Re: [M100] Have a question about my M100
On 17/5/19 11:52 pm, Ed Graffius wrote: btw - the , 'B''E'E'P' works, so that means the CPU is CPUing? This means you've entered BASIC, and executed the direct command BEEP, which means the CPU thinks its CPUing (which I guess is the point of the exercise. :-)) (and down the existential rabbit hole we go). Cheers, Daryl.
Re: [M100] Have a question about my M100
5.1V - Original Message - From: Ed Graffius To: m...@bitchin100.com Sent: Friday, May 17, 2019 11:24 AM Subject: Re: [M100] Have a question about my M100 just in case D14 is bad anyone got the spec on the zener? I cannot read it clearly off the SCM. I got a few 4.5 and a ton of 5.2 in stock... -Original Message- From: Josh Malone To: m100 Sent: Fri, May 17, 2019 11:10 am Subject: Re: [M100] Have a question about my M100 Service manual specifies Vee failure as indicating components D15, C85, and D14. On my most recent Vee failure, C85 was leaking and D14 was physically broken. On Fri, May 17, 2019 at 11:06 AM Stephen Adolph wrote: > > probably the capacitor on the -5V rails is a problem here. fix -5V and you will get a display again almost certainly. > > If +5V is working then the switching supply itself is functioning. > > I have machines with this symptom also, if a fix is identified please share.I have never recapped an M100 . Maybe I should be. > > > On Fri, May 17, 2019 at 10:32 AM Josh Malone wrote: >> >> On Fri, May 17, 2019 at 10:22 AM Ed Graffius wrote: >> > >> > ok, opened it up and the nicad has 4.8ish volts on it. >> >> Good. I'd plan to remove or replace it soon anyway. >> >> > Theory: lack of -5v prevents the LCD from lighting up? >> >> Yep. Check out the M100 service manual >> (https://ftp.whtech.com/club100/doc/m100ServiceManual.pdf) for >> troubleshooting steps on the power supply. It's a great reference. >> >> > >> > btw - the , 'B''E'E'P' works, so that means the CPU is CPUing? >> >> Yep. Display issues only. Should be a simple fix. Congrats on your acquisition. >> >> -Josh
Re: [M100] Have a question about my M100
NO, I did not replace the tantalums. Typically, they ‘popcorn’ when bad and if there are no trouble symptoms, I don’t replace them as a matter of course. You will see a wrist strap in some of my other videos. I’m in the habit touching ground on a regular basis and don’t shuffle or jump around quickly so I’ve never had an issue with ESD (as an adult). But I do try to set a good example. I’ve been thinking about moving my grounding jack for the strap to the front/underside of the table to keep the silly strap from being draped all over my work. Arcade shopper has new memory modules in stock and memory batteries. I used a supercap in the video, which works, but does not last as long as a new NiMh cell. Arcadeshopper carries the batteries and I have them on my website too. Jeff Birt (Hey_Birt) From: M100 On Behalf Of Ed Graffius Sent: Friday, May 17, 2019 10:23 AM To: m...@bitchin100.com Subject: Re: [M100] Have a question about my M100 Hey Birt! lol, I am watching your video nowdid you replace any of the 'tants? I know that as they age they break down such that they introduce stray rfi...for the low uF NPs, did you try any films? (and there is a lot of CMOS in there so where is your ESD strap!!! (old IBM habits die hard ;-)) thanks again, I have most of the parts in stock from my stereo restoration hobby - silicon and ECs so I will get to this as soon as I carve out some block time. excited to see it run. btw - has base memory onlyany leads on NOS or manufactured memory for it? -Original Message- From: Jeffrey Birt mailto:bir...@soigeneris.com> > To: m100 mailto:m...@bitchin100.com> > Sent: Fri, May 17, 2019 11:04 am Subject: Re: [M100] Have a question about my M100 Ed, Corrosion is a sure sign of leaking electrolytic caps. I did a video on a recap, link below. In the description is a link to a PDF with a color-coded capacitor map and part numbers for replacement caps from Mouser. https://youtu.be/IGTdNMx1V1w Jeff_Birt (Hey Birt!) From: M100 mailto:m100-boun...@lists.bitchin100.com> > On Behalf Of Ed Graffius Sent: Friday, May 17, 2019 9:22 AM To: m...@bitchin100.com <mailto:m...@bitchin100.com> Subject: Re: [M100] Have a question about my M100 thanks guysI have not used a listserv in decades so forgive..lol ok, opened it up and the nicad has 4.8ish volts on it. got a 6v PS and batteries in, have contrast wheel middle of the road and memory switch is on. I probed R127 and the collector of T21 and got 122Khz oscillation. Sound reasonable? I probed VDD and get 5.something volts. VEE gives me -.7v which is slightly less than the spec of -5v, this is all with respect to the transformer output ground. D15 (1S2076) appears to be badly corroded and Vf is 1.9v (all other glass silicon is in the .521-.560 range which I expect. I think this negates the efforts of zener D14. Theory: lack of -5v prevents the LCD from lighting up? so I was gonna tear it further apart and replace ALL the 1S2076 (35v, 450ma, 250mw) with either 1N914 or 1N4148 (much superior) - I dont think I have to Vf match any of them? btw - the , 'B''E'E'P' works, so that means the CPU is CPUing? -Original Message- From: Josh Malone mailto:josh.mal...@gmail.com> > To: m100 mailto:m...@bitchin100.com> > Sent: Fri, May 17, 2019 9:49 am Subject: Re: [M100] Have a question about my M100 On Fri, May 17, 2019 at 9:44 AM Stephen Adolph mailto:twospru...@gmail.com> > wrote: > > power on, > hit enter > type BEEP then enter > > if you hear a beep, your machine is running. Maybe with no display. I'd suggest opening it up pronto and removing that memory battery. Just snip it out if you don't feel like soldering. If it's completely dead, it can drag down the voltage rail to the RAM and cause system failure. This often presents as having to let your memory battery charge overnight (provide system power via DC or batteries, switch memory power on and wait) before it will boot. If you remove the memory NiCd entirely you eliminate this potential problem. Plus, it needs to come out, anyway. (https://twitter.com/48kRAM/status/1082807102714904576) -Josh
Re: [M100] Have a question about my M100
just in case D14 is bad anyone got the spec on the zener? I cannot read it clearly off the SCM. I got a few 4.5 and a ton of 5.2 in stock... -Original Message- From: Josh Malone To: m100 Sent: Fri, May 17, 2019 11:10 am Subject: Re: [M100] Have a question about my M100 Service manual specifies Vee failure as indicating components D15, C85, and D14. On my most recent Vee failure, C85 was leaking and D14 was physically broken. On Fri, May 17, 2019 at 11:06 AM Stephen Adolph wrote: > > probably the capacitor on the -5V rails is a problem here. fix -5V and you > will get a display again almost certainly. > > If +5V is working then the switching supply itself is functioning. > > I have machines with this symptom also, if a fix is identified please share. > I have never recapped an M100 . Maybe I should be. > > > On Fri, May 17, 2019 at 10:32 AM Josh Malone wrote: >> >> On Fri, May 17, 2019 at 10:22 AM Ed Graffius wrote: >> > >> > ok, opened it up and the nicad has 4.8ish volts on it. >> >> Good. I'd plan to remove or replace it soon anyway. >> >> > Theory: lack of -5v prevents the LCD from lighting up? >> >> Yep. Check out the M100 service manual >> (https://ftp.whtech.com/club100/doc/m100ServiceManual.pdf) for >> troubleshooting steps on the power supply. It's a great reference. >> >> > >> > btw - the , 'B''E'E'P' works, so that means the CPU is >> > CPUing? >> >> Yep. Display issues only. Should be a simple fix. Congrats on your >> acquisition. >> >> -Josh
Re: [M100] Have a question about my M100
Hey Birt! lol, I am watching your video nowdid you replace any of the
'tants? I know that as they age they break down such that they introduce stray
rfi...for the low uF NPs, did you try any films?
(and there is a lot of CMOS in there so where is your ESD strap!!! (old IBM
habits die hard ;-))
thanks again, I have most of the parts in stock from my stereo restoration
hobby - silicon and ECs so I will get to this as soon as I carve out some block
time. excited to see it run.
btw - has base memory onlyany leads on NOS or manufactured memory for it?
-Original Message-
From: Jeffrey Birt
To: m100
Sent: Fri, May 17, 2019 11:04 am
Subject: Re: [M100] Have a question about my M100
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{} #yiv8338382717 Ed, Corrosion is a sure sign of leaking electrolytic caps. I
did a video on a recap, link below. In the description is a link to a PDF with
a color-coded capacitor map and part numbers for replacement caps from Mouser.
https://youtu.be/IGTdNMx1V1w Jeff_Birt (Hey Birt!) From: M100
On Behalf Of Ed Graffius
Sent: Friday, May 17, 2019 9:22 AM
To: m...@bitchin100.com
Subject: Re: [M100] Have a question about my M100 thanks guysI have not
used a listserv in decades so forgive..lol ok, opened it up and the nicad has
4.8ish volts on it. got a 6v PS and batteries in, have contrast wheel middle
of the road and memory switch is on. I probed R127 and the collector of T21
and got 122Khz oscillation. Sound reasonable? I probed VDD and get
5.something volts. VEE gives me -.7v which is slightly less than the spec of
-5v, this is all with respect to the transformer output ground. D15 (1S2076)
appears to be badly corroded and Vf is 1.9v (all other glass silicon is in the
.521-.560 range which I expect. I think this negates the efforts of zener D14.
Theory: lack of -5v prevents the LCD from lighting up? so I was gonna tear
it further apart and replace ALL the 1S2076 (35v, 450ma, 250mw) with either
1N914 or 1N4148 (much superior) - I dont think I have to Vf match any of them?
btw - the , 'B''E'E'P' works, so that means the CPU is CPUing?
-Original Message-
From: Josh Malone
To: m100
Sent: Fri, May 17, 2019 9:49 am
Subject: Re: [M100] Have a question about my M100On Fri, May 17, 2019 at 9:44
AM Stephen Adolph wrote:
>
> power on,
> hit enter
> type BEEP then enter
>
> if you hear a beep, your machine is running. Maybe with no display.
I'd suggest opening it up pronto and removing that memory battery.
Just snip it out if you don't feel like soldering. If it's completely
dead, it can drag down the voltage rail to the RAM and cause system
failure. This often presents as having to let your memory battery
charge overnight (provide system power via DC or batteries, switch
memory power on and wait) before it will boot. If you remove the
memory NiCd entirely you eliminate this potential problem. Plus, it
needs to come out, anyway.
(https://twitter.com/48kRAM/status/1082807102714904576)
-Josh
Re: [M100] Have a question about my M100
Service manual specifies Vee failure as indicating components D15, C85, and D14. On my most recent Vee failure, C85 was leaking and D14 was physically broken. On Fri, May 17, 2019 at 11:06 AM Stephen Adolph wrote: > > probably the capacitor on the -5V rails is a problem here. fix -5V and you > will get a display again almost certainly. > > If +5V is working then the switching supply itself is functioning. > > I have machines with this symptom also, if a fix is identified please share. > I have never recapped an M100 . Maybe I should be. > > > On Fri, May 17, 2019 at 10:32 AM Josh Malone wrote: >> >> On Fri, May 17, 2019 at 10:22 AM Ed Graffius wrote: >> > >> > ok, opened it up and the nicad has 4.8ish volts on it. >> >> Good. I'd plan to remove or replace it soon anyway. >> >> > Theory: lack of -5v prevents the LCD from lighting up? >> >> Yep. Check out the M100 service manual >> (https://ftp.whtech.com/club100/doc/m100ServiceManual.pdf) for >> troubleshooting steps on the power supply. It's a great reference. >> >> > >> > btw - the , 'B''E'E'P' works, so that means the CPU is >> > CPUing? >> >> Yep. Display issues only. Should be a simple fix. Congrats on your >> acquisition. >> >> -Josh
Re: [M100] Have a question about my M100
You're right. Sorry - I thought the copy on club100 was the "good one" but I can't find it anywhere. I'm uploading a good copy to the Internet Archive now but it's transferring terribly slowly. :( -Josh On Fri, May 17, 2019 at 10:56 AM Ed Graffius wrote: > > Is there a better scan of the SCM portion of the SM? I blow it up to 250% > and I sort of infer which component is which by looking at the PCB and > matching closely with the SCM - the lettering is blurred. IT seems the SM > exists in many places on the web, but it appears to be the same scan. No > chance someone has an original? > > Also, it appears the main board is at least dual planar, meaning each > component has pads on BOTH sides. yikes, I gotta sharpen up one of my pencil > tips > > > > -Original Message- > From: Josh Malone > To: m100 > Sent: Fri, May 17, 2019 10:32 am > Subject: Re: [M100] Have a question about my M100 > > On Fri, May 17, 2019 at 10:22 AM Ed Graffius wrote: > > > > ok, opened it up and the nicad has 4.8ish volts on it. > > Good. I'd plan to remove or replace it soon anyway. > > > Theory: lack of -5v prevents the LCD from lighting up? > > Yep. Check out the M100 service manual > (https://ftp.whtech.com/club100/doc/m100ServiceManual.pdf) for > troubleshooting steps on the power supply. It's a great reference. > > > > > btw - the , 'B''E'E'P' works, so that means the CPU is > > CPUing? > > Yep. Display issues only. Should be a simple fix. Congrats on your > acquisition. > > > -Josh
Re: [M100] Have a question about my M100
probably the capacitor on the -5V rails is a problem here. fix -5V and you will get a display again almost certainly. If +5V is working then the switching supply itself is functioning. I have machines with this symptom also, if a fix is identified please share.I have never recapped an M100 . Maybe I should be. On Fri, May 17, 2019 at 10:32 AM Josh Malone wrote: > On Fri, May 17, 2019 at 10:22 AM Ed Graffius wrote: > > > > ok, opened it up and the nicad has 4.8ish volts on it. > > Good. I'd plan to remove or replace it soon anyway. > > > Theory: lack of -5v prevents the LCD from lighting up? > > Yep. Check out the M100 service manual > (https://ftp.whtech.com/club100/doc/m100ServiceManual.pdf) for > troubleshooting steps on the power supply. It's a great reference. > > > > > btw - the , 'B''E'E'P' works, so that means the CPU is > CPUing? > > Yep. Display issues only. Should be a simple fix. Congrats on your > acquisition. > > -Josh >
Re: [M100] Have a question about my M100
Ed, Corrosion is a sure sign of leaking electrolytic caps. I did a video on a recap, link below. In the description is a link to a PDF with a color-coded capacitor map and part numbers for replacement caps from Mouser. https://youtu.be/IGTdNMx1V1w Jeff_Birt (Hey Birt!) From: M100 On Behalf Of Ed Graffius Sent: Friday, May 17, 2019 9:22 AM To: m...@bitchin100.com Subject: Re: [M100] Have a question about my M100 thanks guysI have not used a listserv in decades so forgive..lol ok, opened it up and the nicad has 4.8ish volts on it. got a 6v PS and batteries in, have contrast wheel middle of the road and memory switch is on. I probed R127 and the collector of T21 and got 122Khz oscillation. Sound reasonable? I probed VDD and get 5.something volts. VEE gives me -.7v which is slightly less than the spec of -5v, this is all with respect to the transformer output ground. D15 (1S2076) appears to be badly corroded and Vf is 1.9v (all other glass silicon is in the .521-.560 range which I expect. I think this negates the efforts of zener D14. Theory: lack of -5v prevents the LCD from lighting up? so I was gonna tear it further apart and replace ALL the 1S2076 (35v, 450ma, 250mw) with either 1N914 or 1N4148 (much superior) - I dont think I have to Vf match any of them? btw - the , 'B''E'E'P' works, so that means the CPU is CPUing? -Original Message- From: Josh Malone mailto:josh.mal...@gmail.com> > To: m100 mailto:m...@bitchin100.com> > Sent: Fri, May 17, 2019 9:49 am Subject: Re: [M100] Have a question about my M100 On Fri, May 17, 2019 at 9:44 AM Stephen Adolph mailto:twospru...@gmail.com> > wrote: > > power on, > hit enter > type BEEP then enter > > if you hear a beep, your machine is running. Maybe with no display. I'd suggest opening it up pronto and removing that memory battery. Just snip it out if you don't feel like soldering. If it's completely dead, it can drag down the voltage rail to the RAM and cause system failure. This often presents as having to let your memory battery charge overnight (provide system power via DC or batteries, switch memory power on and wait) before it will boot. If you remove the memory NiCd entirely you eliminate this potential problem. Plus, it needs to come out, anyway. (https://twitter.com/48kRAM/status/1082807102714904576) -Josh
Re: [M100] Have a question about my M100
Is there a better scan of the SCM portion of the SM? I blow it up to 250% and I sort of infer which component is which by looking at the PCB and matching closely with the SCM - the lettering is blurred. IT seems the SM exists in many places on the web, but it appears to be the same scan. No chance someone has an original? Also, it appears the main board is at least dual planar, meaning each component has pads on BOTH sides. yikes, I gotta sharpen up one of my pencil tips -Original Message- From: Josh Malone To: m100 Sent: Fri, May 17, 2019 10:32 am Subject: Re: [M100] Have a question about my M100 On Fri, May 17, 2019 at 10:22 AM Ed Graffius wrote: > > ok, opened it up and the nicad has 4.8ish volts on it. Good. I'd plan to remove or replace it soon anyway. > Theory: lack of -5v prevents the LCD from lighting up? Yep. Check out the M100 service manual (https://ftp.whtech.com/club100/doc/m100ServiceManual.pdf) for troubleshooting steps on the power supply. It's a great reference. > > btw - the , 'B''E'E'P' works, so that means the CPU is CPUing? Yep. Display issues only. Should be a simple fix. Congrats on your acquisition. -Josh
Re: [M100] Have a question about my M100
On Fri, May 17, 2019 at 10:22 AM Ed Graffius wrote: > > ok, opened it up and the nicad has 4.8ish volts on it. Good. I'd plan to remove or replace it soon anyway. > Theory: lack of -5v prevents the LCD from lighting up? Yep. Check out the M100 service manual (https://ftp.whtech.com/club100/doc/m100ServiceManual.pdf) for troubleshooting steps on the power supply. It's a great reference. > > btw - the , 'B''E'E'P' works, so that means the CPU is CPUing? Yep. Display issues only. Should be a simple fix. Congrats on your acquisition. -Josh
Re: [M100] Have a question about my M100
thanks guysI have not used a listserv in decades so forgive..lol ok, opened it up and the nicad has 4.8ish volts on it. got a 6v PS and batteries in, have contrast wheel middle of the road and memory switch is on. I probed R127 and the collector of T21 and got 122Khz oscillation. Sound reasonable? I probed VDD and get 5.something volts. VEE gives me -.7v which is slightly less than the spec of -5v, this is all with respect to the transformer output ground. D15 (1S2076) appears to be badly corroded and Vf is 1.9v (all other glass silicon is in the .521-.560 range which I expect. I think this negates the efforts of zener D14. Theory: lack of -5v prevents the LCD from lighting up? so I was gonna tear it further apart and replace ALL the 1S2076 (35v, 450ma, 250mw) with either 1N914 or 1N4148 (much superior) - I dont think I have to Vf match any of them? btw - the , 'B''E'E'P' works, so that means the CPU is CPUing? -Original Message- From: Josh Malone To: m100 Sent: Fri, May 17, 2019 9:49 am Subject: Re: [M100] Have a question about my M100 On Fri, May 17, 2019 at 9:44 AM Stephen Adolph wrote: > > power on, > hit enter > type BEEP then enter > > if you hear a beep, your machine is running. Maybe with no display. I'd suggest opening it up pronto and removing that memory battery. Just snip it out if you don't feel like soldering. If it's completely dead, it can drag down the voltage rail to the RAM and cause system failure. This often presents as having to let your memory battery charge overnight (provide system power via DC or batteries, switch memory power on and wait) before it will boot. If you remove the memory NiCd entirely you eliminate this potential problem. Plus, it needs to come out, anyway. (https://twitter.com/48kRAM/status/1082807102714904576) -Josh
Re: [M100] Have a question about my M100
Make sure the memory power switch is ON. Then, you’ll need to do a hard reset, I think the ley combination is holding down control-shift and then pressing the reset button. Hopefully someone else will chime in if that is wrong. Jeff_Birt From: M100 On Behalf Of Ed Graffius Sent: Friday, May 17, 2019 8:26 AM To: m100@lists.bitchin100.com Subject: [M100] Have a question about my M100 I just picked one up last monday at an estate sale. New, in the box, but opened. lack of ANY fingerprints, wear etc leads me to believe got it, looked at it, lost interest fast. I put in 4 new AA batteries...no joy. I have the new manual, and I found the service manual online and poured thru it. So here we go: TRS80 M100 serial 306005812 Have not opened it yet. I would assume the nicad is long dead and is likely 'reaction complete' meaning it has no chance of charging. I did not get the power supply (nor was I looking for one at the auction, but part 2 is this monday so I will) I have ample power supplies I can rig up. I note it says tip negative - common to RS equipment - whereas the rest of the planet preferred tip positive. But again, I can dream up the correct polarity. I suspect due to age and perhaps accidental power reversal, the oscillator used to produce the board +/- DC could be faulty, and I have the proper tools to probe it and test it. >From looking at the SCM, if it was reversed polarity, small chance this >translates to the chipset as the PS/battery box is isolated thru the >transformer and reversal would have reverse biased the transistors. perhaps >dried caps on the timing circuit? dunno yet. When I turn if off, for a small half second the low batt light flashes, but that light is driven from a narrow voltage divider and would be expected. A couple times on power on if I press many keys, I get beeps from keys. faulty virgin display? Any ideas where to start? thanks!
Re: [M100] Have a question about my M100
power on, hit enter type BEEP then enter if you hear a beep, your machine is running. Maybe with no display. On Fri, May 17, 2019 at 9:41 AM Kevin Becker wrote: > I believe it is CTRL-BREAK-RESET. Also to state the obvious, try > adjusting the contrast control on the screen. > > > On May 17, 2019, at 9:38 AM, Jeffrey Birt wrote: > > Make sure the memory power switch is ON. Then, you’ll need to do a hard > reset, I think the ley combination is holding down control-shift and then > pressing the reset button. Hopefully someone else will chime in if that is > wrong. > > Jeff_Birt > > > *From:* M100 *On Behalf Of *Ed > Graffius > *Sent:* Friday, May 17, 2019 8:26 AM > *To:* m100@lists.bitchin100.com > *Subject:* [M100] Have a question about my M100 > > I just picked one up last monday at an estate sale. New, in the box, but > opened. lack of ANY fingerprints, wear etc leads me to believe got it, > looked at it, lost interest fast. > > I put in 4 new AA batteries...no joy. I have the new manual, and I found > the service manual online and poured thru it. > > So here we go: TRS80 M100 serial 306005812 > > Have not opened it yet. > > I would assume the nicad is long dead and is likely 'reaction complete' > meaning it has no chance of charging. I did not get the power supply (nor > was I looking for one at the auction, but part 2 is this monday so I will) > > I have ample power supplies I can rig up. > > I note it says tip negative - common to RS equipment - whereas the rest of > the planet preferred tip positive. But again, I can dream up the correct > polarity. > > I suspect due to age and perhaps accidental power reversal, the oscillator > used to produce the board +/- DC could be faulty, and I have the proper > tools to probe it and test it. > > From looking at the SCM, if it was reversed polarity, small chance this > translates to the chipset as the PS/battery box is isolated thru the > transformer and reversal would have reverse biased the transistors. > perhaps dried caps on the timing circuit? dunno yet. > > When I turn if off, for a small half second the low batt light flashes, > but that light is driven from a narrow voltage divider and would be > expected. A couple times on power on if I press many keys, I get beeps > from keys. faulty virgin display? > > Any ideas where to start? > > thanks! > > >
Re: [M100] Have a question about my M100
On Fri, May 17, 2019 at 9:44 AM Stephen Adolph wrote: > > power on, > hit enter > type BEEP then enter > > if you hear a beep, your machine is running. Maybe with no display. I'd suggest opening it up pronto and removing that memory battery. Just snip it out if you don't feel like soldering. If it's completely dead, it can drag down the voltage rail to the RAM and cause system failure. This often presents as having to let your memory battery charge overnight (provide system power via DC or batteries, switch memory power on and wait) before it will boot. If you remove the memory NiCd entirely you eliminate this potential problem. Plus, it needs to come out, anyway. (https://twitter.com/48kRAM/status/1082807102714904576) -Josh
Re: [M100] Have a question about my M100
I believe it is CTRL-BREAK-RESET. Also to state the obvious, try adjusting the contrast control on the screen. > On May 17, 2019, at 9:38 AM, Jeffrey Birt wrote: > > Make sure the memory power switch is ON. Then, you’ll need to do a hard > reset, I think the ley combination is holding down control-shift and then > pressing the reset button. Hopefully someone else will chime in if that is > wrong. > > Jeff_Birt > > > From: M100 <mailto:m100-boun...@lists.bitchin100.com>> On Behalf Of Ed Graffius > Sent: Friday, May 17, 2019 8:26 AM > To: m100@lists.bitchin100.com <mailto:m100@lists.bitchin100.com> > Subject: [M100] Have a question about my M100 > > I just picked one up last monday at an estate sale. New, in the box, but > opened. lack of ANY fingerprints, wear etc leads me to believe got it, > looked at it, lost interest fast. > > I put in 4 new AA batteries...no joy. I have the new manual, and I found the > service manual online and poured thru it. > > So here we go: TRS80 M100 serial 306005812 > > Have not opened it yet. > > I would assume the nicad is long dead and is likely 'reaction complete' > meaning it has no chance of charging. I did not get the power supply (nor > was I looking for one at the auction, but part 2 is this monday so I will) > > I have ample power supplies I can rig up. > > I note it says tip negative - common to RS equipment - whereas the rest of > the planet preferred tip positive. But again, I can dream up the correct > polarity. > > I suspect due to age and perhaps accidental power reversal, the oscillator > used to produce the board +/- DC could be faulty, and I have the proper tools > to probe it and test it. > > From looking at the SCM, if it was reversed polarity, small chance this > translates to the chipset as the PS/battery box is isolated thru the > transformer and reversal would have reverse biased the transistors. perhaps > dried caps on the timing circuit? dunno yet. > > When I turn if off, for a small half second the low batt light flashes, but > that light is driven from a narrow voltage divider and would be expected. A > couple times on power on if I press many keys, I get beeps from keys. faulty > virgin display? > > Any ideas where to start? > > thanks!
[M100] Have a question about my M100
I just picked one up last monday at an estate sale. New, in the box, but opened. lack of ANY fingerprints, wear etc leads me to believe got it, looked at it, lost interest fast. I put in 4 new AA batteries...no joy. I have the new manual, and I found the service manual online and poured thru it. So here we go: TRS80 M100 serial 306005812 Have not opened it yet. I would assume the nicad is long dead and is likely 'reaction complete' meaning it has no chance of charging. I did not get the power supply (nor was I looking for one at the auction, but part 2 is this monday so I will) I have ample power supplies I can rig up. I note it says tip negative - common to RS equipment - whereas the rest of the planet preferred tip positive. But again, I can dream up the correct polarity. I suspect due to age and perhaps accidental power reversal, the oscillator used to produce the board +/- DC could be faulty, and I have the proper tools to probe it and test it. >From looking at the SCM, if it was reversed polarity, small chance this >translates to the chipset as the PS/battery box is isolated thru the >transformer and reversal would have reverse biased the transistors. perhaps >dried caps on the timing circuit? dunno yet. When I turn if off, for a small half second the low batt light flashes, but that light is driven from a narrow voltage divider and would be expected. A couple times on power on if I press many keys, I get beeps from keys. faulty virgin display? Any ideas where to start? thanks!
