Really appreciate your effort!!! I'll try to measure the suggested signals and get out my bag of GOOD caps :)
Mauro Inviato da iPhone > Il giorno Dec 15, 2017, alle ore 01:55, Fugu ME100 <[email protected]> ha > scritto: > > It would be interesting to see if the Address Lines fail at a specific > address all the time. Might give a clue as to what is causing the issue. In > the old days it was possible to watch the address lines walk through a count > sequence if you had a bad ROM or RAM. Although this one appears to keep > retrying something. > > Monitor them at the ROM pins if you can that way it will test the CPU to ROM > buffers. > > On the Electrolytic caps I always assume they are dead - either dried out or > leaked out ….. and yes as a matter of course I just replace them all, I have > bags of all the ones used on the M100 and T102s. I also have a big bag of > removed caps LOL. It takes me about 1-2hours to do a complete replacement > of caps, if they come out cleanly. However your voltages seem to be pretty > good and the CPU is booting. Usually if the +5V or –5V is off spec the caps > are bad or if the LCD screen is modulating then the –5V is bad. At least > that is my experience of the M100/T102. I just had to replace the power caps > on a PC8201A with a bad LCD screen now it looks good – so it is a common > issue regardless of the manufacturer. > > From: M100 <[email protected]> on behalf of Mauro Pintus > <[email protected]> > Reply-To: <[email protected]> > Date: Thursday, December 14, 2017 at 4:31 PM > To: "[email protected]" <[email protected]> > Subject: Re: [M100] diagnose > > 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 >>>>>> >> >>>>>> > >>> >>
