Actually the reset is moving only at power on and when I press the reset button, otherwise it is stable. I tried to follow the reset signal after the Reset out of the CPU through couple of buffers but it is consistent and not cycling.
As LA I only have a Saleae 8 clone, but should do the job. I'll try the address and data lines as suggested. Any other signal of interest I should trace? Mauro Sent from my iPad On 15/dic/2017, at 01:12, Fugu ME100 <[email protected]> wrote: > What is the RESET line into the CPU doing during the loops? Is the RESET > stable? > > The CPU appears to be RESET, heads to the ROM for data but for some reason > fails to complete and RESETs itself. No activity on the RAM or LCD would > indicate the CPU is not completing the ROM boot. At this point I would > usually hang on my Logic Analyzer to see where the Address and Data lines are > heading. > > Have you checked out the Address Lines and Data Lines to make sure none are > stuck at either 0, 1 or some other state? They all should show some activity > during a RESET. > > From: M100 <[email protected]> on behalf of Mauro Pintus > <[email protected]> > Reply-To: <[email protected]> > Date: Thursday, December 14, 2017 at 3:55 PM > To: <[email protected]> > Subject: Re: [M100] diagnose > > Thank you Fugu and Brian for the feedback. > > Yes I tried the beep BASIC test with no luck and also the cold start (the M10 > and the M100 are almost identical...). > > I made few other measurements trying to replicate what Brian is doing and for > sure the unit is in a loop... > > In the linked google photo album I added another picture (the first one) > showing the ROM CS (Pin 20 yellow trace) and the IO/M of the main processor > (Pin 34 blue trace) > https://photos.app.goo.gl/8YSbaAxZBuXu5rjC2 > > As you can see at the beginning of the repeted sequence, I get only 5 pulses > on the IO/M > > The strange thing is that there is so little activity on the RAM CEx (chip > enable), like nothing is loaded. > > Finally I measured also the CSx (chip select) on the LCD connector and none > are moving, confirming that on the LCD nothing can be displayed. > > Mauro > > > > > On Dec 13, 2017, at 7:01 AM, Fugu ME100 wrote: > >> Vee at –4.9V is good. >> >> You may have already looked at these options, so apologies if you have… >> >> The repetitive nature of the ROM CS cycling could be the CPU in a software >> loop waiting for keyboard input. Have you tried the BEEP test from BASIC >> to see if the motherboard is actually running? >> >> Have you tried a cold start? On the M100 press ctrl+pause while powering >> on, not sure about the M10. It could be the memory is corrupted with the >> loss of backup power. Always a good idea when first powering after >> switching off/on the backup power.. >> >> >> From: M100 <[email protected]> on behalf of Mauro Pintus >> <[email protected]> >> Reply-To: <[email protected]> >> Date: Tuesday, December 12, 2017 at 5:24 PM >> To: <[email protected]> >> Subject: Re: [M100] diagnose >> >> 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 >>>>> >> >>>>> >> 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://photos.app.goo.gl/K1AIj3Pmt15xXfR72 >>>>> >> >>>>> >> >>>>> >> -- >>>>> >> bkw >>>>> >> >>>>> > >
