Good pointers to occupy myself with next at least. Thank you. -- bkw On Dec 5, 2017 7:04 AM, "Stephen Adolph" <[email protected]> wrote:
> 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 >>>>> >>>>> >> >
