I don't have any such handy source of ground within reach of the lead. You can't grab the vgnd pin on the chip with the alligator directly. The only 2 xtals within reach, one is insulated, and the other the can is not grounded.
However the frame of the DIR/ACP switch has continuity with the vgnd pin (but not ans/orig!), and so does one of the reachable legs on the cassette jack. Those are both reachable. So I'll use those instead of jumper leads to vgnd or other gnd further away. Here is, blue is CLK OUT, yellow is IO/M, triggering on IO/M so I can get that repeating pulse. Then, /RD, ALE, AD0, & AD2, with hold off set to 47.3ms, which stabilizes a repeating pattern on most pins. I wrote which pic is which pin in the comment on each. https://photos.app.goo.gl/vcTg4yUhvjXKBxeh1 This is on the bad unit. Just to be clear, I fully recognize that email is no way to go through the process of diagnosing something like this once the easy obvious stuff has been eliminated, especially when I don't really know what I'm doing and can't make good use of pointers. I'm not expecting anything more than the pointers you guys have already given me. I still have to work through what Steve said to look at. That's why these pics include /RD, ALE, and AD0. But those are at the cpu not at the memory chips. Also, I have other working units, so I'm only trying to puzzle this one out for the fun of it and to learn some things. Don't work harder on it than I am myself! With that in mind, thanks, this is kind of fun. :) -- bkw 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 >> >> >> > >> >
