Donkey Kong ghost barrels

servo

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I have been recently having a problem with my Donkey Kong pcb (2 board) as show in this video:

https://www.youtube.com/watch?v=NI4k6GU9fQI

The first blue barrel always doubles and the other barrels glitch and even disappear completely, but are still live in the game. This doesn't happen to every barrel, more like every third barrel but not exactly. I'm wondering if there is some kind of pattern to it im missing, like some kind or binary pattern. It Dose this only on the barrel boards and only with the barrels. Thought it might be voltage at first but i got 5.03vdc steady under load. Tested off an ic leg.

I put the board in my 100% working Donkey Kong Jr. and got the same result

Any help would be appreciated.

Thanks

Servo
 
Thought it might be voltage at first but i got 5.03vdc steady under load. Tested off an ic leg.

I put the board in my 100% working Donkey Kong Jr. and got the same result

good. then you know its the board and not the monitor

turn game on and use the back of your finger to see if any chips are getting hot. hopefully a hot chip can be detected as the culprit. my Jr pac had a hot chip and i glued a heat sink on it and it was fine

look very carefully at the ROM chips and see the condition of all the little legs on there. try and detect any oxidation, dirt, solder splash or even a small piece of metal that is shorting two legs together or anything.

if everything looks ok i would take each ROM chip and CAREFULLY remove it, clean the legs if they didn't look perfectly clean with a dremel tool and soft brass brush
look inside the chip sockets, hit them with the vacuum/compressed air and hopefully theres a little piece of dirt in there causing problems
hopefully you see a bad socket/broken trace and your problem is solved
reinstall the ROM chips and cross your fingers

look at the board and see if there are any broken parts or missing capacitors
a "browned" resistor that looks like it cooked

board is still bad then i would send it out to one of these guys here and hope they can fix it
 
thanks splattergatz, all great advice but i was hoping that maybe someone knew what ram or set of address lines or bit of logic might control the barrels, it only seems to be the barrels. trying to zero in on an area before i start pulling chips. I was hoping that someone had seen this before.

Thanks

Servo
 
made some progress on the board, i hooked it up on my bench and was able to get the barrels right, but i have to pump up the voltage kind of high. to get rid of the glitching i have to have the voltage at 5.4v under load and 6v reading on the terminals of the switcher, don't want to run the game for long like that. anyone have any clue why this board became such a power hog. please help

Servo
 
even more progress this evening, checked the voltage on both boards and the video board is showing much lower voltage then the cpu. check the 5v going out the rainbow cable at p12 and im getting the same voltage that i get on the cpu. once it hits the video board it drops almost a half a volt. so in order to get the video board to 5v the switcher needs to be pumped up and the cpu is close to 5 and half volts. is there some kind of pull up resistor that may be bad, any thoughts would help.

Servo
 
once it hits the video board it drops almost a half a volt. so in order to get the video board to 5v the switcher needs to be pumped up and the cpu is close to 5 and half volts

you can damage chips when the 5v gets above 5.25 or thereabouts so don't do that for very long if at all
those multiboards REALLY don't like the +5v up too high, it kills them very fast for instance

I might suspect a bad pin in the connector if I cant detect any chips getting hot which is what you hope to see so you know which one to replace

if the pin inside the connector is ok then you have to assume something is pulling the voltage down. one would think that running 5 volts directly into the video board, some component has to be getting hot

good luck
 
The old datasheets show Vcc supply voltage as 4.75 - 5.25VDC as the recommended min and max operating voltages.

It also lists as absolute maximum as 5.5V (with 7V for 74LS devices).

I've tinkered with voltages from time to time to get a finicky board working, but I'm uncomfortable running something at 5.2 or above. There are other issues if you need to run higher than that.
 
I've tinkered with voltages from time to time to get a finicky board working, but I'm uncomfortable running something at 5.2 or above. There are other issues if you need to run higher than that.

I checked a spare Popeye pcb using the same rainbow cable and only got a minimal drop of voltage between the two boards, obviously something is pulling down the voltage on the video board. the thing i don't understand is if some chip is shorted, why is the game running without error other then the drop off in voltage. regardless i intend to power the video board up on its own tonight and search for overheating ic's.

thanks for all the input and ill post again one way or the other tonight

Servo
 
tested the board and found three ic's that are hot to the touch, they are three sn74s163 located at 1N, 1M, and 1L on the video board. the schematic looks like it says i could use either s161 or 163. i dont think i have any of these on hand...any thoughts, could this be the culprit? dose anyone know a way of testing them with a logic probe to see if they are shorted?

Thanks

servo
 
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If they're really hot they're most likely shorted. I don't see the harm in replacing them but you never know if its going to fix it. Check your ps really or replace it with the new arcadeshop no hack switchers. (check -5 and if there's ac on the line)
 
replaced and socketed IC's.... Success!!! Kong lives on!

Thanks to all of you for your help

Servo
 
chip is shorted, why is the game running without error other then the drop off in voltage. regardless i in

know a way of testing them with a logic probe to see if they are shorted?

Success!!! Kong lives on!


I'm guessing the barrels are a layer somehow that the game can still run without them showing up ? moving objects that are visually broken aren't enough to stop the game. cool !
wonder if the barrels still killed the guy if they weren't there ??
probably caught the failure in its early stages, no telling what would happen if let to go on
I might've tried to glue a heat sink on the hot chip(s) to see if wicking away the heat better brought back the barrels. had a jr. pac that I did that with a visual problem but the game still ran
couldn't find the chip new but the heat sink worked great

problem with logic probes, you can see the lights on there telling you it's high or its low or even blinking. KNOWING what's supposed to be there, you could raise a family
if you had TWO donkey kong boards, one known working 100% and the faulty one set up next to each other on your test bench all powered up, I suppose you could test one leg of a chip and see what's there with the logic probe and then move over to the other board and see whats the output there on the bad board chip leg.

almost bought an oscilloscope once. probably would have more of these monitor chassis repaired that are laying around here than i do.
I get by ok fumbling through all the "shot gunning" i do without one

look how much you saved just on shipping, not having to have someone else repair it.

good luck
 
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