Problem with my NBA Jam - weird flickering crash

sixteenbits

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I'm hoping someone can point me in the right direction with a crash I'm having with my NBA Jam cabinet. It's not an official Midway cab, but it's fairly well built.

Here's the problem: During play (or more typically, a few seconds after turning the machine on) the screen will begin to flicker. It looks like a few lines of gray static. A repeated "tick-tick-tick-tick-tick" can be heard coming from the monitor. I lose all game audio too, so it's as if the game crashed outright. Sometimes the game will reset, but lately it's just been hanging at the flickering. I'll turn it off and then on again, and it will either (a) crash again immediately, (b) make the "bong" sound and then crash a few seconds after the splash screen comes on, or (c) play normally and be just fine. However, (c) is happening less and less and (a) is happening more and more.

When it works, everything is great - no issues with video, audio, or controls. Which makes me think it's not the monitor. Could it be the CPU? That's probably the newest (at least in look) component in the system. PSU?

For a while I thought it was perhaps a grounding problem. The ground wire inside the machine wasn't rigged very well. It was crashing immediately upon startup so I unplugged it and futzed with the ground wire. Then, lo and behold - out of the blue, it worked. Played 3 straight games, no problem. Unfortunately, that didn't last. I left in on the attract screen for 20 more minutes and the flickering started again. Right on bootup too. No "bong" sound on startup. I messed with the ground cable a bit, but I'm not getting results like I did yesterday.

The only other thing I did was move the cabinet to access the back. Perhaps something is loose?

Does this ring a bell for anyone? I'm totally stumped!
 
I had something similar with my MK2 (same T-unit hardware) and you'd be amazed at how simple the solution was: just take your board out and press down on all the roms, make sure they're seated in the sockets well. do this on the sound board too.

cause my MK2 would reset or the sound would cut out or act 57 varieties of stupid until I did that.

it's a good precautionary place to start, if anything.
 
I'm not sure why your monitor would tick....that's odd but throw the diag switch on that board to boot it to the diag menu. First thing I would test is the hard drive.
 
If the CPU can't boot the watchdog circuit will whack it repeatedly in an attempt to get it to boot. (Reset line periodically pulses) This can translate to a tick-tick-tick sound that comes generally from the speaker but can also come from the monitor if the sync comes and goes with the reset.

Reseat the socketed chips as was already mentioned as a first step in troubleshooting.

RJ
 
I had something similar with my MK2 (same T-unit hardware) and you'd be amazed at how simple the solution was: just take your board out and press down on all the roms, make sure they're seated in the sockets well. do this on the sound board too.

I did this and it seems to have helped! This morning when I turned on the machine it went straight to the flickering. I did what you mentioned just now and was able to play 3 games so far with no issue. It's on attract right now, hopefully it lasts! I wasn't sure if it would work because the Roms seem to be affixed to the board pretty snugly and didn't seem to move when I pressed on them. But so far, so good.

There's also kill switch in back that shuts off power if the rear door is opened. I wonder if that has something to do with it. In other words, maybe the switch was neither on nor off, but somewhere in the middle? I taped it down just in case. I probably should have tried to isolate the cause, but if it happens again I guess I can revisit that.


I'm not sure why your monitor would tick....that's odd but throw the diag switch on that board to boot it to the diag menu. First thing I would test is the hard drive.

I ran through all the diag screens, everything checks out ok. There's no hard drive in the game but it gets through the CPU check with no problems. I see there's a hook for a slam tilt switch, but I don't have one set up. Could that have something to do with it, I wonder?
 
I did this and it seems to have helped! This morning when I turned on the machine it went straight to the flickering. I did what you mentioned just now and was able to play 3 games so far with no issue. It's on attract right now, hopefully it lasts! I wasn't sure if it would work because the Roms seem to be affixed to the board pretty snugly and didn't seem to move when I pressed on them. But so far, so good.

There's also kill switch in back that shuts off power if the rear door is opened. I wonder if that has something to do with it. In other words, maybe the switch was neither on nor off, but somewhere in the middle? I taped it down just in case. I probably should have tried to isolate the cause, but if it happens again I guess I can revisit that.

if you ever want to bypass the interlock safety switch, snip your wires and splice the same colored ones together (I'll assume it's either white and black wires or a blue-ish grey and brown) ... just match the whites with whites and blacks with blacks (or whatever colors they are) and you'll never have to worry about that switch again. :) I did this on my PlayChoice-10 for the stupid coin door switch, it works.




I ran through all the diag screens, everything checks out ok. There's no hard drive in the game but it gets through the CPU check with no problems. I see there's a hook for a slam tilt switch, but I don't have one set up. Could that have something to do with it, I wonder?

he might've thought you were talking about NBA Showtime (the hard drive).

I don't think the Slam switch does much of anything. you would think on a hard drive based game like Killer Instinct that triggering the slam switch would make it reset, but it doesn't. so... kind of pointless, unless I'm missing something?


glad it worked out though. those T-unit boards are pretty dick-like. imagine what I go through shifting my MK2 around with that big expansion board on top. :D hope it holds up for you!
 
It's happening again :(

I thought I was out of the woods but the issue seems to be back. It's not as bad as it was before - now, it's just quickly flickering and then reseting. I'm going to try pressing down on the ROMs again, but I wonder if there's anything else I can do? The CPU diag checks out OK...possible my board is screwy? Maybe it's something else?

Do the ROMs come off? I think so...Maybe I need to pull them off and clean the legs with a pencil eraser...
 
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if you ever want to bypass the interlock safety switch, snip your wires and splice the same colored ones together (I'll assume it's either white and black wires or a blue-ish grey and brown) ... just match the whites with whites and blacks with blacks (or whatever colors they are) and you'll never have to worry about that switch again. :) I did this on my PlayChoice-10 for the stupid coin door switch, it works.


Heh, I have a black w/ white stripe, red w/ white stripe, tan, and white. Go figure.
 
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