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Author Topic: Help! Game Board Repair (Super Pang)  (Read 169 times)

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CHRIS-F

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Help! Game Board Repair (Super Pang)
« on: June 12, 2019, 06:01:33 am »
Hi All,

I only bought my Super Pang (Bootleg) PCB a week or so ago and it worked normally, I removed my joysticks to clean out the gunk and swap a few Switches, everything worked with the machine open, I unplugged it and all I did was push the PCB back a little on top of it's plywood shelf and close the machine up, after switching it on again there was a horrible sound coming from the speaker and the screen showed a corrupt white screen with light blue blocks, I switched it off and on again and I saw a message saying RAM OK with lines across the screen, after switching it off and on again a few times I get different screens with corruption and sometimes the game seems to work, but there is no sound, about one time in ten it will start and work normal, sometimes at switch on it seems to be making corrupt sounds like in attract mode, but AFAIK attract mode sounds is off so it shouldn't be doing sound anyway until a coin is inserted, my initial thought was I may have pulled a solder point loose when sliding the board along the wooden shelf, but I can't see any loose.

Where do I go from here to try and diagnose the fault, I have a multimeter, (I think it has logic test) and I have checked I'm getting about 5.1V at the chips and just over 12V (forgot the exact voltage) but the voltages seem to be correct.

Thanks,
Chris.

Mike A

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Re: Help! Game Board Repair (Super Pang)
« Reply #1 on: June 12, 2019, 06:47:47 am »
I am not an expert at this, but the first thing I always do when a board suddenly stops working is clean the edge connector and plug it back in. That has worked a surprising number of times. I have had two boards where I cleaned and re-seated any chips in sockets. That fixed them up. This would be a good starting point.

CHRIS-F

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Re: Help! Game Board Repair (Super Pang)
« Reply #2 on: June 12, 2019, 07:28:35 am »
I am not an expert at this, but the first thing I always do when a board suddenly stops working is clean the edge connector and plug it back in. That has worked a surprising number of times. I have had two boards where I cleaned and re-seated any chips in sockets. That fixed them up. This would be a good starting point.

Thanks Mike,

I have cleaned the edge connector with a scotch pad and IPA and wiggled it on and off a few times, still no change, also I have re seated all the EPROMS. I'm leaning towards a logic fault maybe as the only thing that makes it work is powering it on and off a few times, each time is different but it occasionally works ok.

Mike A

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Re: Help! Game Board Repair (Super Pang)
« Reply #3 on: June 12, 2019, 07:32:45 am »
Yeah. It is time to get down and dirty then. Pretty much anyone will know how to proceed better than me.

opt2not

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Re: Help! Game Board Repair (Super Pang)
« Reply #4 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 way to check this is by turning the game on and tapping or lightly pressing on some of the surface mount components.  If you see a change on-screen, there could be cold solder on those components, or they're failing.

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 (horizontal storage should be avoided as gravity will eventually make your PCB's sag).
If something changes on-screen while you're lightly bending the board, there is most likely a cold solder joint somewhere.

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Re: Help! Game Board Repair (Super Pang)
« Reply #5 on: June 12, 2019, 06:04:03 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.

Thanks, will have a look over it tomorrow :-)

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Re: Help! Game Board Repair (Super Pang)
« Reply #6 on: June 14, 2019, 01:28:25 pm »
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.