Atari 1040 STf upgrade and repair

(Originally a Twitter thread started June 12, 2022)

June 12, 2022

Today I’m revisiting my #Atari 1040 STf that I got last year from @benjedwards. I’d like to fix the floppy drive (doesn’t seem to read or format disks), upgrade TOS, and fix the two broken keys on the keyboard.

With some very kind help of @Recta_Pete, I got the parts to replace the broken keys. He also lent me an external hard drive (!) and Atari SC1224 monitor (!!)

RF shield and power supply removed reveals the motherboard. Looks like I have the 6 chip TOS board. Also, great to see the giant DIP64 68000 here.

So, do I round up six 27C256 32KB EPROMs, figure out how to split them Hi/Lo, and burn them myself or just buy them ready made?

.. some time passes ..

Somehow, I pulled together an assortment of 256Kb UV EPROMs, erased the non-blank ones, and programmed a set. They’re a mixture of speeds which likely isn’t good. But let’s see if this works.

Installed the 6 new EPROMs and wow, it seems to work! As I understand it, it’s Rainbow TOS because the Atari logo cycles through colors in 1.04.

July 4, 2022

Time to repair these two broken keys on the Atari 1040ST. Thanks to @Recta_Pete for the parts!

There’s so many screws on the back of the keyboard I lost count. Keyboard is dated March 26, 1986.

Circuit board separated from the top reveals a ton of rubber domes that thankfully stayed in place, except a few. They provide the spring action and a conductive underside for contact closure.

The old broken posts simply slide out and new ones inserted. New key cap snaps onto the posts. Reassembled and it works great!

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