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Mirco 'Challenge' 4 Player Pong - PCB Repair Log #3


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Shane's Board #1

 

I had another Mirco pong clone PCB on the bench, this one had a fault with the horizontal ball control and the score display was messed up.

The paddles dont display if not connected and weren't

connected when testing in the bench.

 

 

I found a 7400 at E5 with a flaky output on pin1 it was removed and tested faulty, after replacing it the horizontal ball control is now working correctly.

 

 

All four score digits were messed up so I went straight to the 7448 7 Segment Display Driver/Decoder and piggybacked it with a working one and the score display was corrected.

After replacing it the board was tested in cabinet and is now 100% working.

 

Edited by Kaizen
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Shane's Board #2

 

This board just showed the image below on screen when first plugged in.

 

Tetk1mz.jpg

 

The 7440 at E4 had a stuck output pin.

 

After replacing it I got an image on screen but the ball was missing, the right side first digit was messed up and one paddle was missing (player 3).

 

Looking for the ball fault first, I checked the 7400 at E5 (same as previous repair) and it had a stuck output.

Replacing it brought the ball back.

 

The next issue to look at was the bad score digit.

 

xjqAWPJ.jpg

 

This was traced back to a 74153 at C8, it tested okay in my component tester but was definitely faulty.

Replacing it got the score working correctly.

 

otPMn3U.jpg

 

In 4 player mode there was one bat missing, a quick check of the counter outputs showed the 74161 at G11 had no outputs.

 

Replacing it got the paddle working, the board was tested in cabinet and is now 100% working.

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