My meter has some limited scope capabilities. I'll start tracing everything down and see what I can find. The clock is definitely working and the CPU is getting a 2.37mh signal. But I have not checked all the control lines yet. I'll check and post the results.
Kurt On Sat, May 25, 2019, at 5:22 AM, Stephen Adolph wrote: > Kurt, do you have a scope? > I would certainly try reseating any socketed parts. Main rom is socketed for > sure. > Then I would start at the clock and work forwards. > * verify the CPU has clock > * verify the CPU control lines are toggling > * look at the address and data lines for toggling and level > > if that all looks ok then, pin by pin on the main rom, check for toggle and > level. > again for the ram modules. > to make it easy remove as many ram modules as you can. > > check DC on the power supplies of course. > > On Fri, May 24, 2019 at 8:41 PM Kurt McCullum <[email protected]> wrote: >> __ >> I've got two NEC 8201s that are both dead. I'd like to get them up and >> running again. Especially the one with the Japanese keyboard. Has anyone put >> together a list of what to check to diagnose where the problem might be. I >> have done the power supply test from the service manual and the CPU seems to >> be correct but I'm not sure where to start. Both units turn on with a blank >> screen. >> >> Kurt
