Designing Custom LCDs To Repair Retrocomputers

China, we’re told, can make anything. If you need some PCBs in a few weeks, there are a few factories in China that will do it. If you need a nuclear reactor, yep, there’s probably a factory in China that’ll do it because nuclear reactors are listed as one of the items facing new tariffs when imported into the United States. No, I am not kidding. What about LCDs? What about old-school character LCDs? Is it possible to find a factory in China that will make you the LCD you want? That’s what [Robert Baruch] will find out, because he’s repairing an old computer with new parts.

The object of this repair and restomod is a TRS-80 Pocket Computer (PC-1), otherwise known as the Sharp PC-1211. It looks like a calculator, but no, it’s a legitimate computer you can program in BASIC. [Robert] bought this computer for a bit more than $5 on eBay ‘for repair’, which means the zinc-air battery was dead, and unfortunately, the LCD was shot. The LCD technically works, but it just doesn’t look good. Sometime in the last thirty years, moisture got in between the layers of glass, polarizing film, and liquid crystal. This is not unique to [Robert]’s unit — a lot of these PC-1s have the same problem, many of these broken seals rendering the computers themselves useless.

This is an ancient computer, and replacements for this LCD are impossible to find, but because the Sharp PC-1211 is well documented, it is possible to find the datasheet for the original display. With that, it’s just a question of finding an LCD manufacturer that will do it. So far, the costs look good — $800 USD ($300 for tooling and 10 samples, $500 for another 200 LCDs) is what it’ll take to get a few units. [Robert] already has a few people interested in repairing their own Pocket Computers. You can follow the eevblog thread here, or check out the video below.

24 thoughts on “Designing Custom LCDs To Repair Retrocomputers

  1. Nice job. I don’t have one of these machines, but if i had, i’d be interested. I do appreciate the effort though.

    I’m looking forward to hear how everything goes. Good luck!

  2. I had one of the Sharp models when I was in college. I used the heck out of it. It’s probably in a box in my hall closet. I wonder if mine still works. Be back in a while…

  3. Found it. Mine is a EL-5500II. Battery’s long dead but no visible damage. It takes common coin cell batteries.
    What I remember about it was that it had roughly the same capabilities as the Altair I had access to in High School. 4K of RAM. BASIC in ROM.

    The display on my model is shorter and it has buttons for scientific calculator functions It’s not exactly the same.

  4. What I want to know is, related to old lcds, where does one get a large effectively single pixel display to make blackout windows? I’ve looked everywhere to no avail. Nice fix by the way!!

    1. The problem with doing this is that it is only 50% transparent when “clear” due to the polarisors
      The only off-the-shelf.devices like this are the shutters used for welding helmets. Other shapes are possible but only as custom builds

  5. Dave on EEVBlog had an episode or two on making custom LCDs for his project, it was quite interesting, before that I thought it was not possible to make custom LCDs in relatively small quantities, but China comes to rescue again it seems.

  6. The PC-1 was my first computer — it’s what I learned BASIC on. Then I had a Color Computer 1 (CoCo). But I used my PC-1 through high school, until one day my backpack slid off my desk, and the PC-1 wound up sandwiched between the floor and a bunch of heavy textbooks, smashing the screen. That was a sad day.

  7. How much to put together an ExpressCard adapter with a pair of USB Type C ports? My not so old Dell laptop already has a bunch of USB 3.x ports, and an ExpressCard slot.

    It shouldn’t be at all difficult to design since ExpressCard has PCI Express x1 and there’s a ton of PCI Express x1 USB Type C cards available for desktops. Should merely be a matter of form factor.

    So WTH hasn’t anyone made them!? There are ExpressCards with two USB 3.x ports that fit flush, take one of those designs and modify as needed to swap in a USB C controller and connectors. No cheaping out simply grafting C ports onto a 3.x design because it won’t work properly.

    Why? Because many Type C devices flat out do not work correctly, or at all, with C to 3.x adapter dongles. I have a USB 3.x hub that plugs into a USB C port. I tried a C to 3 adapter and it’s not recognized *at all* connected to USB 3 ports. But if I plug it into a USB 2 port it works as a USB 2 hub.

    Just one of the many reasons for ExpressCard USB C to exist ASAP.

  8. The type 675 cells are not necessary zinc-air. It is the size normally also known as LR44 or AG13. I am not even sure, if zinc air cells were common or available in the days the calculator was built.
    I don’t see zinc-air cells as suitable for a calculator. It has a very low and discontinuous power consumption and a normal alkaline cells would last for a year or longer. A zinc air cell is dead latest after one week, independent if it is depleted or not.

    1. Orgininally these units were powered with 4 x 1.35V MR44 battery cells. Unfortunately, “M” here stands for Mercury, and these cells are no longer in production. The reason people use zinc-air batteries in their PC1211s now is that they have the same voltage and form factor. However the zinc-air batteries will decay on the shelf once you remove the cover, even when not in use, which is not optimal for your vintage computer collection :-) .

      The AG13, LR44 and similar cells also have the same form factor, last longer, but have a higher voltage (1.5V), you can use them in a PC1211 at your own risk (seems to work tho). You can even get voltage converters where you insert somewhat smaller 1.5V cells and get an output voltage of 1.35 V with the exact form factor of the vintage MR44, I guess that’s useful if you have really precious vintage equipment where the exact voltage matters (perhaps for vintage cameras, for correct exposure metering).

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