Re: [M100] In over my head? Or a Challenge!!
Well, I now have a fairly clean M100 PCB (using the glycerine and alcohol recipe), but no change on the LCD status (still not displaying on this unit though it works on my 8201a). More digging in my future. On Fri, Mar 26, 2021 at 6:40 PM Daryl Tester < dt-m...@handcraftedcomputers.com.au> wrote: > On 26/3/21 10:49 pm, Jeffrey Birt wrote: > > > Most people use Isopropyl Alcohol (IPA) I tend to use denatured alcohol > > (methylated spirits) as I can get it locally and inexpensively. Each > > type works a little better as a solvent on different types of things. > > I did see it referred to as IPA, but I'm with Jonathan on this - I > associate IPA with beer, which, given the context of using alcohol, > was confusing. :) > > On an unrelated note, does anyone want to buy a beer soaked M100? (j/k). > > Cheers, >--dt > -- -- Brad Grier
Re: [M100] In over my head? Or a Challenge!!
On 26/3/21 10:49 pm, Jeffrey Birt wrote: Most people use Isopropyl Alcohol (IPA) I tend to use denatured alcohol (methylated spirits) as I can get it locally and inexpensively. Each type works a little better as a solvent on different types of things. I did see it referred to as IPA, but I'm with Jonathan on this - I associate IPA with beer, which, given the context of using alcohol, was confusing. :) On an unrelated note, does anyone want to buy a beer soaked M100? (j/k). Cheers, --dt
Re: [M100] In over my head? Or a Challenge!!
Most people use Isopropyl Alcohol (IPA) I tend to use denatured alcohol (methylated spirits) as I can get it locally and inexpensively. Each type works a little better as a solvent on different types of things. Jeff Birt -Original Message- From: M100 On Behalf Of Daryl Tester Sent: Thursday, March 25, 2021 8:39 PM To: m...@bitchin100.com Subject: Re: [M100] In over my head? Or a Challenge!! On 24/3/21 11:49 pm, Jeffrey Birt wrote: > I suspect it would work by itself, but it will take a lot of it. I > have used alcohol followed by a typical flux/PCB cleaner product which > works (to save on the more expensive flux cleaner). A transcontinental question - what type of alcohol are y'all talking about here - isopropyl or something else? Cheers, --dt
Re: [M100] In over my head? Or a Challenge!!
Hello, Where I am, IPA is something I generally get at a pub... When there were pubs open. Though I suspect it is isopropyl alcohol in this post Sorry, been isolated too long.. Jonathan Ursprungligt meddelande Från : b...@bradgrier.com Datum : 2021-03-26 - 02:50 (CEST) Till : m...@bitchin100.com Ämne : Re: [M100] In over my head? Or a Challenge!! I've got some glycerine on my grocery list now and I've got IPA, so flux removal is in the near future. It's a quiet night so I think I'm going to test your PCR again Jeff ; maybe I missed something. On Thu, Mar 25, 2021 at 7:39 PM Daryl Tester < dt-m...@handcraftedcomputers.com.au> wrote: On 24/3/21 11:49 pm, Jeffrey Birt wrote: > I suspect it would work by itself, but it will take a lot of it. I have used > alcohol > followed by a typical flux/PCB cleaner product which works (to save on the > more > expensive flux cleaner). A transcontinental question - what type of alcohol are y'all talking about here - isopropyl or something else? Cheers, --dt -- -- Brad Grier
Re: [M100] In over my head? Or a Challenge!!
I've got some glycerine on my grocery list now and I've got IPA, so flux removal is in the near future. It's a quiet night so I think I'm going to test your PCR again Jeff ; maybe I missed something. On Thu, Mar 25, 2021 at 7:39 PM Daryl Tester < dt-m...@handcraftedcomputers.com.au> wrote: > On 24/3/21 11:49 pm, Jeffrey Birt wrote: > > > I suspect it would work by itself, but it will take a lot of it. I have > used alcohol > > followed by a typical flux/PCB cleaner product which works (to save on > the more > > expensive flux cleaner). > > A transcontinental question - what type of alcohol are y'all talking about > here - > isopropyl or something else? > > Cheers, >--dt > -- -- Brad Grier
Re: [M100] In over my head? Or a Challenge!!
On 24/3/21 11:49 pm, Jeffrey Birt wrote: I suspect it would work by itself, but it will take a lot of it. I have used alcohol followed by a typical flux/PCB cleaner product which works (to save on the more expensive flux cleaner). A transcontinental question - what type of alcohol are y'all talking about here - isopropyl or something else? Cheers, --dt
Re: [M100] In over my head? Or a Challenge!!
trap the rosin well and leave behind a nice clean board. They are good for cleaning up an individual spot like one footprint during re-work or repairs. -- bkw On Wed, Mar 24, 2021 at 8:52 AM Jeffrey Birt <mailto:bir...@soigeneris.com>> wrote: I was also reminded this morning, by another email, of the evils of the flux used on the M100. It can turn conductive and cause everything from the machine being stuck in reset, to power supply issues to fantom key presses. It is also a pain to clean off. I like to add about 10% glycerin to 90% alcohol (99% alcohol), paint it on the back of the PCB, wait 10 minutes and scrub it with a toothbrush, flush with alcohol and repeat. If you only have alcohol that will work too. I think the glycerin helps as it increases the viscosity enough to keep the alcohol in place. __ __ Jeff Birt __ __ *From:* M100 mailto:m100-boun...@lists.bitchin100.com>> *On Behalf Of *Brad Grier *Sent:* Tuesday, March 23, 2021 8:43 PM *To:* m...@bitchin100.com <mailto:m...@bitchin100.com> *Subject:* Re: [M100] In over my head? Or a Challenge!! __ __ Thanks Jeff! I just watched that video and it was *very* helpful. I may have gotten ahead of myself in the diagnosis so looking forward to putting some of your techniques to use. I'm thinking I can do most basic testing with my multimeter, but should probably look at getting a proper o-scope in the near future. Tempted by those cheap ones but they don't go into the 2mhz range :( __ __ Thanks again for your advice -- it's appreciated. __ __ --Brad __ __ On Tue, Mar 23, 2021 at 8:00 AM Jeffrey Birt mailto:bir...@soigeneris.com>> wrote: I did a video a while back about the first steps in troubleshooting a vintage computer. In a nutshell think ‘PCR’ Power, Clock, Reset. Make sure that all power supply rails are functional, then check that you have a good clock signal and finally check for a properly working reset. Without these 3 basic things nothing else will work and you can get confusing results. For example a reset that does not work properly can cause everything from not booting at all (held in reset) to the system coming up various random states as things were not properly reset. Jeff Birt *From:* M100 mailto:m100-boun...@lists.bitchin100.com>> *On Behalf Of *Brad Grier *Sent:* Monday, March 22, 2021 10:33 PM *To:* m100@lists.bitchin100.com <mailto:m100@lists.bitchin100.com> *Subject:* [M100] In over my head? Or a Challenge!! Hi everyone, as the subject line says, am I in over my head (for someone with old basic electronics knowledge), or is this a worthy challenge? [TL;DR] System symptoms: Won't power the screen, BASIC doesn't really work, unusual voltages on LCD connector pins. What to do? And why?? A few months ago I received a M100 that wasn't really working. Initial symptom is no display. I was looking at this as a learning experience -- to see if I could do some simple fixes and get it going again, and dust off my ancient basic electronics knowledge. I only have a multimeter, so I knew this could be a challenge. Initial testing revealed that it did power up and will 'Beep' on command (blindly entering Basic and typing Beep). LCD does work -- I connected it to my NEC PC-8201a and had a functioning display (with a tiny line of dead pixels in zone 1). So I'm ruling out a bad LCD. The mainboard looks fine. No obvious scratches or leaking battery or caps. No obviously damaged components. No staining of any kind other than the standard-issue coating of flux (which I've read can turn conductive so I'm open to cleaning all that off too). Display-related transistors and diodes (according to the troubleshooting flowchart) check out. The caps look great too -- but I haven't desoldered each of them to test them out of circuit. I've read recommendations to recap anyway, but I'm not sure it'd be worth it if the other problems aren't related to bad caps. Voltages on the LCD Connector pins seemed weird when compared with my NEC PC8201a. Image here: https://imgur.com/a/xfNIdF1 <https://imgur.com/a/xfNIdF1> Related to caps? Something else? The LCD is getting these voltages (the cable is fine). So now I'm thinking there might be something with the logic. So I tried typing a simple basic prog
Re: [M100] In over my head? Or a Challenge!!
I suspect it would work by itself, but it will take a lot of it. I have used alcohol followed by a typical flux/PCB cleaner product which works (to save on the more expensive flux cleaner). Jeff Birt From: M100 On Behalf Of Stephen Adolph Sent: Wednesday, March 24, 2021 8:10 AM To: m...@bitchin100.com Subject: Re: [M100] In over my head? Or a Challenge!! wrt cleaning the PCB, would a standard flux remover also work? On Wed, Mar 24, 2021 at 8:52 AM Jeffrey Birt mailto:bir...@soigeneris.com> > wrote: I was also reminded this morning, by another email, of the evils of the flux used on the M100. It can turn conductive and cause everything from the machine being stuck in reset, to power supply issues to fantom key presses. It is also a pain to clean off. I like to add about 10% glycerin to 90% alcohol (99% alcohol), paint it on the back of the PCB, wait 10 minutes and scrub it with a toothbrush, flush with alcohol and repeat. If you only have alcohol that will work too. I think the glycerin helps as it increases the viscosity enough to keep the alcohol in place. Jeff Birt From: M100 mailto:m100-boun...@lists.bitchin100.com> > On Behalf Of Brad Grier Sent: Tuesday, March 23, 2021 8:43 PM To: m...@bitchin100.com <mailto:m...@bitchin100.com> Subject: Re: [M100] In over my head? Or a Challenge!! Thanks Jeff! I just watched that video and it was *very* helpful. I may have gotten ahead of myself in the diagnosis so looking forward to putting some of your techniques to use. I'm thinking I can do most basic testing with my multimeter, but should probably look at getting a proper o-scope in the near future. Tempted by those cheap ones but they don't go into the 2mhz range :( Thanks again for your advice -- it's appreciated. --Brad On Tue, Mar 23, 2021 at 8:00 AM Jeffrey Birt mailto:bir...@soigeneris.com> > wrote: I did a video a while back about the first steps in troubleshooting a vintage computer. In a nutshell think ‘PCR’ Power, Clock, Reset. Make sure that all power supply rails are functional, then check that you have a good clock signal and finally check for a properly working reset. Without these 3 basic things nothing else will work and you can get confusing results. For example a reset that does not work properly can cause everything from not booting at all (held in reset) to the system coming up various random states as things were not properly reset. Jeff Birt From: M100 mailto:m100-boun...@lists.bitchin100.com> > On Behalf Of Brad Grier Sent: Monday, March 22, 2021 10:33 PM To: m100@lists.bitchin100.com <mailto:m100@lists.bitchin100.com> Subject: [M100] In over my head? Or a Challenge!! Hi everyone, as the subject line says, am I in over my head (for someone with old basic electronics knowledge), or is this a worthy challenge? [TL;DR] System symptoms: Won't power the screen, BASIC doesn't really work, unusual voltages on LCD connector pins. What to do? And why?? A few months ago I received a M100 that wasn't really working. Initial symptom is no display. I was looking at this as a learning experience -- to see if I could do some simple fixes and get it going again, and dust off my ancient basic electronics knowledge. I only have a multimeter, so I knew this could be a challenge. Initial testing revealed that it did power up and will 'Beep' on command (blindly entering Basic and typing Beep). LCD does work -- I connected it to my NEC PC-8201a and had a functioning display (with a tiny line of dead pixels in zone 1). So I'm ruling out a bad LCD. The mainboard looks fine. No obvious scratches or leaking battery or caps. No obviously damaged components. No staining of any kind other than the standard-issue coating of flux (which I've read can turn conductive so I'm open to cleaning all that off too). Display-related transistors and diodes (according to the troubleshooting flowchart) check out. The caps look great too -- but I haven't desoldered each of them to test them out of circuit. I've read recommendations to recap anyway, but I'm not sure it'd be worth it if the other problems aren't related to bad caps. Voltages on the LCD Connector pins seemed weird when compared with my NEC PC8201a. Image here: <https://imgur.com/a/xfNIdF1> https://imgur.com/a/xfNIdF1 Related to caps? Something else? The LCD is getting these voltages (the cable is fine). So now I'm thinking there might be something with the logic. So I tried typing a simple basic program, blindly, but it's a short program so I'm pretty sure I got it in properly: 10 beep 20 goto 10 Nothing. No string of beeps. And after that, a simple beep won't work either. But, power cycle or reset, enter basic, type beep, it works. beep:beep:beep also works. Now I'm thinking partially bad RAM? Or RAM select logic? So, two issues (display and BASIC), or is this all a case of a bunc
Re: [M100] In over my head? Or a Challenge!!
wrt cleaning the PCB, would a standard flux remover also work? [image: image.png] On Wed, Mar 24, 2021 at 8:52 AM Jeffrey Birt wrote: > I was also reminded this morning, by another email, of the evils of the > flux used on the M100. It can turn conductive and cause everything from the > machine being stuck in reset, to power supply issues to fantom key presses. > It is also a pain to clean off. I like to add about 10% glycerin to 90% > alcohol (99% alcohol), paint it on the back of the PCB, wait 10 minutes and > scrub it with a toothbrush, flush with alcohol and repeat. If you only have > alcohol that will work too. I think the glycerin helps as it increases the > viscosity enough to keep the alcohol in place. > > > > Jeff Birt > > > > *From:* M100 *On Behalf Of *Brad Grier > *Sent:* Tuesday, March 23, 2021 8:43 PM > *To:* m...@bitchin100.com > *Subject:* Re: [M100] In over my head? Or a Challenge!! > > > > Thanks Jeff! I just watched that video and it was *very* helpful. I may > have gotten ahead of myself in the diagnosis so looking forward to putting > some of your techniques to use. I'm thinking I can do most basic testing > with my multimeter, but should probably look at getting a proper o-scope in > the near future. Tempted by those cheap ones but they don't go into the > 2mhz range :( > > > > Thanks again for your advice -- it's appreciated. > > > > --Brad > > > > On Tue, Mar 23, 2021 at 8:00 AM Jeffrey Birt > wrote: > > I did a video a while back about the first steps in troubleshooting a > vintage computer. In a nutshell think ‘PCR’ Power, Clock, Reset. Make sure > that all power supply rails are functional, then check that you have a good > clock signal and finally check for a properly working reset. Without these > 3 basic things nothing else will work and you can get confusing results. > For example a reset that does not work properly can cause everything from > not booting at all (held in reset) to the system coming up various random > states as things were not properly reset. > > Jeff Birt > > > > *From:* M100 *On Behalf Of *Brad Grier > *Sent:* Monday, March 22, 2021 10:33 PM > *To:* m100@lists.bitchin100.com > *Subject:* [M100] In over my head? Or a Challenge!! > > > > Hi everyone, as the subject line says, am I in over my head (for someone > with old basic electronics knowledge), or is this a worthy challenge? > > [TL;DR] System symptoms: Won't power the screen, BASIC doesn't really > work, unusual voltages on LCD connector pins. What to do? And why?? > > > > A few months ago I received a M100 that wasn't really working. Initial > symptom is no display. I was looking at this as a learning experience -- to > see if I could do some simple fixes and get it going again, and dust off my > ancient basic electronics knowledge. I only have a multimeter, so I knew > this could be a challenge. > > > > Initial testing revealed that it did power up and will 'Beep' on command > (blindly entering Basic and typing Beep). > > > > LCD does work -- I connected it to my NEC PC-8201a and had a functioning > display (with a tiny line of dead pixels in zone 1). So I'm ruling out a > bad LCD. > > > > The mainboard looks fine. No obvious scratches or leaking battery or caps. > No obviously damaged components. No staining of any kind other than the > standard-issue coating of flux (which I've read can turn conductive so I'm > open to cleaning all that off too). > > > > Display-related transistors and diodes (according to the troubleshooting > flowchart) check out. The caps look great too -- but I haven't desoldered > each of them to test them out of circuit. I've read recommendations to > recap anyway, but I'm not sure it'd be worth it if the other problems > aren't related to bad caps. > > > > Voltages on the LCD Connector pins seemed weird when compared with my NEC > PC8201a. Image here: https://imgur.com/a/xfNIdF1 > Related to caps? Something else? The LCD is getting these voltages (the > cable is fine). > > > > So now I'm thinking there might be something with the logic. So I tried > typing a simple basic program, blindly, but it's a short program so I'm > pretty sure I got it in properly: > 10 beep > > 20 goto 10 > > > > Nothing. No string of beeps. > > And after that, a simple beep won't work either. > > > > But, power cycle or reset, enter basic, type beep, it works. > > beep:beep:beep also works. Now I'm thinking partially bad RAM? Or RAM > select logic? > > > > So, two issues (display and BASIC), or is this all a case of a bunch of > invisibly bad caps and I should just bite the bullet, desolder a few and > test them. > > > > Thoughts? Ideas? What am I missing? Is this thing destined for a parts > computer or could it be a good challenge to heal it up? All advice > appreciated :) > > > > --Brad > > > > > > > > > > > > > > > > > > > > > > -- > > -- > Brad Grier > > > > > > > > > -- > > -- > Brad Grier > > > > >
Re: [M100] In over my head? Or a Challenge!!
I was also reminded this morning, by another email, of the evils of the flux used on the M100. It can turn conductive and cause everything from the machine being stuck in reset, to power supply issues to fantom key presses. It is also a pain to clean off. I like to add about 10% glycerin to 90% alcohol (99% alcohol), paint it on the back of the PCB, wait 10 minutes and scrub it with a toothbrush, flush with alcohol and repeat. If you only have alcohol that will work too. I think the glycerin helps as it increases the viscosity enough to keep the alcohol in place. Jeff Birt From: M100 On Behalf Of Brad Grier Sent: Tuesday, March 23, 2021 8:43 PM To: m...@bitchin100.com Subject: Re: [M100] In over my head? Or a Challenge!! Thanks Jeff! I just watched that video and it was *very* helpful. I may have gotten ahead of myself in the diagnosis so looking forward to putting some of your techniques to use. I'm thinking I can do most basic testing with my multimeter, but should probably look at getting a proper o-scope in the near future. Tempted by those cheap ones but they don't go into the 2mhz range :( Thanks again for your advice -- it's appreciated. --Brad On Tue, Mar 23, 2021 at 8:00 AM Jeffrey Birt mailto:bir...@soigeneris.com> > wrote: I did a video a while back about the first steps in troubleshooting a vintage computer. In a nutshell think ‘PCR’ Power, Clock, Reset. Make sure that all power supply rails are functional, then check that you have a good clock signal and finally check for a properly working reset. Without these 3 basic things nothing else will work and you can get confusing results. For example a reset that does not work properly can cause everything from not booting at all (held in reset) to the system coming up various random states as things were not properly reset. Jeff Birt From: M100 mailto:m100-boun...@lists.bitchin100.com> > On Behalf Of Brad Grier Sent: Monday, March 22, 2021 10:33 PM To: m100@lists.bitchin100.com <mailto:m100@lists.bitchin100.com> Subject: [M100] In over my head? Or a Challenge!! Hi everyone, as the subject line says, am I in over my head (for someone with old basic electronics knowledge), or is this a worthy challenge? [TL;DR] System symptoms: Won't power the screen, BASIC doesn't really work, unusual voltages on LCD connector pins. What to do? And why?? A few months ago I received a M100 that wasn't really working. Initial symptom is no display. I was looking at this as a learning experience -- to see if I could do some simple fixes and get it going again, and dust off my ancient basic electronics knowledge. I only have a multimeter, so I knew this could be a challenge. Initial testing revealed that it did power up and will 'Beep' on command (blindly entering Basic and typing Beep). LCD does work -- I connected it to my NEC PC-8201a and had a functioning display (with a tiny line of dead pixels in zone 1). So I'm ruling out a bad LCD. The mainboard looks fine. No obvious scratches or leaking battery or caps. No obviously damaged components. No staining of any kind other than the standard-issue coating of flux (which I've read can turn conductive so I'm open to cleaning all that off too). Display-related transistors and diodes (according to the troubleshooting flowchart) check out. The caps look great too -- but I haven't desoldered each of them to test them out of circuit. I've read recommendations to recap anyway, but I'm not sure it'd be worth it if the other problems aren't related to bad caps. Voltages on the LCD Connector pins seemed weird when compared with my NEC PC8201a. Image here: <https://imgur.com/a/xfNIdF1> https://imgur.com/a/xfNIdF1 Related to caps? Something else? The LCD is getting these voltages (the cable is fine). So now I'm thinking there might be something with the logic. So I tried typing a simple basic program, blindly, but it's a short program so I'm pretty sure I got it in properly: 10 beep 20 goto 10 Nothing. No string of beeps. And after that, a simple beep won't work either. But, power cycle or reset, enter basic, type beep, it works. beep:beep:beep also works. Now I'm thinking partially bad RAM? Or RAM select logic? So, two issues (display and BASIC), or is this all a case of a bunch of invisibly bad caps and I should just bite the bullet, desolder a few and test them. Thoughts? Ideas? What am I missing? Is this thing destined for a parts computer or could it be a good challenge to heal it up? All advice appreciated :) --Brad -- -- Brad Grier -- -- Brad Grier
Re: [M100] In over my head? Or a Challenge!!
Thanks Jeff! I just watched that video and it was *very* helpful. I may have gotten ahead of myself in the diagnosis so looking forward to putting some of your techniques to use. I'm thinking I can do most basic testing with my multimeter, but should probably look at getting a proper o-scope in the near future. Tempted by those cheap ones but they don't go into the 2mhz range :( Thanks again for your advice -- it's appreciated. --Brad On Tue, Mar 23, 2021 at 8:00 AM Jeffrey Birt wrote: > I did a video a while back about the first steps in troubleshooting a > vintage computer. In a nutshell think ‘PCR’ Power, Clock, Reset. Make sure > that all power supply rails are functional, then check that you have a good > clock signal and finally check for a properly working reset. Without these > 3 basic things nothing else will work and you can get confusing results. > For example a reset that does not work properly can cause everything from > not booting at all (held in reset) to the system coming up various random > states as things were not properly reset. > > Jeff Birt > > > > *From:* M100 *On Behalf Of *Brad Grier > *Sent:* Monday, March 22, 2021 10:33 PM > *To:* m100@lists.bitchin100.com > *Subject:* [M100] In over my head? Or a Challenge!! > > > > Hi everyone, as the subject line says, am I in over my head (for someone > with old basic electronics knowledge), or is this a worthy challenge? > > [TL;DR] System symptoms: Won't power the screen, BASIC doesn't really > work, unusual voltages on LCD connector pins. What to do? And why?? > > > > A few months ago I received a M100 that wasn't really working. Initial > symptom is no display. I was looking at this as a learning experience -- to > see if I could do some simple fixes and get it going again, and dust off my > ancient basic electronics knowledge. I only have a multimeter, so I knew > this could be a challenge. > > > > Initial testing revealed that it did power up and will 'Beep' on command > (blindly entering Basic and typing Beep). > > > > LCD does work -- I connected it to my NEC PC-8201a and had a functioning > display (with a tiny line of dead pixels in zone 1). So I'm ruling out a > bad LCD. > > > > The mainboard looks fine. No obvious scratches or leaking battery or caps. > No obviously damaged components. No staining of any kind other than the > standard-issue coating of flux (which I've read can turn conductive so I'm > open to cleaning all that off too). > > > > Display-related transistors and diodes (according to the troubleshooting > flowchart) check out. The caps look great too -- but I haven't desoldered > each of them to test them out of circuit. I've read recommendations to > recap anyway, but I'm not sure it'd be worth it if the other problems > aren't related to bad caps. > > > > Voltages on the LCD Connector pins seemed weird when compared with my NEC > PC8201a. Image here: https://imgur.com/a/xfNIdF1 > Related to caps? Something else? The LCD is getting these voltages (the > cable is fine). > > > > So now I'm thinking there might be something with the logic. So I tried > typing a simple basic program, blindly, but it's a short program so I'm > pretty sure I got it in properly: > 10 beep > > 20 goto 10 > > > > Nothing. No string of beeps. > > And after that, a simple beep won't work either. > > > > But, power cycle or reset, enter basic, type beep, it works. > > beep:beep:beep also works. Now I'm thinking partially bad RAM? Or RAM > select logic? > > > > So, two issues (display and BASIC), or is this all a case of a bunch of > invisibly bad caps and I should just bite the bullet, desolder a few and > test them. > > > > Thoughts? Ideas? What am I missing? Is this thing destined for a parts > computer or could it be a good challenge to heal it up? All advice > appreciated :) > > > > --Brad > > > > > > > > > > > > > > > > > > > > > > -- > > -- > Brad Grier > > > > > -- -- Brad Grier
Re: [M100] In over my head? Or a Challenge!!
I did a video a while back about the first steps in troubleshooting a vintage computer. In a nutshell think ‘PCR’ Power, Clock, Reset. Make sure that all power supply rails are functional, then check that you have a good clock signal and finally check for a properly working reset. Without these 3 basic things nothing else will work and you can get confusing results. For example a reset that does not work properly can cause everything from not booting at all (held in reset) to the system coming up various random states as things were not properly reset. Jeff Birt From: M100 On Behalf Of Brad Grier Sent: Monday, March 22, 2021 10:33 PM To: m100@lists.bitchin100.com Subject: [M100] In over my head? Or a Challenge!! Hi everyone, as the subject line says, am I in over my head (for someone with old basic electronics knowledge), or is this a worthy challenge? [TL;DR] System symptoms: Won't power the screen, BASIC doesn't really work, unusual voltages on LCD connector pins. What to do? And why?? A few months ago I received a M100 that wasn't really working. Initial symptom is no display. I was looking at this as a learning experience -- to see if I could do some simple fixes and get it going again, and dust off my ancient basic electronics knowledge. I only have a multimeter, so I knew this could be a challenge. Initial testing revealed that it did power up and will 'Beep' on command (blindly entering Basic and typing Beep). LCD does work -- I connected it to my NEC PC-8201a and had a functioning display (with a tiny line of dead pixels in zone 1). So I'm ruling out a bad LCD. The mainboard looks fine. No obvious scratches or leaking battery or caps. No obviously damaged components. No staining of any kind other than the standard-issue coating of flux (which I've read can turn conductive so I'm open to cleaning all that off too). Display-related transistors and diodes (according to the troubleshooting flowchart) check out. The caps look great too -- but I haven't desoldered each of them to test them out of circuit. I've read recommendations to recap anyway, but I'm not sure it'd be worth it if the other problems aren't related to bad caps. Voltages on the LCD Connector pins seemed weird when compared with my NEC PC8201a. Image here: <https://imgur.com/a/xfNIdF1> https://imgur.com/a/xfNIdF1 Related to caps? Something else? The LCD is getting these voltages (the cable is fine). So now I'm thinking there might be something with the logic. So I tried typing a simple basic program, blindly, but it's a short program so I'm pretty sure I got it in properly: 10 beep 20 goto 10 Nothing. No string of beeps. And after that, a simple beep won't work either. But, power cycle or reset, enter basic, type beep, it works. beep:beep:beep also works. Now I'm thinking partially bad RAM? Or RAM select logic? So, two issues (display and BASIC), or is this all a case of a bunch of invisibly bad caps and I should just bite the bullet, desolder a few and test them. Thoughts? Ideas? What am I missing? Is this thing destined for a parts computer or could it be a good challenge to heal it up? All advice appreciated :) --Brad -- -- Brad Grier
Re: [M100] In over my head? Or a Challenge!!
Hi John, thanks for getting back to me. I *think* that was one of the early steps I tried. I've since removed the memory battery (a few weeks ago -- it was crusty) so it's not a concern right now. But, I figured what the heck, and just did the recovery test outlined in your link, and sadly had no response on the display. If I listen carefully, I can hear the relay engage, but other than that, no response from the system. The system can be made to beep by entering Basic and typing beep, but trying to create a simple program doesn't work. And then there's the odd connector power readings. Thoughts? --Brad On Mon, Mar 22, 2021 at 11:14 PM John R. Hogerhuis wrote: > Hello Brad, before you start doing surgery, you didn't say if you've done > the usual recovery procedures. > > > http://bitchin100.com/wiki/index.php?title=Recovering_an_Unresponsive_Laptop > > -- John. > -- -- Brad Grier
Re: [M100] In over my head? Or a Challenge!!
Hello Brad, before you start doing surgery, you didn't say if you've done the usual recovery procedures. http://bitchin100.com/wiki/index.php?title=Recovering_an_Unresponsive_Laptop -- John.
[M100] In over my head? Or a Challenge!!
Hi everyone, as the subject line says, am I in over my head (for someone with old basic electronics knowledge), or is this a worthy challenge? [TL;DR] System symptoms: Won't power the screen, BASIC doesn't really work, unusual voltages on LCD connector pins. What to do? And why?? A few months ago I received a M100 that wasn't really working. Initial symptom is no display. I was looking at this as a learning experience -- to see if I could do some simple fixes and get it going again, and dust off my ancient basic electronics knowledge. I only have a multimeter, so I knew this could be a challenge. Initial testing revealed that it did power up and will 'Beep' on command (blindly entering Basic and typing Beep). LCD does work -- I connected it to my NEC PC-8201a and had a functioning display (with a tiny line of dead pixels in zone 1). So I'm ruling out a bad LCD. The mainboard looks fine. No obvious scratches or leaking battery or caps. No obviously damaged components. No staining of any kind other than the standard-issue coating of flux (which I've read can turn conductive so I'm open to cleaning all that off too). Display-related transistors and diodes (according to the troubleshooting flowchart) check out. The caps look great too -- but I haven't desoldered each of them to test them out of circuit. I've read recommendations to recap anyway, but I'm not sure it'd be worth it if the other problems aren't related to bad caps. Voltages on the LCD Connector pins seemed weird when compared with my NEC PC8201a. Image here: https://imgur.com/a/xfNIdF1 Related to caps? Something else? The LCD is getting these voltages (the cable is fine). So now I'm thinking there might be something with the logic. So I tried typing a simple basic program, blindly, but it's a short program so I'm pretty sure I got it in properly: 10 beep 20 goto 10 Nothing. No string of beeps. And after that, a simple beep won't work either. But, power cycle or reset, enter basic, type beep, it works. beep:beep:beep also works. Now I'm thinking partially bad RAM? Or RAM select logic? So, two issues (display and BASIC), or is this all a case of a bunch of invisibly bad caps and I should just bite the bullet, desolder a few and test them. Thoughts? Ideas? What am I missing? Is this thing destined for a parts computer or could it be a good challenge to heal it up? All advice appreciated :) --Brad -- -- Brad Grier
