NBA JAM PCB Video Problem

blazin06

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So I picked up an untested NBA JAM PCB and tried hooking it up in my MKII cab to see if it worked. I get a distorted picture when I boot it. I've tried reseating all of the roms, and cleaned the edge connector. It hasn't helped at all. Any other recommendations/suggestions for me to try? Maybe the board is just bad? I've attached a couple pictures of the screen.
 

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I have a couple T-unit boards (MKII) that have the same issue... Its obviously a sync issue. I haven't tried to fix them because i had so many that i could replace it with.

Would need a schematic or someone else who knows what IC location is responsible for sync
 
First off That PCB has'nt booted up yet.. You can kinda tell its just starting too look though the roms.

I would play with the monitor and see if it changes some how.
 
First off That PCB has'nt booted up yet.. You can kinda tell its just starting too look though the roms.

I would play with the monitor and see if it changes some how.

whoops... Jumping to conclusions.

yes, try the syn pots on the monitor first.
 
it's not uncommon for syncs to vary between different games. even the same games will have different inaccuracies with sync (and other monitor settings too for that matter).

try flipping the sync knobs first. work on vertical sync first, see if the rolling goes from a diagonal motion to just a horizontal one. if that's the case, then adjust the horizontal sync next. all goes to plan, it should work fine then.

I had a cab where the sync wire would slip out of the JAMMA harness when I changed boards in it... verify it's not something silly like that too. I have a couple Midway cabs with this problem.
 
Well I tried adjusting all of the knobs, and it didn't help much at all. Unless there are some more that I'm not seeing that need to be adjusted. I also double checked to make sure no wires had fallen out of the JAMMA harness. Thanks for any more tips you might have.
 

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I was wondering myself if the vertical and horizontal sync cable needs to be paired together. I had an NBA jam and I keep thinking that the horizontal and vertial sync cables were as one. I know you have to do this on some games but I don't remember if this is one.. I looks like his H/V sync's are seperate.. I was thinking that I had one sync cable and it looped to both H and V.. hm.. I could be wrong. Can anyone here look at theirs and see?
 
Well I tried adjusting the 50/60hz knob and didn't seem to help at all... Maybe I'm not adjusting it properly? I tried doing quarter turns and then restarting, never seemed to make a difference.
 
Well I tried adjusting the 50/60hz knob and didn't seem to help at all... Maybe I'm not adjusting it properly? I tried doing quarter turns and then restarting, never seemed to make a difference.

Usually good sync on those is damn near all the way one way or the other.
So if you went fully one way then the other and there was no change then there's not going to be any.
A combination of the 50/60 pot and the Horizontal Hold pot.....maybe.... worth a shot tweaking them both.
 
Here is a above pic, not sure if that helps any. I've tried adjusting both the 50/60 and h. hold together and it doesn't help at all unfortunately. Is it possible one of the rams or roms on the board is bad? Thanks for the help!
 

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We were just wanting to see the video input connection.....namely the three pin section.

Should be something like -
1. White
2. empty
3. Black
 

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Ohhh, gotcha. Almost got it in that pic, haha. Here is one with it. Looks like black-nothing-gray.
 

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Looks right to me.

You could just for kicks take a short piece of wire and strip both ends and jam it in the two sync pin holes to jumper the sync. (loop from the gray wire over to the next hole leaving the gray wire where it is) And then play with the 50/60 and Horizontal Hold pots again.

If that doesn't help, then it's gotta be the signal coming from the board.
 

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Tried what you suggested, still no luck. Must be something with the signal coming from the board. Is there anything on it that I can check that you know of? Thanks again for the help
 
Follow the video input wires from the monitor to the gameboard. You will find a header connection somewhere in the middle. Pull that apart and reseat it and recheck the monitor.
 
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