself )

But on the pictures i found online you can't see if the lines move along with the graphics. On Pulstar for instance all moving graphics seem to have similar issues. Only static and text is fine.
The connection between the top and bottom board are fine. The 6 first (A1-3 and B1-3) and 6 last are shorted together, but I think this is supposed so (GND and +5V?)
Is there anything a can still check?
Thanks in advance

[channelmaniac]

Dumb question: Did you clean the slots and the cartridges?

If so, how?

[hairy otter]

Dumb question: Did you clean the slots and the cartridges?

If so, how?

There are no dumb questions. I did clean the slots and the cartridges, I used alcohol and cotonbuds. But strange thing is all cartridges give the same result in all slots. The symptoms look identical withe the same cartridge in slot 1 to 6. So I don't think the problem is slot related.
But do the lines you describe in your original cure move along with the graphics or do they stay on the same place?

[channelmaniac]

Open the carts and clean the edge contacts with a pink pencil eraser. Q-Tips and alcohol will not remove the surface oxidation from the edge connectors and you will still have poor contact with the slots.

Also, fold over some poster board a couple of times until it is as thick as the cartridge board, lightly wet it with alcohol and insert/remove from the slot a few times. You'll see gunk come out of the slots.

Once you have it cleaned well you will be able to see if it's really a problem with the top board or the carts.

Raymond

[hairy otter]

Hi, I did clean the carts and slots. The contacts of the carts are nice and shiny now. The slots are hard to see if they are shiny, but there was some dirt coming out. I renewed the poster board until it stayed clean. But this didn't bring any solution.
My problem occurred after taking appart the 2 boards for battery exchange and cleaning. This cleaning I did by rinsing the boards with water and letting them dry for a few days. (I cleaned 100's pcb's that way as a daytime job some 20 years ago, without any problems?)

But can you please tell me if the lines you describe in your instructions move or don't?

[channelmaniac]

If you turn Dip 8 on to freeze the system, the lines shouldn't move. If the graphics are moving then the lines will appear to move too.

At this point you should check the outputs of the graphics ROMs on the cart and follow the signals down from the cart to the inputs of the chips on the top board. Then check from the outputs of those chips over to the connectors that send the signals down to the bottom board.

The 4 slot and 6 slot systems use 74LS245 chips or x-to-1 data selectors to latch the various ROM outputs from the selected slot to the connector going to the bottom board. The outputs of those 74LS245 latches for the Program ROMs are tied together and go to the connector. The outputs of the x-to-1 data selectors aren't tied together but all go to another connector to go to the bottom board. Check the outputs of those chips to see if you have one that is racing or stuck high. Check the inputs to see if one is racing or is missing a signal. Check the connector to see if one pin is missing a signal.

For missing signals I use a well calibrated finger on the logic probe tip. This little trick causes bad gates or open logic lines to go crazy when you touch the probe tip to the pin. It allows you to see an instant change on the screen when you touch a pin that is floating with no signal on it or if you touch a pin that has a failure on the inside of the chip.

[hairy otter]

Thanks for your quick response,
OK, if dip8 is on the lines don't move.
But I only tested the 74f251 chips for signals. Are those the x-to-1 data selectors you talk about?
As you described in http://newlifegames.net/nlg/index.php?topic=152.msg881#msg881
They all got signal in- and output. The logic probe I use doesn't light up when floating. So I'm pretty sure there are signals, all give busy, none stuck. I have only one cart plugged in so the signal is coming from the right cart. I also checked the input selection pins and they all give the right bit result.
You say the outputs can be racing? What does that mean? English is not my native language, sorry for that.
I'm now checking connections between the 74f251 chips and the connectors to the lower board, but I don't think there are any bad connections because there turn up new lines if I connect the input to high.
What I get confused about is, if I find the chip that alters the appearance of the lines by taking the input to high and I let the game continue by flipping dip8. Then I put the same input of the same chip on high and there pops up another line along with the problem line?
So I think the problem is further down the line. Where are those signals going to, ones they are on the lower board?
As this is a graphic related problem there is no need to check the 74LS245 and 74LS244 I think?