Just playing with my scope. All channels set to the same vertical scale and offset M100 is turned on, powered by batteries, no power supply or any other cables connected. All probes set on 1X and all channels set on 1X to match.
GND REF (probe alligator clips) = green wire by the battery & power jack CH1 = X1 (8085 pin 1) CH2 = X2 (8085 pin 2) CH3 = RESET_IN (8085 pin 36) CH4 = GND (8085 pin 20) (chip gnd relative to chassis gnd just out of curiosity) Not pressing anything. https://photos.app.goo.gl/q47eXNowgVMgVnRv2 Pressing reset. https://photos.app.goo.gl/Nq5h0aFRXGii1CgS2 Consistent with the negative beep test, it also doesn't power itself off after 10 minutes. No new info here, just exploring the scope and the m100. Grabbed the screenshots with netcat! Most sources of 5v and gnd on various chips have that same .8v 10mhz noise. -- bkw On Tue, Dec 5, 2017 at 12:36 PM, Brian White <[email protected]> wrote: > 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 >>>>>> >>>>>> >>> >>
