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" <m100-boun...@lists.bitchin100.com on behalf of minikni...@hotmail.com> 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 <b4me...@hotmail.com> 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" >> <m100-boun...@lists.bitchin100.com on behalf of 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, >> >>
