NBA Jam Pcb troubles

[anyeyeover]

I am having trouble with a NBA Jam pcb.  When it is powered up it displays nothing and has no sound. 

A little background on the problem:

I purchased the pcb and sound pcb with no sound cables.  Previously the main board had worked fine (all ROMS checked good) and I played the game with no sound.  A month went by and I finally ordered new sound cables (from bob roberts) and swapped the boards back into my cabinet.  Now it will not work. 

What I have tried/tested so far (to no avail):

-searched for similar problems/fixes on-line
-I am getting full dc voltages on the jamma harness (12v, +5v)
-No bent/touching pins on the solder side of the board
-No visible damage on the component side (my knowledge is limited though).  All chips feel fully seated.
-No broken traces on the solder side
-Everything in the cab works (wiring, monitor, speakers),  This is the only game giving me problems.

Has anyone had similar problems, or common problems with Midway boards? Any help will be greatly appreciated.

[Beretta]

have you made sure the cables are plugged in correctly? ie not backwards? assuming they are'nt key'ed.

[Malenko]

if you take the cable back off does the game start to work?
Do you have the red stripe on the correct side (keyed, as stated above)?


have you tried having just the power or just the data cable plugged in to the sound board?

[anyeyeover]

I have tried the main pcb w/o the sound pcb and no change.  All of the connectors are keyed, I double checked that there is no way to have them backwards.  I will try hooking up the sound cables one by one to see if the problem is in the cables.

Thank you for the replies!

[Kevin Mullins]

Did you measure the voltage at the board ?
(with the board plugged in obviously)

If your 5v is dead on 5 then you might try bumping it up just a little.
(after checking everything else of course)

[anyeyeover]

Hooking up the sound cables one by one (in different configurations) did not resolve the issue.  My +5v is dead nuts on the JAMMA harness, I can try bumping it up a bit. 

What are the two LEDs for on the main pcb board? When the game was working I did not bother to look at which LEDs were illuminated.  Not that it is not working, only the LED closest to the edge connector lights up.  If someone knows what the LEDs are for, it may help in the trouble shooting. 

Thanks for the replies.

[Beretta]

not sure about the leds.

but i have a mk2 board which i think is pretty much the same as nba jam.
the first LED iirc is sold that must me an power..

the 2nd one is sold when i first power up but then starts blinking like mad, iirc it stays sold when in service mode.

i skimmed the manual but did'nt see anything mentioning the led's board checks out fine though.

should also be one on the sound board, iirc the game powers up it will be off, then you'll hear a single "Tone", then the light will come on the sound board, a single tone means sound hardware is ok.

btw have you checked your dip switches?, probably not a issue but just make sure they're what you want and on teh full ON or OFF position.

you might also check the chips push gently down on them make sure they're completely seated..

[Kevin Mullins]

Neither my NBA Jam nor MK2 machines are accessible at the moment..... but I though one LED stayed lit all the time while the other blipped on when booting then was off after that and stayed off unless there was a problem.
(could be mistaken)

[Beretta]

dunno, it might be in the manual some where, did'nt read page by page, mine passes all tests and plays ok so i stopped worrying i figured the 2nd light must be activity on the board of some sort.

although i must admit it is kinda odd for the led to go nuts like that for a normal condition.. i actually thought it was perhaps going bad but it's sold when in service mode *shrugs*

if you find out different though please let me know.

actually now that i think of it the only thing i can think of thats wrong with mine is the NVram battery is dead, thankfully it looks like a standard 2032 lithium battery... i just have'nt bothered to replace it since i'll most likely be putting it up somewhere.