This is the second Lethal Enforcers PCB I fixed and also in this case it has been a pretty easy repair .
Board was mint and clean:
When powered up it I got this screen:
Screen was static but from the clicking sound I understood that watchdog was active so, for first, I disabled it by closing jumper ‘JP’ near JAMMA edge.In this kind of Konami hardware (like in many others) RESET is generated by pin 10 of the SIL custom ‘051550’.Probing this revealed that signal was good (first LOW and then HIGH) while RESET line (pin 37) of the main CPU HD63C09EP was stuck LOW.I traced it back to a 74LS367 @N6 which output was good and input of this to an output (pin 13) of 74LS164 @H3.Tested this with HP10529A logic comparator revelead bad outputs (pin 11, 12, 13).
So I desoldered and tested it in my EPROM programmer and B&K Precision 560A IC tester which confirmed it as bad:
Replaced it fixed the board completely.
2 Responses to “Lethal Enforcers repair log #2”
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Interesting, how often you use the logic comparator? is it always give true result?
i might consider to get one if they’re good.
Hi.Logic compararator is a good piece of equipment but, like others, is not perfect.It has some limitation in testing some IC like flip-flops and counters that can run too fast for it or tri-state devices with outputs tied to a common bus so it can give false results.Anyway, I’d recommend you to get one of these for your arcade repairs.