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Help! Game Board Repair (Super Pang)
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.
--- End quote ---
Thanks, will have a look over it tomorrow :-)
CHRIS-F:
O.K. Here's what if done so far, I looked over the pcb with a magnifying glass, It's had some previous repairs a few chips have been socketed, and the solder was covered in crappy brown flux, I re soldered those socket pins and a few other suspect looking joint's, I took out all of the EPROM's cleaned the legs with one of those sanding sponges, and re seated them. there was no change it still shows the screen like in the above comment mostly white with blue square. sometimes it boots and sometimes not, I am only a beginner with electronics so don't really know what I'm doing, so I may have done this wrong but I checked the clock on both of the z80's my multi meter has hz and logic, I put the Black lead on ground at the jamma connector and red lead on pin 6 (clk) from memory the meter read 6mhz there is a 12 MHz crystal near by, I think the other z80 is for sound it's near the audio amp and I think that read about 3.75MHz there is a crystal near that that just says 10.000, I checked the 5v pin and that is correct then I checked the reset pin no 26 and one time it was stuck lo but most times it is high.
The interesting thing is if a take a piece of wire and short pin 26 (reset) to ground when I let go it resets and runs almost properly, but wether I reset it by hand or if it boots it's self there is some graphics corruption, when the letters from PANG move around the screen the colours are wrong and not solid they have vertical lines and they only go solid when they come to rest, the super bit at the stop stays messed up.
So where do I go from here? any suggestions, is it most likely two separate problems or could it be the same fault causing both?
Thanks,
Chris.
CHRIS-F:
Anyone know how to proceed with getting this board working? I noticed something weird also, if I plug the machine in it usually doesn't boot properly, but if I pull the jamma edge connector and re seat it the game runs, where should I start looking for why it's not resetting properly, could it even be the z80, I may have a spare, then why are the colours messed up? it's supposed to look like the pictured insert below, when the pang letters are moving round the screen they are also weird colours and not filled properly until they stop moving. I saw a similar repair and it was a ram chip and another was a faulty eprom, I hope it's not an eprom as I have no way of testing/writing a new one.
I can post a picture of the board layout if that helps.
Thanks,
Chris.
Titchgamer:
Sorry I cant offer much in the way of useful advice on PCB repair.
But 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.
Or a bad contact.
So maybe start with that?
I use WD40 electrical contact cleaner to clean all my game carts etc.
Just spray some on a cotton bud and give it a gentle rub then leave to dry.
opt2not:
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.