Bit-banging a BASIC Birthday

As dodgy as the early Tandy stuff's reputation was as "TRASH-80s", it's no surprise that OP's dad loved them. Back in the day, Tandy machines really did deliver value for money. Of course once you popped them open, their manufacturing-design issues would be revealed. There were bodgewires all over the place because of last-minute issues found after the PCBs had gone to manufacturing. And the ones with built-in CRTs had issues wherein the cathode of the CRT was DANGEROUSLY CLOSE to the main PCB. If you weren't careful cracking that puppy open -- zappo! Fried motherboard, possibly fried you!

For these reasons, and possibly also to hide their shame and embarrassment and make extra scratch on service calls, Tandy equipment often had one of those "Warranty void if seal is broken" stickers on it, which are now illegal to enforce even in the USA. They also used to seal the screwholes with Glyptal to prevent unauthorized tinkering; this so incensed my dad that he called all the way up the chain to the president of Tandy Corp. to make them stop (and also drilled through the Glyptal to get at the screws).

But when it worked, it was solid, not to mention cheap. Great stuff for hobbyists and even small businesses.

ansible• 2 years ago

This is an interesting and fun project, I was glad to read about it.

It was a bit of a bold move to base this on a Model I. That system had an unreliable expansion interface, limited memory options, and emitted a lot of EM interference.

codewritinfool• 2 years ago

And the ones with built-in CRTs had issues wherein the cathode of the CRT was DANGEROUSLY CLOSE to the main PCB. If you weren't careful cracking that puppy open -- zappo! Fried motherboard, possibly fried you!

I'm curious which model this was. The Model III was the first all-in-one model I had experience with, and the between the motherboard and the CRT neck was a piece of flat aluminum. The biggest danger was potentially snapping the neck off, but there was no danger of touching the mother board. Model 4 was the same configuration. Even the Model II had a metal plate between the CRT and any circuit boards.

jonjack• 2 years ago

respect the buc-ees shirt

anonymousiam• 2 years ago

The author mentions that some programs have made sound with the TRS-80 by using tight timing loops that access the bus(es), which create a lot of RFI that can be received by a nearby AM radio tuned off-station. The software loops can be timed to produce musical notes that will be heard (along with much static) on the radio. Looks like he used the cassette outputs directly for sound in this case.

I noticed that the video link on his web page was not a hyperlink. His video is here: https://www.youtube.com/shorts/JD9sXwgHMfc

I never owned a desktop TRS-80, but I repaired one once after a friend of mine inadvertently put 120VAC on the internal 5V power bus. About 1/3 of the chips were blown.

He told me how he blew it up: The Condor power supply he was using to provide +/- 12VDC needed for the RS-232 EIA voltages to drive his modem had the input (line voltage) present on a the same terminal strip with the +/- 12VDC output terminals. After a few beers, he had dropped some metal object (bottle opener?) and it momentarily bridged the 120VAC and one of the 12VDC outputs. The line voltage found its way through one of the 1488/1489 EIA converters, and onto the 5VDC bus. That was enough to let the "magic smoke" out of about a third of the chips.

https://en.wikipedia.org/wiki/Magic_smoke

I do still have a TRS-80 Model 100 in a closet somewhere.

https://en.wikipedia.org/wiki/TRS-80_Model_100

wang_li• 2 years ago

I may be getting old but it may be that the enjoyment dad is going to get from this is less than if he'd spent this amount of time with dad instead of making a doodad for dad to futz with.

urbandw311er• 2 years ago

We have no evidence that he didn’t.

ForOldHack• 2 years ago

A Whopping 32k on an expansion card! Triple the memory expansion. This is like going from 32Gs to 96Gs, because 64Gbs was just not enough.

"a 48 K machine would have been a very unusually powerful one for 1978." After 1978, it was almost the standard.

tomcam• 2 years ago

This filled me with longing and borrowed nostalgia. I grew up on the West coast but read vast amounts of children’s literature about Long Island childhoods like Josh describes. (I’m a Boomer and eventually realized that such books were ubiquitous because all the big publishers were in Manhattan. The editors just hired their friends, who often lived in the suburbs because they had kids. They could get a few acres for the price of a Brooklyn brownstone. They usually wrote for magazines or ad agencies, a pretty decent living.) These cheerful little books were junk. That’s what I needed. They kept me sane when not taking care of my alcoholic parents or being beaten. It is because of those books that I dreamed of owning a farm, finally acquiring one 50 years after I first dreamed of it, and sadly after most of our children were adults. Despite being in Seattle it has a bit of East Coast vibe.

Josh seems to have a wonderful relationship with reasonably well-adjusted parents. Elsewhere in his blog he describes building not one but two models of his father’s law office, where Josh spent countless hours as a child. What a beautiful thing to be as accomplished as the people in Josh’s family and to be so nostalgic. Gave me shivers!

Bit-banging a BASIC Birthday

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