oh and yes the scope is grounded, and the m100 is free floating on batteries only
On Dec 12, 2017 8:25 PM, "Mauro Pintus" <[email protected]> wrote: > Hi, > I have a *not working* Olivetti M10 and a Rigol DS1104Z oscilloscope, > so I made few measurement to try to help Brian and in the mean time try to > troubleshoot my unit. > > My unit was working properly and stopped as soon as I flipped the NiCd > battery switch off while the unit was ON (done by mistake with the cover > open). > Now the screen turn on but I can regulate just the contrast and no text > appear on the screen. > I also made a small arduino circuit to test the LCD alone, and I'm able to > write text on it, so the LCD should be fine. > > BTW I think Brian is using way too long ground leads on the oscilloscope > probe. > I made my measurement clipping the alligator clip to the metal case of the > main crystal that in the M10 is grounded with a pice of bare wire. > Is your scope grounded? I can see in one of your pictures the usual US > plug with only 2 terminals... > > Here are some screenshots of my measurements. > > https://photos.app.goo.gl/8YSbaAxZBuXu5rjC2 > > Pictures: > 1) CLK pin 37 of the 8085 > 2) Pin 7 of the 8085 > 3-4) CS Pin 20 of the ROM it seems to cycle over and over > 5) Reset * at power on > > VEE is 4.9V > V across the battery is 4.02 when the unit is on and 3.9 when off > > Tomorrow I'll continue hoping Brian or some of you can confirm/compare > some of my measurements. > Have a nice day > Ciao > Mauro > > NOTE: I think I will measure all the pins on the system bus so anyone with > an oscilloscope can do the same without opening the unit case... > > > > > > On Dec 11, 2017, at 9:28 AM, Fugu ME100 wrote: > > Ah the “special tool” requirement always hated to see that in any step….. > > What did the –5V measure on the meter? If it is not within spec neither > the LCD or buzzer will work. > > From: M100 <[email protected]> on behalf of Brian White < > [email protected]> > Reply-To: <[email protected]> > Date: Sunday, December 10, 2017 at 11:30 PM > To: <[email protected]> > Subject: Re: [M100] Fwd: Re: diagnose > > Thanks for that tip. > > And oh like some GM repair manuals where replacing an entire transmission > might be 11 steps, but one of them is to use the $12,000 machine no one > outside of the factory has ever even seen. > > > On Dec 8, 2017 1:38 PM, "Fugu ME100" <[email protected]> wrote: > >> It might be better to use the CLK (37) output as a reference if it is >> needed. The CLK is derived from the X1,X2 XTAL inputs and should not be >> impacted by the loading of the scope probes. >> >> The M100 reference manual is quite good for troubleshooting some parts, >> although it does have a few broad instructions like “Check All IC’s”. >> :-) >> >> From: M100 <[email protected]> on behalf of Brian White < >> [email protected]> >> Reply-To: <[email protected]> >> Date: Friday, December 8, 2017 at 9:55 AM >> To: <[email protected]> >> Subject: Re: [M100] Fwd: Re: diagnose >> >> I noticed something a couple days ago. Those noisy gnd and 5v lines were >> only like that because I happened to have probes on both X1 and X2 at the >> same time. >> >> Later I was looking at a good M100, and happened to only be watching X1 >> and others but not X2, and everything was much better. But just by touching >> a probe to X2 while another was on X1, both gnd and 5v went exactly like >> those pics I posted from the bad M100. I can probe either X1 or X2 and it's >> fine, but not bith at the same time. >> >> I don't actually see any special reason to monitor either of those >> signals except briefly to verify they exist, or to provide something steady >> to trigger on while probing others. Just pointing out something I saw that >> explains those ugly traces. >> >> On Dec 7, 2017 11:45 AM, "Josh Malone" <[email protected]> wrote: >> >>> Yeah - there is something very weird with the ground on that Tandy. >>> Maybe some problematic traces? Or a bad IC leaking current to ground? >>> >>> Can you measure the DC power consumption? It should be ~60-70mA IIRC. >>> >>> On Wed, Dec 6, 2017 at 10:14 PM, Brian White <[email protected]> wrote: >>> > After watching a youtube video about how to use an oscilloscope by >>> sparkfun, >>> > I switched all probes and channels to 10x and adjusted the trim caps >>> in the >>> > probes against the built in test signal to make the square wave look >>> square. >>> > >>> > With gnd ref on the cpu gnd pin 20 instead of chassis gnd, and a couple >>> > probes on X1 and reset_in, and one probe on chassis ground, now the x1 >>> and >>> > reset_in signals are steady, reset_in looks flatter, and only the >>> trace for >>> > chassis ground floats and bobs up and down now. >>> > >>> > So chassis ground simply floats around in relation to the rest of the >>> board, >>> > or at least in relation to the cpu. Not a bad afe in the scope. >>> *chagrin* >>> > >>> > >>> > -- >>> > bkw >>> > >>> > On Dec 6, 2017 7:38 PM, "Brian White" <[email protected]> wrote: >>> >> >>> >> This is the bobbing I was talking about. It's dumb for me to even be >>> >> talking about it yet since I haven't even done a basic comparison >>> check on >>> >> some other reference yet. >>> >> >>> >> https://youtu.be/b9jAYsfTOzQ >>> <https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2Fb9jAYsfTOzQ&data=02%7C01%7C%7C33b7c3a9b7cd4909b28f08d53e64ed91%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636483525556528212&sdata=UvTz5UI2LRigb2jv0YVX%2BQqcwLR1LS1JpfYvVsiA3Ts%3D&reserved=0> >>> >> >>> >> And here's another look at a different signal hooked up a different >>> way. >>> >> Here, I have the ground ref hooked to the gnd pin 20 on the 8085, NOT >>> the >>> >> chassis ground. And CH4 is on pin 18, AD6. The offsets, trigger, and >>> >> vertical scales are all visible on-screen. >>> >> >>> >> https://photos.app.goo.gl/mel4CKym2EtcV1352 >>> <https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fphotos.app.goo.gl%2Fmel4CKym2EtcV1352&data=02%7C01%7C%7C33b7c3a9b7cd4909b28f08d53e64ed91%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636483525556528212&sdata=Z%2FNVGP3BjFaZW64aT0rMQteNAfXinZKhIC0XL6c%2BK%2Bk%3D&reserved=0> >>> >> >>> >> https://photos.app.goo.gl/K1AIj3Pmt15xXfR72 >>> <https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fphotos.app.goo.gl%2FK1AIj3Pmt15xXfR72&data=02%7C01%7C%7C33b7c3a9b7cd4909b28f08d53e64ed91%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636483525556528212&sdata=vX%2FNje%2BZK0f1cDmSAeohlNWJlD%2BZi1%2FHbUawQmBi0y8%3D&reserved=0> >>> >> >>> >> >>> >> -- >>> >> bkw >>> >> >>> > >>> >> >
