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Digital VT 102 Terminals
  by Bill Degnan - 07/30/2012 19:03
Digital VT 102
Digital VT-102 Terminal


Picked up 4 of these, I will make one working unit, sell/donate the rest.

More Pics

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VT-102 Cleaning and Testing
  by Bill Degnan - 08/12/2012 22:21
Here's one of the VT-102's after a thorough cleaning and testing.


I cleaned the externally-facing surfaces thoroughly, was not too bad. Three of the four VT-102's work, the other one seems to have a bad power supply.

Keyboards
One of the keyboards is complete and fully functional. One has a few missing keys and a bad "V" post which causes the key to sit too closely to the key above, causing it to not lift back into the ready position fully. As a result, a steady stream of "vvvvv..." is written to the screen. If you can work with a few missing keys and the V key removed, the keyboard works fine.

The third keyboard has numerous dead spots and as missing keys. I don't have a fourth keyboard for the last VT-102.

Note the filthy keyboard in the background. Magic Eraser does wonders to remove grunge from plastics.


Note about cleaning filthy computers. First of all, I don't accept computers with evidence excessive rust, animal urine or nesting inside, or heavy mold. I usually follow a three-step process. First I use a dry brush or rag to remove the surface dirt. Next I clean with a mild soap and water. Often I will remove the chassis entirely to wash in a utility sink. Lastly I clean the surfaces with Mr. Clean Magic Eraser (plastic) or Windex (glass/stainless steel).

Screenshot of the keyboard testing in local mode. To access local mode, hit the Set-Up key on the keyboard and hit the number 4.


One thing I noticed about the three working terminals was that the text size was taller on the tops of the screen compared to the bottom. This was the case for all three. I assume that there is a potentiometer that controls the display variables to adjust and correct this, it just seemed strange to me that all three had the same exact display characteristic. The barrel effect created by the camera lens exaggerates the text height difference, see photo above, but it's pretty evident.

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VT-102 Terminal capacitors
  by Bill Degnan - 08/13/2012 09:11
I got this message in response to my post:

"I think the difference in text size is that there is a capacitor messing up
causing the vertical sync to change as it's drawing the screen. I've had 2
Commodore monitors do the something similar (picture had vertical gaps at the
top and slowly closed going down, causing text to get smaller) and was told it
was a bad cap near the voltage regulators because of the heat."

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Adjusting VT102 Display Characteristics
  by Bill Degnan - 08/15/2012 15:00
The video power board of the VT-102 terminal. There are for adjustment pots to control display characteristics. The bottom one adjusts "linearity". A small adjustment was made.


This picture shows the text size after the linearity potentiometer adjustment. The top and bottom screen text is now the same size. It is likely that there has been some video capacitor decay since the terminal was assembled, but only a small adjustment was needed.



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Repairing dead vt102
  by Bill Degnan - 09/19/2012 07:39

I still have the one vt102 that does not boot, plus a vt103 with similar symptoms.

When I return to this project, here is a useful thread with repair info.

http://www.vintage-compu...2-something-blown/page3

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