Radio Shack and/or Tandy Corporation vintage computer hardware and software.

Aug 162020
Tandy 6000 Power Supply Replacement

I bought this Tandy 6000 computer system back in 2013. It’s the last model in the Tandy/TRS-80 model II/12/16/6000 series. It would not power up, and I began an on-again/off-again project of fixing its power supply spanning over several years while being distracted by all sorts of other shiny objects. I ended up temporarily (?) replacing its power supply with a modern generic power supply in 2018. This is a summary of what I did, in case it might inspire other owners of the Tandy/Radio Shack business computer system line.

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Sep 182016
Wanted: Radio Shack Color TVs for TRS-80 Color Computer

My first computer was a Radio Shack TRS-80 Color Computer which my dad bought for Christmas in 1981. With a built-in RF modulator, it plugged into an antenna switch box mounted on the family color TV. That old Magnavox TV is long gone, but I still have that Color Computer.

A “holy grail” that I seek for my collection is one of the Radio Shack color televisions which were featured in advertisements for the Color Computer. There are two that I’m looking for.

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Aug 212014
Word Processing was Expensive in 1980!

In a recent eBay purchase that I made, the seller included a 1980 brochure advertising word processing capabilities of the TRS-80 Model I computer system. The advertised system prices ranged from $2,046.95 for a cassette-based system with a dot matrix printer, to $5492.95 for a system with two 80k floppy drives and a daisy wheel printer. Computers sure have gotten a lot cheaper since then!

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Jul 292014
TRS-80 Model 1

Well, I’m finally the proud new owner of a TRS-80 Model 1 system! I just bought it on eBay for the princely sum of $380.85 including shipping. Yes, I’m geeky enough to take pleasure in the presence of "8085" in that amount.

Here are the eBay listing pictures, used with permission from the seller. I’m looking forward to seeing it in person, because I haven’t touched one since around 1979 or so, and back then I didn’t know anything about computers. My first computer experience came with a TRS-80 Color Computer a year or two later, and I never got any experience with the Z-80 TRS-80s until I became interested in retrocomputing less than a year ago.

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Jul 062014
New Life for a TRS-80 TP-10 Printer

The little Radio Shack TRS-80 model TP-10 was a thermal printer with a serial interface, formerly sold for use with machines like the Color Computer. They show up on eBay from time to time, sometimes for very few dollars. They’re small and quiet, and suitable for utility printing such as when developing BASIC programs. You wouldn’t want to turn in a book report printed on one, but they’re fine for utility purposes. I got mine for next to nothing as a ride-along with some other items in an eBay lot. It had a bit of paper left in it, but the paper appears to have weathered a lot of hot summers in somebody’s garage, and it doesn’t give very good print quality any more.

Unfortunately, paper for the TP-10 isn’t so easy to find. They use 4-1/8" wide thermal roll paper, which doesn’t seem to be a common size in the US at this time. When original TP-10 paper shows up on eBay, it’s listed at $10 a roll or more… I think I paid about that much for the whole printer! I decided to try an experiment to see how easy it would be to cut down common (for the time being…) FAX machine paper.

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Nov 242013
Version 2 of TRS-80 Model 4 ROM Adapter

I previously designed a small adapter board to allow a regular 2764 EPROM to be plugged into a TRS-80 Model 4 (Gate Array version only) in place of ROM chip U4, in order to use the new auto-booting feature of the FreHD hard disk emulator. As I posted earlier, the assembled board was a bit too tall to fit under the aluminum shield that is present on US Model 4 computers, and it also needed a couple of pull-up resistors added. I changed my board design to address these problems.

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Oct 272013
M4-GA-ROM-BC: TRS-80 Model 4 (Gate Array Version) ROM B/C EPROM Adapter

Fred Vecoven has designed a neat hard disk drive emulator for the TRS-80 model I, III, 4, 4P and 4D computers, called "FreHD". That is pronounced “Fred”; the "H" is silent. Ian Mavric manufactures and sells them, and I ordered one from him recently via his eBay store. It works quite well.

Now they’ve come up with a cool new innovation: Modified ROMs for those computers which allow them to boot directly from the FreHD without needing a floppy drive, and even present an on-screen menu to allow the operator to select which image to mount! Different ROMs are needed for each model and production variant of the 8-bit TRS-80 machines. My Model 4 happens to be the so-called “gate array” version. It uses a 24-pin mask-programmed 8k x 8 ROM which is not pin-compatible with common 28-pin 2764 EPROMs. It’s not too hard to adapt a 2764 with a few soldered wires, but I’m really allergic to blue wires. So, I’ve designed a little board which should plug in to the ROM socket in place of the original ROM, and then accept both the original ROM and a 2764 EPROM, with a jumper to select one or the other.

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Oct 222013
CoCoEPROMpak: A PCB for EPROMs in the TRS-80 Color Computer Cartridge Port

I designed this printed circuit board (PCB) to allow regular 2732 through 27256 EPROM chips to be plugged into the cartridge expansion port of a TRS-80 Color Computer. My main motivation was to crank out a simple design to try out a prototype PCB vendor called OSH Park. Unlike most small-run, online-ordered PCB vendors, they provide boards with ENIG (gold plating) surface finish, which is much better than HASL (solder plating) for edge connectors.

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