Wednesday, 15 March 2017

Karate Champ (bootleg) pcb repair

I've had this one stored away for years and now finally got around to making a jamma adapter for it. It just displayed a screen of static garbage, it looked like the cpu (Z80) wasn't running so started there. The clock and reset were working so next I removed the cpu as it was socketed and checked it in my tester, it was fine.


I then moved on to the TTL chips surrounding the cpu, I found a 74LS245 @C12 with two output pins (11 and 13) stuck low and all the inputs were pulsing away nicely. I cut these two pins and checked them with a logic probe at the board and the lines were now floating instead of low, this confirmed that the 245 was bad and that it wasn't something else on the lines forcing them low.

 Socket and new 74LS245 fitted.


After replacing a few damaged capacitors repair complete.

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