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NBA Jam TE - screen is darker than expected

mathewbeall

mathewbeall

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Hi Folks,

Does NBA JAM TE run dark normally? I am trying to get it to work on some screens, and i really have to crank the brightness up all the way to get it mostly visible, but it still seems too dark to me. I looked at the board and I see some capacitors that look like resistors - so not the normal electrolytic that I would look to see if I need to replace them.

I have tried a few monitors with the same general result.

Thanks in advance for any tips!

Matt
 
Have you cleaned the edge connector (preferably and gently with a fibre glass pen)? I’ve had image problems due to that before - assuming the jamma harness is good with other PCBs.

Are those ‘capacitors’ Mylar types? They usually underperform but can’t tell without a photo.
 
An example of the capacitors on the boarrd.

I will get a fiberglass pen and clean the edge connectors - see if that helps!
 

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mathewbeall said:
An example of the capacitors on the boarrd.

I will get a fiberglass pen and clean the edge connectors - see if that helps!
Click to expand...
yep those Philips caps unfortunately are getting very bad. Williams used these on their WPC pinball games also and the conventional wisdom within that circle is the Philips caps should be replaced, but the iC caps are fine. the latter were used more on Y-unit games, T-unit is when they made the switch to the blue Philips caps possibly exclusively.

otherwise to answer your first question, NBA Jam doesn't run darker than other games. your board was probably just stored in a bad place for a long time. environmental conditions make a difference with this stuff unfortunately.
 
I've had this issue w/ a dirty Jamma edge connector several times on NBA Jam/TE boards.
 
mathewbeall said:
An example of the capacitors on the boarrd.

I will get a fiberglass pen and clean the edge connectors - see if that helps!
Click to expand...
Those definitely need a clean, that could be the cause of your problems. You don’t really need a fibre glass pen, but it’s the best thing I use. I have used erasers, nail files, fine sand paper, etc. you just need something slightly abrasive that will remove the dirt and not scratch the plastic or remove the chrome coating on the contacts. You just need to go carefully.
 
Use the fiberglass pen, and then I pulled out some deoxit and spent about 10 minutes with some papertowels getting off the black residue - its not perfect, but better than before, but alas - when I boot it up - same dark picture.

I am working with console5 to see if they can get me a cap kit.

Matt
 

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Well - thanks to Console5 - I got a cap kit for this guy after a bit of back and forth with Luke on values.... Got the kit today, just did the recap.

Happy that nothing exploded and the game booted right up - but the image is still darker than expected.

The edge is nice and shiny and clean now, and all the caps have been replaced - what else could I look at?

Matt
 
I think I had this problem on one of my NBA Jam boards, replacing the UA4 7407 chip fixed it if I recall. might be something to check.
 
replaced UA4 - same issue... :(

Any other ideas, or things I can do to check - like can I check the voltage on the video signal with the test pattern - like what should blue be with its the full blue screen, etc?

Matt
 
Try removing and cleaning the contacts on the PLCC chips. You’ll need a PLCC chip removal tool to do it properly.

I also use a hook pin to pull the contacts of the PLCC socket inwards to ensure they make good contact with the chip once you push it back in. It’s a tricky process but I am now well practiced in it - just requires patience, practice and care.

It might work…..failing that new PLCC chips but they’re not easy to come by. You could try troubleshooting the video output section of the PCB but that requires repair equipment and some knowledge.
 
I just hooked it up to my tink4k - and at least verified that the levels seem to be low.

When I put in SF2 (CPS1) or my NeoGeo - and look at the red/green/blue levels on a test or artemio 240 test suite page - each color is about a value of 190-210.

On my NBA Jam TE board, each color (RGB) is only about 72 at the max.

So - at least it confirms that I am not crazy, and the value (thus, voltage?) is low.

I am guessing there isn't an easy "this chip is the video amplifier, go replace that" sort of answer.
 
Thanks for finding that repair!

Replace FPGA at UF5.

Replace 74ALS541 at UB4.

Replace 7407 at UA4.

I already replaced UA4 - I just ordered some 74ALS541's and will replace UB4.

If that doesn't resolve it, I will need to try and find a donor board for the FPGA at UF5.

Matt
 
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So - the mystery deepens. I got another NBA JAM TE board - so I can do some comparisons - and the video levels on this one match my original board. when hooked up to the RT4k (to check levels) - RGB top out the same - about 80 (out of 255).

So - maybe the levels I am seeing are just normal? Anyone else have a Rt4k that can check their levels?

I can do a pre-ADC gain of + .8 - that makes it look better, but weird that the levels are low compared to other boards.
 
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