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Opto problem


prowler

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An error message comes up on my HS2 which says "gnd. short row4 white/yellow r4". Now i have found that 1 of the 5 optos isn't registering when i have it in test mode. There is power going to all the optos, even the one that isn't registering. Could it still mean there is a ground problem or is the opto stuffed?
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An error message comes up on my HS2 which says "gnd. short row4 white/yellow r4". Now i have found that 1 of the 5 optos isn't registering when i have it in test mode. There is power going to all the optos, even the one that isn't registering. Could it still mean there is a ground problem or is the opto stuffed?

 

The gnd short errors are not usually a gnd short!

 

Has the U20 been replaced? I think it is the most common one to go on these.

 

On mine, an opto which was flakey just needed a good clean with cotton tip.

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Can you explain what you mean "test the opto 12v uncovered 0v covered". Also which u20 are talking about?

 

UPDATE: still have the opto problem, now the up/down shifter is playing up. Up shift works but down shift dosen't. It just makes the sound of a car starting. Also when i turn machine on and close coin door the same car sound starts and won't stop till you open coin door. This all makes me think it has something to do with the CPU board. I bought the machine with the board badly corroded. I'm hoping the board is the culprit.

Edited by prowler
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Another way to test the opto receiver is using a DMM. First block the opto transmitter with a piece of black electrical tape. Put the black DMM lead on ground (the metal side rail of the game works well). Put the red DMM lead on one leg of the opto receiver (gray wire). One opto receiver leg should show 12 volts DC, and the other opto leg should show close to zero volts (orange wire). Keep the red DMM lead connected to the "low" (zero volt) opto leg. Now shine a flashlight into the opto receiver. The DMM should now go to 12 volts DC, and when the light is removed, go back to near zero volts. If this does not happen, the opto receiver is bad. Or if 12 volts is seen on both opto receiver legs, the receiver is bad (or there is direct light shining into the opto receiver).
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I had the same problem on my Indiana Jones (except it was Row 1 not 4), followed the pinrepair guides and unplugged the opto boards under the playfield one by one until the error stopped.

 

Once i had isolated it to a particular board - it was the 10 switch opto one - i replaced the 3 LM339 ICs - total cost about $8 from Jaycar. I also soldered sockets in case these chips fail in the future.

 

I was pretty certain it wasn't the switches or opto's as these all seemed in perfect nick and all had continuity.

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