A while ago I received a NEC PC-8201 (a Japanese sibling of the Radio Shack / Tandy TRS-80 Model 100) with a very touchy LCD contrast control (the contrast adjustment dial). After recording a video of the issue, I pinged the good folk on the Slabtop Computers Discord channel about it. The consensus was that it had issues, and it’s not uncommon for the contrast control to be bad after 40 years.
And a warning — there were no drop-in replacement contrast controls available. They were obsolete.
After a search, it seemed this was true. I couldn’t find a pin-accurate drop-in replacement for the LCD contrast control – the VR1 potentiometer as designated by the Radio Shack / Tandy Model 100 technical documentation.
But there were many other thumb-wheel pot designs at all the online shops. And after a bit of thinking, and a bit of tinkering with the 3d printer, I found something that would work.
And it did. Initially I was a bit worried it was a LCD circuitry problem, but switching out the contrast control did the job. Here’s the video of the Drop-In VR1 replacement in action.
Another member of the Model T Computers: TRS-80 Model 100/200, NEC PC-8201/8300, Olivetti M10 etc Facebook group thought some kits would be a good idea — and it seemed like a good idea. So here they are.
Each unit is hand assembled from available components as well as a custom designed 3d printed tray and Wheel Lid assembled to bring it all together.
Each Drop-In VR1 kit is assembled and mailed from Canada — and costs $20.00 CAD plus postage.