Sunday 4 October 2015

Quick Atari Jet Fighter Repair

So I moved my games around today making space for a new cab and upon turning Jet Fighter back on the score for the white Jet was missing form the display.

A quick browse at the schematics led me to the section below:

/Score1 is the Video signal for the black Jet score and it was pulsing away on my logic probe. /Score2 was for the white Jet and that output (Pin 3 of C3) was stuck high. I checked the input signals and they all looked good so I piggybacked C3 with a new 74LS00 and the score came back. 

I removed the bad chip, fitted a socket and popped the new 74LS00 in and everything is working again.