Re: [M100] Tandy Model 100
Hi The failure you describe is not one I have seen. The two LCDs that failed in my machines had horizontal bars of slightly darker contrast. When the contrast was varied the bars remained slightly darker than the rest of the screen. Eventually the -5V dropped to -2V as I assume the current draw exceeded the power supply limits. In both cases it appeared the horizontal driver chip was bad and could not properly drive the LCD or perhaps the LCD itself was bad. Hard to tell but replacing the LCD module with another one fixed the problem. The fact you need to power cycle the unit, not just press reset, could mean there is a power supply issue on the motherboard.As the contrast is changed the LCD driver chips might be seeing the supply voltages drop causing erratic behavior. May want to check that the cable to the screen is good and has no bad joints at the LCD module side? Could be a simple dry joint on the cable connection. On 14/10/18, 8:22 AM, "M100 on behalf of Rafael Arena" wrote: >Hi! > >Yeah, everything seems stable on the +-5v side. I will try to replace all >the caps. But probably the screen is going bad :( > >Thank you, > >> >> >> >>
Re: [M100] Tandy Model 100
Hi! Yeah, everything seems stable on the +-5v side. I will try to replace all the caps. But probably the screen is going bad :( Thank you, > On Oct 14, 2018, at 10:57 AM, Fugu ME100 wrote: > > Hi > > If the voltage change on pin 4 is smooth the voltages look right - pg 38 > of the M100 reference manual gives 0-4V as the range for V2. It feels > like VR1 is working correctly, indeed the whole contrast circuit would > appear to be fine. > > With the screen plugged in can you measure the -5V and +5V voltages at > their respective test points. They should remain stable as the contrast > is changed. Also check the reset line to the LCD, it is pin 7. > > It is quite tricky to test with the screen plugged in, the only way I have > been able to do that is to take the screen out to get at the connector > pins. > > Although it may appear good the -5V supply could still have problems due > to bad caps. Similarly the +5V could be bad too because of bad caps. It > sounds more like a power supply issue having to power cycle to make > things work properly. If one cap has been replaced I would probably just > replace all the power supply related caps. The 10uF caps always seem to > be dried up when I have had power supply issues. > > It could also just be a bad screen they do fail themselves due to age :( > > > On 14/10/18, 3:53 AM, "M100 on behalf of Rafael Arena" > > wrote: > >> Hi! >> >> I tried what was suggested and I get 0-3.8v on pin four (without the >> screen plugged in). Can’t seem to figure out how to measure pin 4 with >> the screen plugged in. When i turn the contrast knob the screen starts >> to jump around the display random line sporadically. I have to turn the >> computer on and off a few times in order to get it to come on. >> >> Thank you, >> >>> On Oct 12, 2018, at 11:57 AM, Fugu ME100 wrote: >>> >>> Hi >>> >>> The voltages look good. I usually replace C86 too it is part of the -5V >>> output circuit. >>> >>> You could try measuring the contrast voltage on the connector, pin 4, >>> see >>> if it smoothly transitions and there are no “jumps". Also check the -5V >>> is stable as you vary the contrast. I have noticed on some screens that >>> are failing the -5V will drop to -2V as the screen draws too much >>> current >>> as the contrast is varied. >>> >>> If the contrast voltage is not a smooth change then you could try >>> Brian’s >>> suggestion to clean VR1. >>> >>> Is it always missing a few lines on the screen? Do the missing lines >>> have >>> a pattern? >>> >>> On 12/10/18, 2:35 AM, "M100 on behalf of Rafael Arena" >>> >>> wrote: >>> Hi, At times the computer comes on and when adjusting the screen display the image gets all distorted and then fades away. I have checked the +5 and -5 volts that the screen needs and I get +5 and -4.8 volts respectively. I changed capaciitor ‘C85’ and checked all the memory chips. Like I said it works every now and again, missing a few lines on the screen. When i play with the contrast knob the image distorts and some times fades away. Any of this makes sense? Lol Thank you, > On Oct 11, 2018, at 10:27 PM, Fugu ME100 wrote: > > Hi > > What are the symptoms you are experiencing? > > VR1 could go bad but it could also be due to oxidation on the > resistors > tracks. People have tried to use contact cleaner to revive them. > Might > be worth looking into trying that option first? > > > On 11/10/18, 3:57 PM, "M100 on behalf of Rafael Arena" > minikni...@hotmail.com> > wrote: > >> Hello, >> >> I have a semi functional Model 100. I believe the issue is with the >> variable resistor ŒVR1¹. Where can I get a replacement? Do those >> VR¹s >> typically go bad? >> >> Thank you, > > >>> >>> > >
Re: [M100] Tandy Model 100
Hi If the voltage change on pin 4 is smooth the voltages look right - pg 38 of the M100 reference manual gives 0-4V as the range for V2. It feels like VR1 is working correctly, indeed the whole contrast circuit would appear to be fine. With the screen plugged in can you measure the -5V and +5V voltages at their respective test points. They should remain stable as the contrast is changed. Also check the reset line to the LCD, it is pin 7. It is quite tricky to test with the screen plugged in, the only way I have been able to do that is to take the screen out to get at the connector pins. Although it may appear good the -5V supply could still have problems due to bad caps. Similarly the +5V could be bad too because of bad caps. It sounds more like a power supply issue having to power cycle to make things work properly. If one cap has been replaced I would probably just replace all the power supply related caps. The 10uF caps always seem to be dried up when I have had power supply issues. It could also just be a bad screen they do fail themselves due to age :( On 14/10/18, 3:53 AM, "M100 on behalf of Rafael Arena" wrote: >Hi! > >I tried what was suggested and I get 0-3.8v on pin four (without the >screen plugged in). Can’t seem to figure out how to measure pin 4 with >the screen plugged in. When i turn the contrast knob the screen starts >to jump around the display random line sporadically. I have to turn the >computer on and off a few times in order to get it to come on. > >Thank you, > >> On Oct 12, 2018, at 11:57 AM, Fugu ME100 wrote: >> >> Hi >> >> The voltages look good. I usually replace C86 too it is part of the -5V >> output circuit. >> >> You could try measuring the contrast voltage on the connector, pin 4, >>see >> if it smoothly transitions and there are no “jumps". Also check the -5V >> is stable as you vary the contrast. I have noticed on some screens that >> are failing the -5V will drop to -2V as the screen draws too much >>current >> as the contrast is varied. >> >> If the contrast voltage is not a smooth change then you could try >>Brian’s >> suggestion to clean VR1. >> >> Is it always missing a few lines on the screen? Do the missing lines >>have >> a pattern? >> >> On 12/10/18, 2:35 AM, "M100 on behalf of Rafael Arena" >> >> wrote: >> >>> Hi, >>> >>> At times the computer comes on and when adjusting the screen display >>>the >>> image gets all distorted and then fades away. I have checked the +5 >>>and >>> -5 volts that the screen needs and I get +5 and -4.8 volts >>>respectively. >>> I changed capaciitor ‘C85’ and checked all the memory chips. Like I >>>said >>> it works every now and again, missing a few lines on the screen. When >>>i >>> play with the contrast knob the image distorts and some times fades >>>away. >>> Any of this makes sense? Lol >>> >>> Thank you, >>> On Oct 11, 2018, at 10:27 PM, Fugu ME100 wrote: Hi What are the symptoms you are experiencing? VR1 could go bad but it could also be due to oxidation on the resistors tracks. People have tried to use contact cleaner to revive them. Might be worth looking into trying that option first? On 11/10/18, 3:57 PM, "M100 on behalf of Rafael Arena" >>>minikni...@hotmail.com> wrote: > Hello, > > I have a semi functional Model 100. I believe the issue is with the > variable resistor ŒVR1¹. Where can I get a replacement? Do those >VR¹s > typically go bad? > > Thank you, >> >>
Re: [M100] Tandy Model 100
Hi! I tried what was suggested and I get 0-3.8v on pin four (without the screen plugged in). Can’t seem to figure out how to measure pin 4 with the screen plugged in. When i turn the contrast knob the screen starts to jump around the display random line sporadically. I have to turn the computer on and off a few times in order to get it to come on. Thank you, > On Oct 12, 2018, at 11:57 AM, Fugu ME100 wrote: > > Hi > > The voltages look good. I usually replace C86 too it is part of the -5V > output circuit. > > You could try measuring the contrast voltage on the connector, pin 4, see > if it smoothly transitions and there are no “jumps". Also check the -5V > is stable as you vary the contrast. I have noticed on some screens that > are failing the -5V will drop to -2V as the screen draws too much current > as the contrast is varied. > > If the contrast voltage is not a smooth change then you could try Brian’s > suggestion to clean VR1. > > Is it always missing a few lines on the screen? Do the missing lines have > a pattern? > > On 12/10/18, 2:35 AM, "M100 on behalf of Rafael Arena" > > wrote: > >> Hi, >> >> At times the computer comes on and when adjusting the screen display the >> image gets all distorted and then fades away. I have checked the +5 and >> -5 volts that the screen needs and I get +5 and -4.8 volts respectively. >> I changed capaciitor ‘C85’ and checked all the memory chips. Like I said >> it works every now and again, missing a few lines on the screen. When i >> play with the contrast knob the image distorts and some times fades away. >> Any of this makes sense? Lol >> >> Thank you, >> >>> On Oct 11, 2018, at 10:27 PM, Fugu ME100 wrote: >>> >>> Hi >>> >>> What are the symptoms you are experiencing? >>> >>> VR1 could go bad but it could also be due to oxidation on the resistors >>> tracks. People have tried to use contact cleaner to revive them. Might >>> be worth looking into trying that option first? >>> >>> >>> On 11/10/18, 3:57 PM, "M100 on behalf of Rafael Arena" >>> >>> wrote: >>> Hello, I have a semi functional Model 100. I believe the issue is with the variable resistor ŒVR1¹. Where can I get a replacement? Do those VR¹s typically go bad? Thank you, >>> >>> > >
Re: [M100] program library in WAV format
agreed thanks for all you do i am a new M100 owner On Sat, Oct 13, 2018 at 10:30 PM you got me wrote: > thank you for running this project. It makes it easier for some m100 > owners to grab and use software. Who knows, maybe it will help to grow the > m100 community. > -- > *From:* M100 on behalf of Jesus R < > sonor...@gmail.com> > *Sent:* Saturday, October 13, 2018 7:28 PM > *To:* m100@lists.bitchin100.com > *Subject:* [M100] program library in WAV format > > > Team, the programs in the Games, Drives, Utilities, Text, Programming, > Education, and Print tabs are up. > > new shorter link to archive:www.sonore.us/m100 > > Jesus R > >
