Notices by Tube❄️Time (tubetime@mastodon.social), page 3

pod1 and pod2 are on the connector nearest the edge of the board (middle connector is for 3 and 4). pod1 chips are on the bottom of the board, pod2 chips on the top. and bit 2 is on this wire coming off the connector. but i suspect a problem with the resistor array tied to the outputs of the comparator chip.

whoops, spoke to soon. it fails 1 of the comparator tests. now i just have to figure out which one it is physically on the board...

pulled the chip off the other card. uh that entire via was corroded away, even part of the trace on the other side. no wonder I couldn't find any copper.

that worked! the card passes all the self tests now.

quick diagram of the resistor array, a 4816P-B07-000. the comparator output goes to pins 1, 3, 5, and 7. pins 2, 4, 6, and 8 are grounded (so the 670 ohm resistors go to ground). the outputs to the FPGA seem to be on pins 10, 12, 14, and 16. the remaining pins go...elsewhere. i suspect it's some sort of termination network that might do some level shifting. perhaps the comparators have ECL outputs or something.

the acquisition ASICs are not 100% figured out yet.

good progress the last few days. i've mostly figured out the pinouts of the HP custom comparator chips and timing zoom chips.

figuring out the mapping between the comparator inputs and outputs. these chips are not off the shelf!

oh no

still ohming out the VRAM to ASIC nets. I made these little paper guides to help me figure out which pin is which.

here's a draft schematic of the HP 16717 logic analyzer plugin!

https://github.com/schlae/hp16717

and, wrapping up 2025, this December i've been reverse engineering the HP 16717 logic analyzer card. they tend to get corroded and they're hard to repair, so this should help folks out.

https://mastodon.social/@tubetime/115741254454906195

in November i reverse engineered a bunch of disposable vapes and put the designs online. they're quite hackable!

https://mastodon.social/@tubetime/115555385897273188

October was busy IRL so i really only had time for a fun meme.

https://mastodon.social/@tubetime/115460910142265494

that about wraps up the highlights. there's a lot more if you go through my Mastodon (and Bsky) backlog.

on to 2026! wishing you all a happy new year 🎆

finally, in August, i was able to reverse engineer the Raspberry Pi Compute Module 5! wow!

https://mastodon.social/@tubetime/115085637853254173

turns out folks were retrocomputing even in 1976.

https://mastodon.social/@tubetime/115042807696749887

Check out this chip with a tiny window!

https://mastodon.social/@tubetime/115041751407817367

Also in August, a new book came out--I somehow found the time to be the technical editor for it. it's great, you should go read it.

https://mastodon.social/@tubetime/114989988735356677

June: i got an early video frame grabber card for the IBM PC and reverse engineered it.

https://mastodon.social/@tubetime/114701449170193069