did you swap the lcd to see if you get the same result? generally I end up resorting to probing each signal on each ram and rom chip. Simplification would be to pull all ram modules but the first one.
When using a scope to inspect the signals I toggle reset a lot and watch the signals. when the M100 gets in a stuck state, many of the address lines will be static. Start with D0-D7. make sure they all are toggling at the memory chips. then go through the address lines. The main rom is accessed first. check that ALE and /RD are working as well as the chip select. some ideas anyways On Tue, Dec 5, 2017 at 6:43 AM, Brian White <[email protected]> wrote: > No beep. > > At power-on, RESET_IN on the 80C85 goes from 0 to +5v and stays there > steady. > There is a 5mhz sine wave on X1, and a slightly squared 5mhz on X2, and a > 2.5 mhz square on CLK out. > some of the other pins have square 5v pulses. > > All these chips have +5v on vcc (running on batteries) > chip (pin#) > 8085 (40) > 8155 (40) > 6402 (1) > LH535618 (1) > 6 x HM6117LFP (20) (the individual chips on the ram modules) > > One ram module socket empty > Optrom socket empty > > Double checked I'm doing the blind beep motions exactly right by doing it > on a good unit, then trying again on the bad unit. > > Thank you for giving me the excuse to finally pick up a scope. Got a rigol > dso1054z and unlocked all the options except 500uv. I'm having fun playing > with this thing. Guess I'll finally know how crap the sine wave is on my > various UPS's. ;) > > -- > bkw > > > -- > bkw > > > On Mon, Nov 27, 2017 at 12:48 PM, Brian White <[email protected]> wrote: > >> Can-do. Thank you. >> >> -- >> bkw >> >> On Nov 27, 2017 7:14 AM, "Josh Malone" <[email protected]> wrote: >> >>> I'd start with cold start, hit enter, type beep, enter, and see if the >>> CPU and os is running. Assuming that they aren't, check the reset line with >>> a scope to make sure the CPU is being reset properly on power up and that >>> it's not held low (I think it's active low) since the nimh is in play on >>> this one. >>> >>> Also check power supplies to the various chips. >>> >>> On Nov 27, 2017 12:34 AM, "Brian White" <[email protected]> wrote: >>> >>>> Ok, what do I look at first? >>>> I don't suppose there is a common/frequent/likely answer to that? >>>> >>>> https://photos.app.goo.gl/3MXUjFmttEETro7m1 >>>> >>>> I notice the pattern of bars repeats. >>>> >>>> I have 2 other working 100's and this is a 3rd I didn't really want. I >>>> got it as part of an ebay item where I wanted something else. The nicd was >>>> just starting to corrode but hadn't yet leaked or anything. I've already >>>> replaced it with a new nimh. >>>> >>>> I suppose it doesn't hurt to have a parts doner, but why not at least >>>> take a shot at it eh? >>>> >>>> -- >>>> bkw >>>> >>>> >
