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A few weeks earlier I have purchased an "as is" but working model 100 laptop. I've fixed some of the issues by soldering new capacitors for the screen, but the lines are still there. Would buying a lcd screen for TRS-80 model 102 work for the model 100?

Right now ebay doesn't have a lot of "as is" model 100s just 102s. Picture of my trs-80 model 100

enter image description here

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  • If you have specs or part numbers for the 102 screen I have a service manual for the 100 that I might be able to use for a comparison. Or if you find a service manual for the 102 we can see if the hardware is even schematically similar. It might be a way to built up a decent answer...
    – user12
    Feb 13, 2019 at 22:12
  • That all being said, the specs for the display between the two are the same. AFAIK, the difference between the two are ROM improvements, RAM increases, and surface mount technology. Even though they might be the same electrically, that latter point might make things incompatible. A service manual might clarify this. (Not an answer because of all my hand-waving.)
    – user12
    Feb 13, 2019 at 22:16
  • As an aside, can you provide a picture of the display problem you are having? I have a model 100 with a particular display issue. It might be good to see if it is the same symptoms.
    – user12
    Feb 16, 2019 at 16:59

2 Answers 2

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I fetched the Radio Shack Service Manual for the Model 100 (26-3801/3802) and the Tandy 102 Technical Reference Manual (26-252) and both discuss the LCD display timing details along with a driver schematic for each.

(All images snipped from PDF copies of the manuals listed above, both of which I grabbed from Club 100.)

So, let's compare Model 100 Fig. 4-14: Fig. 4-14

and Fig. 4-15: Fig. 4-15

with the Model 102 Figure 2-10: Figure 2-10

and Figure 2-11: Figure 2-11

In general, the LCD connector pin-outs look the same, as do the timing and signal descriptions. There are a few differences in how those pins are driven by the discrete components, but this might just be an artefact of how the schematics were drawn.

They look very similar, electronically, and appear to be pin-compatible. I'd want to stare hard at the driver circuitry details to make sure I understood the differences.

I think the differences in the driver circuits are not significant:

  • Either the Model 102 has an additional buffer between Y7 and pin 18 or the buffer is drawn in one case and not the other. But those should be the same, electrically.
  • Pin 19 looks identical to my eyes.
  • Pin 4 (the circuit for controlling the contrast it looks like) look equivalent to me, even if the part numbers have changed. The voltage divider resistors are the same values, anyway. There are missing capacitors (decouplers?) in the 102 schematic, but maybe those were deemed unnecessary (or C16 obviates them).

Maybe someone else here could tell us if any of that raises some red flags.

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  • As a noob, I'll start learning how to read the schematics. I'll find your answer useful!
    – Travis Wells
    Feb 18, 2019 at 15:24
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If you want to use a 102 display in a 100, you've got an annoying task ahead - While User12's answer shows that they are electrically the same, the connector is very different. The Model 100 has a 2 row connector with (I believe) .100 pin spacing. Similar to what you'd see on an old IDE drive.

The 102 has a flat ribbon that pushes into a connector on the PCB. I believe these are called 'Flat Flexible Cables'.

So, assuming that the LCD modules are electrically the same, to use a 102 module in a 100 means you have to hand wire one end of the connection. This is by no means undoable, it's just going to be annoying.

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    For reference, I think the FFC for the 102 is a Molex part - 15168-0375 (1.25mm pitch, 152mm long). I looked that up because I've damaged mine (had a pin peel off the cable during re-insertion) and I need a new one.
    – Michael Kohne
    Sep 6, 2020 at 0:49
  • More information: I ended up with 15168-0379 (same family, 202mm) because the shorter cable wasn't available in quantity 1. Turns out these cables are significantly thinner than the original. I ended up backing the ends with a bit of Kapton tape to make them fit securely in the connectors. Once I did so, they DO seem to work as replacements.
    – Michael Kohne
    Sep 14, 2020 at 23:48

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