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Help! Game Board Repair (Super Pang)
CHRIS-F:
--- Quote from: Titchgamer on June 18, 2019, 12:27:14 pm ---Your comment about pulling and reseating the jamma connector is a good indicator that either the board contacts need cleaning or the jamma connector does.
So maybe start with that?
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Yeah! I thought it could be a bad connection, but I've cleaned it twice now and still the same, it doesn't boot on it's own but If I short pin 16 (Reset) on the main Z80 CPU it shows the ram ok and boots normal (apart from the graphics corruption), so I'm leaning towards a faulty reset circuit, I'm only a beginner with electronics so it's not easy to trace stuff, I tried to follow the reset line but it goes through a few through hole points and then I only got as far as the same pin on the sound CPU another Z80 and a little further to an ic, I checked the pinout of that IC but it's not something I'm familiar with so I gave up :-( I will try again this time taking note of the IC and writing it down.
CHRIS-F:
--- Quote from: opt2not on June 18, 2019, 03:01:21 pm ---Yeha, wish I could help out too, but I don't know what's going on with those bootlegs. I have an original PCB of Super Pang with different sprite issues, and have an idea of where to look on my board, but I wouldn't be able to tell you what to look at on a bootleg.
On the original boards there are 2 major customs that deal with sprite generation. If you could determine where the graphics generation circuit is located on your bootleg, I'd start probing IC's for stuck or dead logic on their data pins.
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I know this pcb differs quite a bit from a genuine Super Pang, but any idea where about to start looking? I would like to first fix the reset problem, the board wont boot by itself but resetting it by grounding pin 16 on the cpu gets it running, I'm Guessing something is being stuck hi/low just don't know where to look.
Thanks,
Chris.
CHRIS-F:
--- Quote from: opt2not on June 12, 2019, 04:26:34 pm ---It's possible you might have scratched a trace when moving it around in your cab. I would go over it with a magnifying glass and look for scratches or gouges that might have torn traces.
Another possibility, shifting around an older PCB can sometimes knock the legs of the surface mount chips loose. I've had this happen to my Smash TV board, when it was shipped to me.
One last "physical" test you can try is light bending the PCB a bit when it's running. Sometimes these boards get flexed over time, especially if they're stored improperly.
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You were only right :-) Moving the board had moved a trace that was lifted, not only did it move but it had broken in two, I only found this after killing two CPU's :-( I also found a dry joint and a few areas on the board where previous repairs weren't done so well, some of those traces run really close to IC pin solder pins and the crappy flux was all over the area, the protective covering is also missing on some traces, I had a hard time tracing the reset circuit as it runs under soldered in IC's, but eventually found the Ceramic resonator has had legs soldered on and was only touching intermittently, ordered a new one from the USA but in the meantime it's bodged.
I'm now Happy that my board is working properly and as a bonus I even figured out the dip switches although I can't notice any difference selecting Easy, Hard, Very Hard, Normal :-)
A further question though, is it normal for some of the IC's to get warm/Hot? I noticed a few get quite warm, I might get a thermocouple on and see how hot and which particular chips, its possible that there may be some more shorts somewhere on the board unless it's perfectly normal for them to get hot.
Thanks again everyone for your help.
Titchgamer:
Well done figuring it out.
And yeah its normal for IC’s to get warm.
opt2not:
Nice job on the fix! These fixes are the easy ones, you’re lucky you didn’t have to replace IC’s. I wish all my fixes where like this.
Glad this got sorted. :cheers: