Here is a repair of a Williams Defender video game. This brings back fond memories. I was invoved with helping Williams get the bugs out of the prototype first rom boards. I remember the production line sent them out with the wrong control interface board for the proto roms, the fix was to upgrade the roms. This particular game had a great looking cabinet but was just not wanting to work for the customer. The repair notes follow:
12/23/2016 Initial check out - dead monitor, power supply needs work. Repaired power supply but the connectors all through the game are corroded and making bad connections. Will replace pins and plugs next.
12/26/2016 Replaced header, housings and pins on all power plugs on power supply, CPU board and Rom board. Installed extra +5 and ground connection on CPU board. This brought the +5 up from 4.3v to 4.84v. Now the boards run. The monitor works, the brightness was just turned down. After 10 minutes the boards locked up or reset the game. Cleaned all IC's in sockets and verified all roms on burner. Seems to be working, testing. The sound board has a hum, will change the caps. Replaced ruined battery holder with an off-board unit on wires.
12/27/2016 Changed all caps on the sound board and replaced the input power plug and the sound select plug. The marquee light ballast was very hot, had the wrong bulb (a T12 instead of T8), replaced ballast after it destroyed my first T8 bulb inserted, replaced bulb and starter. Found 2 incorrect fuses in power supply, over-fused. Re-install monitor. Dress all wires. Testing.
12/27/2016 Changed the locks. Note: the bad ballast/starter/bulb was effecting the game with video glitches and the ballast was probably causing loads on the AC line. This being an analog power supply a marquee light can cause issues like lock-ups. The game works great. Ready to go.
12/30/2016 After 6 hours burn in the game locked up showing Ram Error. Built a test jig to run the boards on my bench (including a 7404 IC to invert the positive sync to negative sync, found composite sync on pin 7 of plug - un-populated & undocumented). Tracked down Ram 23 bad, re-installed board in game. Ran the game all night, it locked up again. Put it on the bench and it worked, suspect a bad socket, cleaned all sockets with cleaner, cleaned 6809 cpu rusted legs. Testing in the game again.
01/01/2017 Ran game all night, locked up again with ram error. Ram is not bad, on a hunch replaced the sockets on the 2 Video Decoder mask roms (7641 type) with high rel machine pin sockets. Tested 18 hrs, still working. Still testing.