There I had all probes set on 1X and all channels set on 1X to match. I did also have both the probes and scope channels all set to 10X other times and the traces were the same.
Test the ground connection to what? Between the chassis ground and the ground pin of the chip? I had the alligator clip ground references going to the green chassis ground wire via a 10 inch alligator jumper wire, so maybe the long ground wire, or the big metal plate underneath which that wire connects to, picks up noise? The noise is exactly twice the X1 signal so I think it's coming from the M100 itself not from inside the scope or from something else on the bench. It looked pretty bad to me too, but I haven't looked at a working m100 yet, so I don't have a reference to base that opinion on. I am new to scopes, despite the fact that I had a ham license when I was 11 in '81, and then took a couple years of EE in college in 91 or so. I barely remember using an analog scope a little as a kid with my dad in around 79 to 81, but then not again until now. I didn't do any electronics in high school and the ee program I was in was still just theory and math and not a single lab yet by the time I switched to mechanical engineering. So no offense at all :) I'm actually not 100% sure this scope is even good yet. It looks clean and is not missing any parts, and didn't look used at all, but it was open-box from a retail store. There is one thing that I see that I have to figure out if it's a bad AFE or or if it's really something the bad M100 is doing and the scope is just faithfully showing it, or if it's just a normal thing that any scope of this entry-level class will do. What happens is, with everything just sitting there connected up and humming, the entire set of all 4 traces will bob up and down on the screen once in a while. The circuit is an isolated floating battery-powered circuit with no other connections of any type. No power supply, no serial cable etc, so, even if the wall power fluctuated like that, it shouldn't cause the traces to move. All traces move together in perfect lockstep with each other, and only the traces move, not the UI elements, and the shapes of the traces don't change, just move up and and back down, or down and back up. I need to do some testing to prove the scope itself. I need to stick it on a different M100 or some other form of reference signal other than the scopes own built in test signal generator. Maybe both the noisy vgnd and vcc and the bobbing/floating levels are simply evidense of what's wrong with this M100. I just haven't had time to even try some other stuff to do even basic process of elimination yet. -- bkw On Dec 6, 2017 10:58 AM, "Josh Malone" <[email protected]> wrote: A few questions to ask, only because I perceive that you might be new to scopes. If I'm wrong, please don't take offense. * Have you compensated the probes? * Have you checked your ground connection w/ a ommeter? * Have you compared these with what you get using 10x probes? That waveform is terrible! I don't even know what to say. :) -Josh On Wed, Dec 6, 2017 at 4:28 AM, Brian White <[email protected]> wrote: > 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 >>>>>>> >>>> >>> >
