NBA Jam graphics go woot woot!

jcterzin

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Hey everyone, Hope your weekend will be great.

I've got an NBA jam board that seems to work but when I insert coins the graphics go nuts. basically, all the graphics appear on screen at once, see the pics. Here's the run down.

A) When I start the game up it does a rom check and everything checks out (see pic 1), although it says something like CMOS OK in green and "USING DIPSWITCH COINAGE"
B) then a screen pops up that looks like a tv with static on it (pic 2).
C) The game starts up after I push a button and shows a demo before I insert coins (pic 3).
D) After I insert the coin, the graphics go nuts and I can't start a game (pic 4)

Any thoughts? Is it just that I need to adjust the dipswitches?
 

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Do you get that if its set to freeplay and you just start the game?
 
Looks to me like it's trying to tell you that you need to insert 2 coins to get one credit. It's busy waiting for the second quarter before starting.

Try inserting 2 quarters (=1 credit), and see if that works.

Of course you can change this using the dips. 1 quarter should be, generally, 1 credit.
 
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none of these are normal behavior (well, with exception to the POST screen :p)

the TV should have an animated blowup type thing that says NBA Jam.
the 3rd screen with the bizarre score (2 to 024) is not normal.
neither is the text overlay from what would be the blue NBA Jam screen showing up over an actual game.

you have some kind of error someplace. does the sound ever tweak out where it plays random sounds, or the sound goes out?

I'd start at the roms, particularly inspecting the leftmost roms, the 2 that are offset from the rest (that are closest to the battery), those are your game roms (kind of like a PC .exe). if you've never pulled a rom chip before, I'll explain how anyway...

use a small flathead screwdriver (like a 1/8"), squeeze it between the rom and the socket, but don't use any major force to pull up on the chip. if you pull the chip out crooked, you WILL bend the legs on it. I generally sandwich the screw driver in and give it a little bit of a twist to lift up slightly, then flip around to the other side and do the same thing there. alternate between the two sides until the chip is or is mostly out.

visually inspect the legs that they don't have any dark corrosion on them. this happened on my MK2 and while the game would run sometimes without problem, there were others where the game went completely batshit on me. this corrosion will prevent the data from flowing freely, kind of like a bottleneck, and depending on which pin isn't making good contact will determine what kind of anomalies you experience as a result.

if there's no corrosion, the legs will have a silver appearance to them. if they do not look silver, I've taken some 220 grit sandpaper, and folded it over about 3 times to make it solid, and just run that across the legs in an EVEN pattern until the legs are shiny. then make note of the U-shaped notch on the chip, that should match the U-shaped notch on the socket, ensure that all the legs are in the holes, and then just push down with your thumbs. if the legs are bowed out like /----\ use a flat surface to push the legs flat against and rotate the chip portion downward to bend the legs all in evenly.

I should do a video tutorial on this, seriously.

go around to all your other video roms and push them in with your thumbs too. sometimes it's just a phenomenon known as "chip creep" causing all these weird problems, which is the process by where the heating and cooling cycles of powering the board on and off over the years literally "creeps" the chips out of the sockets slightly.

assuming all goes to plan, your problems may disappear now. if not, then I would look toward it being some kind of logic issue in the CPU, as those are known to break legs off on the T-unit boards from accidental flexing.
 
none of these are normal behavior (well, with exception to the POST screen :p)

the TV should have an animated blowup type thing that says NBA Jam.
the 3rd screen with the bizarre score (2 to 024) is not normal.
neither is the text overlay from what would be the blue NBA Jam screen showing up over an actual game.

you have some kind of error someplace. does the sound ever tweak out where it plays random sounds, or the sound goes out?

I'd start at the roms, particularly inspecting the leftmost roms, the 2 that are offset from the rest (that are closest to the battery), those are your game roms (kind of like a PC .exe). if you've never pulled a rom chip before, I'll explain how anyway...

use a small flathead screwdriver (like a 1/8"), squeeze it between the rom and the socket, but don't use any major force to pull up on the chip. if you pull the chip out crooked, you WILL bend the legs on it. I generally sandwich the screw driver in and give it a little bit of a twist to lift up slightly, then flip around to the other side and do the same thing there. alternate between the two sides until the chip is or is mostly out.

visually inspect the legs that they don't have any dark corrosion on them. this happened on my MK2 and while the game would run sometimes without problem, there were others where the game went completely batshit on me. this corrosion will prevent the data from flowing freely, kind of like a bottleneck, and depending on which pin isn't making good contact will determine what kind of anomalies you experience as a result.

if there's no corrosion, the legs will have a silver appearance to them. if they do not look silver, I've taken some 220 grit sandpaper, and folded it over about 3 times to make it solid, and just run that across the legs in an EVEN pattern until the legs are shiny. then make note of the U-shaped notch on the chip, that should match the U-shaped notch on the socket, ensure that all the legs are in the holes, and then just push down with your thumbs. if the legs are bowed out like /----\ use a flat surface to push the legs flat against and rotate the chip portion downward to bend the legs all in evenly.

I should do a video tutorial on this, seriously.

go around to all your other video roms and push them in with your thumbs too. sometimes it's just a phenomenon known as "chip creep" causing all these weird problems, which is the process by where the heating and cooling cycles of powering the board on and off over the years literally "creeps" the chips out of the sockets slightly.

assuming all goes to plan, your problems may disappear now. if not, then I would look toward it being some kind of logic issue in the CPU, as those are known to break legs off on the T-unit boards from accidental flexing.

Well I'll be... cleaning those two roms actually showed me signs of progress. I no longer have random text appearing all over the place. I still cant tell if the game works or not because I still get no sound and I can't seem to insert coins for some reason. Ill set it to free play and see what happens. cross your fingers.
 
reset all your dips back to their default settings. I can provide this for you, via MAME.

attachment.php


just make note of the dipswitch bank names on the board itself to know.

if you change the coinage to CMOS, you should then either pull your battery out of the board or do a full factory restore.

sometimes this weird shit is caused by NVRAM corruption, I would assume.
 

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reset all your dips back to their default settings. I can provide this for you, via MAME.

attachment.php


just make note of the dipswitch bank names on the board itself to know.

if you change the coinage to CMOS, you should then either pull your battery out of the board or do a full factory restore.

sometimes this weird shit is caused by NVRAM corruption, I would assume.

I will do that. I changed to CMOS coinage and set it to free play and it works! Great news. Still no sound though. I did a check in the sound test and it said "SOUND IRQ" is missing. Also, is there a volume pot or is it in the CMOS as well?
 
there's a volume pot needed too! 50k ohm, you can get one at Radio Shack... not sure what you can do for making a connector for it though.
 
there's a volume pot needed too! 50k ohm, you can get one at Radio Shack... not sure what you can do for making a connector for it though.

Mecha-

Do you have a pic of your sound board. Wheres the pot at? also, which pin headers on the sound board should have harnesses? mine only has the ribbon cable connected to P1. the schematic shows some needed to P5, P6, and P7 as well, is that correct? I don't have those
 
I'm having a simillar problem with my NBA jam, when i got it the sound board was missing the power connectors and volume pot but had the ribbon cable, also to fit it in my cab i had to buy a 12" ribbon cable, i got the power connectors from the man Bob Robers (he also carries the volume pot tho i didn't order it). i can go snap a pic of the wire connections if you'd like.

so is the volume pot required to have sound or just to adjust it? and what is P4 on the cpu board for? i see it has a +5v gray wire that's used and that's it.
 

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are there two cables that go to the soundboard or just the one? I've only got one

Yes there are two cables required to operate the sound board. The first end of the main cable is a 9 pin connector (at header P3 main board adjacent to the jamma connector) splitting to a 4 pin connector for audio output (at header P7 sound board) and 6 pin connector (at header P6 sound board) power input. The volume pot connects to header P5 on the sound board. This main cable provides power to P6 and audio output from P7.

The second cable connector is a 20 pin ribbon cable and is used to transfer data between the boards. Make sure the red edge of the ribbon connects to pin 1 on both boards.

I can see you have both these cables from the attached picture, but you state you only have one?

The volume pot is also essential to operate the sound board. The sound board will not produce any output without it. The potentiometer is usually rated 21K ohms linear for the soundboard.

The P4 connector is used in dedicated cabinet arrangements for service and test switches etc connecting to buttons located around the cabinet coin box area.

I could provide, the exact pin requirements on each header if you need them (e.g GND, 12V, +5V etc)

Hope this helps.
 
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Yes there are two cables required to operate the sound board. The first end of the main cable is a 9 pin connector (at header P3 main board adjacent to the jamma connector) splitting to a 4 pin connector for audio output (at header P7 sound board) and 6 pin connector (at header P6 sound board) power input. The volume pot connects to header P5 on the sound board. This main cable provides power to P6 and audio output from P7.

The second cable connector is a 20 pin ribbon cable and is used to transfer data between the boards. Make sure the red edge of the ribbon connects to pin 1 on both boards.

I can see you have both these cables from the attached picture, but you state you only have one?

The volume pot is also essential to operate the sound board. The sound board will not produce any output without it. The potentiometer is usually rated 21K ohms linear for the soundboard.

The P4 connector is used in dedicated cabinet arrangements for service and test switches etc connecting to buttons located around the cabinet coin box area.

I could provide, the exact pin requirements on each header if you need them (e.g GND, 12V, +5V etc)

Hope this helps.

they're listed at 50k ohm. however, like an asshole, I've gotten away with a 5k once... it was just absurdly loud. I later discovered that it actually called for a 50k. lol

I don't know what to suggest to those that lack the original white block molex connector for the volume pots... ideally you will want the .156 female flat molex connector with the matching .156 pins. just saying. otherwise you're gonna have to ham and egg it by soldering to the back side.
 
great info guys, i think you've found the issue. atleast i'm pretty sure you did with mine. Jon the pic you saw was mine and i have all but the volume pot cable :D jcterzin is missing a cable or two i think.

as for soldering directly to a terminal mecha was just throwing that in there as a "Last Ditch" effort kinda thing, i ordered a replacement volume pot from bobroberts and i'm pretty sure it comes with the molex (or maybe one very simillar to the original) i'll let you guys know when it get's here next week 7.50 + some shipping is a price i'm more than willing to pay for a proper or almost original molex and bob seems to have it locked down lol :D
 
great info guys, i think you've found the issue. atleast i'm pretty sure you did with mine. Jon the pic you saw was mine and i have all but the volume pot cable :D jcterzin is missing a cable or two i think.

as for soldering directly to a terminal mecha was just throwing that in there as a "Last Ditch" effort kinda thing, i ordered a replacement volume pot from bobroberts and i'm pretty sure it comes with the molex (or maybe one very simillar to the original) i'll let you guys know when it get's here next week 7.50 + some shipping is a price i'm more than willing to pay for a proper or almost original molex and bob seems to have it locked down lol :D

if you got it from Bob for your particular purpose, then yes it will come with the connector. I wasn't entirely sure if you got it from Bob (maybe you said it, I'm extremely ill and I'll miss a word or two lol) cause a lot of people suggest Radio Shack, which is fine and all, if you have the original pot to pull the wires from.

and Jon, I agree. learning how to crimp my own molexs = VALUABLE.
 
bob's the f'n man! i had been to his site a few times back in the day but it wasn't till recently that i ordered from him, it's funny i made my first order and by the time i had gotten confirmation i was ready to place a second order.

I'm also a big fan of molex connectors so i bought his crimping tool. it's just great to have a molex quick connector when your swapping out CP's and boards often. i also try and steer away from the shack when possible as they have a hefty markup. although i've given them a fair share of my money when i didn't know any better lol.


completely got off topic, as i said i'll let you guys know as soon as i get the volume pot in what the verdict is.
 
thanks for the replies to all of this, but I'm back to square one. Graphics. I took off two more chips for cleaning and replaced them exactly how they were. Now I get nothing! No images, no test screen at startup. Nilch.
 
Do you have a different game board to try in your cab/test station to make sure it's not something non board related?

other than that maybe another chip came loose? i hate it when your trying to fix something and the thing you were trying to fix worked until you try and mess with it. computers/electronics can be frustrating >.<
 
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