HELP! Bank Error and ROM Cartridge error

[GadgetUK]

I cannot remember off the top of my head how the banking works, but typically it's going to involve use of one or more of the upper address bits. Since you are getting bad CRCs on both games there, and the banking error too, I would guess that at least one of the upper address lines is not making connection to wherever its supposed to go to the main chipset on the motherboard (with regards to the P bus). Since you are using a 4 slot, there's a lot of buffering logic etc that sits inbetween each slot and the chipset. Since all slots are behaving the same, I would assume from that the clue that a) slot specific buffering of inputs is not the problem b) connectivity between the chipset and the buffering of upper address line(s) could be a problem though. Anyone have any 4 slot schematics? You really need to take a look at the schematics (if there are any) and trace the upper address bits from chipset through buffers etc, and check those chips with a logic probe. My guess is perhaps a faulty 74LS244 or 74LS245, or perhaps a fault on one of the 74LS74 chips. You could buy a spare of each of those types of chips, and try the piggy back method (bend the pins of the new chip inwards slightly, and 'slide' the chip over the top of the chip you want to test - but it has to make a nice snug fit, gripping each pin properly). That technique can often help identify a faulty 74 chip if you've not got a logic probe or logic analyser. Depending on the board, I think some boards use the 'neo buff' chip, which basically is 2 x 74HC245 in one packaged - if you have those you really need to test with logic analyzer, scope or logic probe.

The main thing I would suggest is going over the board with a magnifier really closely and inspect for damage. Broken traces are often the most likely cause.

Also, measure the 5v on the cart slots too. You get voltage drop on these multislot boards and if the PSU is not beefy enough you could measure 5.1v at JAMMA and then 4.8 on a slot... You should measure at least 5.0v on the slot edges imo to ensure its OK.

EDIT: Looking at the schematics that are available (1 slot) - The Neo C1 seems to relate to some of the banking (PORTxxxx) connectivity. Depending on the board you may or may not have a C1 - the logic might be merged with something else. If you do have a C1 I would certainly check around that chip and try and follow its connectivity to (and through) the buffering logic perhaps.

EDIT2: Having said all of that, I just re-read and you are suggesting that several other games work OK? Have you CRC checked those other games to make sure they are coming back OK? If its just these two games and other games work 100%, I would assume its the games themselves or voltage drop related perhaps.

 

[tandrews_ny]

I cannot remember off the top of my head how the banking works, but typically it's going to involve use of one or more of the upper address bits. Since you are getting bad CRCs on both games there, and the banking error too, I would guess that at least one of the upper address lines is not making connection to wherever its supposed to go to the main chipset on the motherboard (with regards to the P bus). Since you are using a 4 slot, there's a lot of buffering logic etc that sits inbetween each slot and the chipset. Since all slots are behaving the same, I would assume from that the clue that a) slot specific buffering of inputs is not the problem b) connectivity between the chipset and the buffering of upper address line(s) could be a problem though. Anyone have any 4 slot schematics? You really need to take a look at the schematics (if there are any) and trace the upper address bits from chipset through buffers etc, and check those chips with a logic probe. My guess is perhaps a faulty 74LS244 or 74LS245, or perhaps a fault on one of the 74LS74 chips. You could buy a spare of each of those types of chips, and try the piggy back method (bend the pins of the new chip inwards slightly, and 'slide' the chip over the top of the chip you want to test - but it has to make a nice snug fit, gripping each pin properly). That technique can often help identify a faulty 74 chip if you've not got a logic probe or logic analyser. Depending on the board, I think some boards use the 'neo buff' chip, which basically is 2 x 74HC245 in one packaged - if you have those you really need to test with logic analyzer, scope or logic probe.

The main thing I would suggest is going over the board with a magnifier really closely and inspect for damage. Broken traces are often the most likely cause.

Also, measure the 5v on the cart slots too. You get voltage drop on these multislot boards and if the PSU is not beefy enough you could measure 5.1v at JAMMA and then 4.8 on a slot... You should measure at least 5.0v on the slot edges imo to ensure its OK.

EDIT: Looking at the schematics that are available (1 slot) - The Neo C1 seems to relate to some of the banking (PORTxxxx) connectivity. Depending on the board you may or may not have a C1 - the logic might be merged with something else. If you do have a C1 I would certainly check around that chip and try and follow its connectivity to (and through) the buffering logic perhaps.

EDIT2: Having said all of that, I just re-read and you are suggesting that several other games work OK? Have you CRC checked those other games to make sure they are coming back OK? If its just these two games and other games work 100%, I would assume its the games themselves or voltage drop related perhaps.

First, thank you for offerring your assistance. I have verified other games and experienced no issues. They passed CRC checks. These two games are the only ones that fail. I will check voltage at the slots.These games BOTH worked fine when I first got them. Metal Slug X had really weird sound, but I hadn't cleaned the cart.

Weird issue is now my buttons seem to be wrong in the bios...they work fine in games but in the bios I end up having an issue where the abcd are the direction keys and the stick is acting like the buttons...So I can no longer get into the test menu. I don't know if its because the system is disassembled, I'm still reassembling it(maybe a grounding issue?).

 

[GadgetUK]

First, thank you for offerring your assistance. I have verified other games and experienced no issues. They passed CRC checks. These two games are the only ones that fail. I will check voltage at the slots.These games BOTH worked fine when I first got them. Metal Slug X had really weird sound, but I hadn't cleaned the cart.

Weird issue is now my buttons seem to be wrong in the bios...they work fine in games but in the bios I end up having an issue where the abcd are the direction keys and the stick is acting like the buttons...So I can no longer get into the test menu. I don't know if its because the system is disassembled, I'm still reassembling it(maybe a grounding issue?).

That's interesting, because the neo C1 also handles input.

 

[tandrews_ny]

That's interesting, because the neo C1 also handles input.

Don't know why, but reconnecting the ground wire resolved it. Now the issue of the cartridges remains.

 

[madman]

I think GadgetUK is on the right track, the 2 games that don't work correctly on your system both use 2 P-ROMs. The others you listed use one. If there is some bank switching or other logic involved to access the data on both P-ROMs that could be the issue. It would explain why your single P-ROM games work fine and why the 2 carts work fine on your friends one-slot.

 

[tandrews_ny]

I think GadgetUK is on the right track, the 2 games that don't work correctly on your system both use 2 P-ROMs. The others you listed use one. If there is some bank switching or other logic involved to access the data on both P-ROMs that could be the issue. It would explain why your single P-ROM games work fine and why the 2 carts work fine on your friends one-slot.

I find it funny they worked when I first got them. Of course it'd failed afterwards. So I guess I need to see if any of those chips get hot? Maybe start probing them? Any tips on where to start? What pins to monitor? I got an old TDS 465 scope.

 

[Pedrobear]

Check /PORWEL, that's the signal latching the bank # into carts.

 

[tandrews_ny]

Check /PORWEL, that's the signal latching the bank # into carts.

Ok, whats the best way to do this? I confirmed I'm getting 5v at the cartridge slot.

 

[Pedrobear]

Not familiar with multi slots, you have to make sure signal output by NEO-C1 is reflected to cartridge slots. (goes through some logic chips right ?)

A good start would be to lift that /portwel pin (95) and apply vcc/gnd to pad and check slots if the same signal applies.

Alternatively, grab a 74ls74 and hoot it up to /PORTWEL, D0 and D1 like bottom right of this schematic:

Hook up LEDs to outputs to visualize if banking is happening.

 

[tandrews_ny]

Not familiar with multi slots, you have to make sure signal output by NEO-C1 is reflected to cartridge slots. (goes through some logic chips right ?)

A good start would be to lift that /portwel pin (95) and apply vcc/gnd to pad and check slots if the same signal applies.

Alternatively, grab a 74ls74 and hoot it up to /PORTWEL, D0 and D1 like bottom right of this schematic:

Hook up LEDs to outputs to visualize if banking is happening.

any chance you know someone i can pay to do this? i dont do well with surface mount and rather not break it.

 

[GadgetUK]

Not familiar with multi slots, you have to make sure signal output by NEO-C1 is reflected to cartridge slots. (goes through some logic chips right ?)

A good start would be to lift that /portwel pin (95) and apply vcc/gnd to pad and check slots if the same signal applies.

Alternatively, grab a 74ls74 and hoot it up to /PORTWEL, D0 and D1 like bottom right of this schematic:

Hook up LEDs to outputs to visualize if banking is happening.

Spot on Funnily enough that's the same diagram I was looking at before my last post lol. Great idea applying VCC / gnd to the pad and test to see if the signal passes through to the cart.

 

[tandrews_ny]

Spot on Funnily enough that's the same diagram I was looking at before my last post lol. Great idea applying VCC / gnd to the pad and test to see if the signal passes through to the cart.

i have an mvs, the c1 is only in the aes? i looked on my board didnt find one either

 

[GadgetUK]

i have an mvs, the c1 is only in the aes? i looked on my board didnt find one either

C1 is on some MVS as well. I guess you've got the PRO chipset? PRO-B0, PRO-C0 etc?

EDIT: Looking at the pinouts (partial) for PRO-B0 and PRO-C0, not sure which chip it would be. I guess you need to look at the pins tandrews_ny suggested (PORTxxxx), and do continuity tests to work out which of the chips connects to them, but it wont be a straight route, I think they are going to go through some of the 74 logic before they connect to the slots.

 

[tandrews_ny]

C1 is on some MVS as well. I guess you've got the PRO chipset? PRO-B0, PRO-C0 etc?

Yeah. I checked around the chips everything looked good, verified nothing was getting hot (shorted).

 

[tandrews_ny]

C1 is on some MVS as well. I guess you've got the PRO chipset? PRO-B0, PRO-C0 etc?

EDIT: Looking at the pinouts (partial) for PRO-B0 and PRO-C0, not sure which chip it would be. I guess you need to look at the pins tandrews_ny suggested (PORTxxxx), and do continuity tests to work out which of the chips connects to them, but it wont be a straight route, I think they are going to go through some of the 74 logic before they connect to the slots.

Ok, so I've attached an LED between PORTWEL and ground on the cartridge. It is always high (lit)...is that right? I haven't had a chance to monitor it with my scope yet because its being a PITA

 

[Pedrobear]

It only goes low on write ops to port region, you wouldn't catch that few µs drop by eye.

 

[tandrews_ny]

It only goes low on write ops to port region, you wouldn't catch that few µs drop by eye.

I used the CRC check, shouldn't I see it flickering?

 

[Pedrobear]

Nope, bankswitching is just 1 write. CRC checking a full 4 banks likely only produce 4-5 writes.

 

[tandrews_ny]

So how should I test this then? I'm obviously getting a signal.

 

[Pedrobear]

As I said, trace back the signal as far as you can through the slots logic gates and apply gnd to the pad (lift component pin), see if it carries through slots.

Also that 74ls74 option to check writes.

You could view the signal with an oscilloscope with some code doing a lot of writes. Probably would need something cutom made, so try other options first.

 

[tandrews_ny]

As I said, trace back the signal as far as you can through the slots logic gates and apply gnd to the pad (lift component pin), see if it carries through slots.

Also that 74ls74 option to check writes.

You could view the signal with an oscilloscope with some code doing a lot of writes. Probably would need something cutom made, so try other options first.

Question, is there going to be one line per cartridge slot? or just one for all 4 with a select line?

 

[Pedrobear]

There's only 1 /PORWEL signal coming from the main system, it's probably run through some logic gates to only transmit to active slot tho. Not familiar with multi slots sorry.

Edit: if all slots are failing the issue is likely before the split anyway, unless a single compolent splits to all 4 slots.

 

[Pedrobear]

All right, just checked a 2 slot board.

/PORTWEL is issued by NEO-C1, enters a NEO-E0 then exits back to both slots. The line is common and active to both connectors. (continuity if you check it with a tester).

I can't speak for a 4 slot tho, you want to backtrack the signal from the slots I guess.

 

[tandrews_ny]

Using my scope, I monitored the PORTWEL line. I turn it on, goes to 5v, right before the error the line goes low for a brief moment. So it seems the line is properly going low.

All right, just checked a 2 slot board.

/PORTWEL is issued by NEO-C1, enters a NEO-E0 then exits back to both slots. The line is common and active to both connectors. (continuity if you check it with a tester).

I can't speak for a 4 slot tho, you want to backtrack the signal from the slots I guess.

 

[Pedrobear]

Did you see the signal shape? Is it decent enough (square angles) or rubbish?


Ok, let's check up banking with unibios.

Use samsho4 and go to ingame menu during neo geo splash screen.

Use patch memory function to bank, write 00/01/02/03 to 2fffff to switch between banks 0/1/2/3. (portwel will go low to latch data)

Manually select a bank via patching then go to memory viewer, and go check address 2ffff0. Hold D to go through faster. It should read 000X (8 times), where X is the bank # you patched in.

Patch in a few bank changes then check the memory value, tell us what's showing up. (not the correct # I guess but meh, let's see exactly)