Digital Games 574 (Knock Out) PCB Repair Log

Kaizen

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Donor 2015
Joined
Dec 1, 2014
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Location
Yeronga, QLD, Australia
I got my original PCB back up and running yesterday with only having to fit a new crystal and replace the socket and chip at A1.

https://www.youtube.com/watch?v=DEX0vcXOCzQ

This is the cabinet that was built for it here in Australia.

cf7ZsFCl.jpg


qrj3LPCl.jpg


I spent some time on the spare PCB today and got it fully working as well.
The crystal was missing when I got it a few years ago and it's laid dormant ever since.
The first thing to do was fit a new 5 MHz crystal to it and I replaced the 7400 at A1 as there was no activity on the outputs on the right side, that got some activity happening and a display on screen.
There was only one bat visible and the ball only traveled left in the horizontal direction, no hit detection so instead of rebounding off the walls it just reappeared on the right side.

https://youtu.be/geGvMSn9wps

Replacing the 74139 at 7F got the ball travelling in the upward direction and relpacing the 7427 at 6A got the targets up on screen.

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

Three of the four NE55's that control the bats were faulty as well as a 7400 at 8F and after replacing those I now had all bats visible however one of them would elongate instead of moving when the control pot was turned.

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

There was a dead 9316 (74161) at 7A which was the cause of the bat elongation issue.
Replacing it got that sorted.

https://www.youtube.com/watch?v=B6GWO8kyIQw

Finally there was the issue of no hit detection which turned out to be one of the mystery Xerox 733w00024 (7440) chips at 4A. The game now worked perfectly so I decided to put it into my original cab for the final test.
I powered it up without the board connected and found there was no neck glow, I had this issue previously and thought it was the tube which I swapped with the spare I had. After closer inspection I found it was just a poor connection to the heater.
All fixed and I got to play the first game on this PCB in over 30 years.

https://www.youtube.com/watch?v=eO4SI1IPXQs

Pinout and chip locations below.

tiLtys5l.jpg
 
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