If you're convinced it's stuck in a loop, removing all power (including the NiCd) for a time should fix that....
On 12/14/17, Mauro Pintus <[email protected]> wrote: > 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 >>> >> >>> > >> > >
