looking through some old photos, i found some neat pictures of IC chips. this one is a 7805 regulator. Image
8755 16K EPROM + GPIO Image
Intel 8080 CPU.

(this one is from National, i think they were a mask licensee) Image
Mostek 4116 - 16kbit DRAM Image
LM113 voltage reference. you can count the transistors! Image
Intel 4201 clock generator (for the 4040 CPU) Image
here's the Intel 1702, the first commercial EPROM chip. Image
intel 4289 standard memory interface. (for the 4040 CPU.) note the bizarre damaged bond wire and repair (with solder!) Image
AM2909 bit-slice address sequencer from AMD. Image
SP3725QD quad NPN transistor array. each transistor is a separate die! Image
AM2812 32x8 FIFO RAM (with bonus serial in and out!) Image
National Semiconductor 7438 quad 2-input NAND gate. buffered, open collector output. the lower left corner is missing due to my primitive decapping technique 🔨 Image

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More from @TubeTimeUS

5 Oct
this is one of the world's first electronic calculators, the Friden EC-130, which came out in 1964! it's a really fascinating machine, so let's look at it in more detail. 🧵
you could buy it for about $2100 back then (about $20K now!) isn't it pretty though?
let's take a closer look at the screen. these are not LEDs or vacuum fluorescent displays, this is actually a CRT!
Read 51 tweets
1 Oct
this neon lamp should never light up! there's a fascinating reason why... 🧵 Image
ok so what is the circuit? this is a 3Com Etherlink card from the late 1980s. you can see the neon lamp in the lower right. actually there's a bunch of other interesting things going on but first, the neon lamp! Image
the circuit on the right side of the Ethernet card interfaces to the external AUI transceiver (the 15-pin D-sub) or a coaxial 10Base-2 network. the whole circuit is isolated by those two transformers, and i've put a red line so you can see no traces cross over. ImageImage
Read 14 tweets
25 Sep
this video landed in my youtube feed this morning. give it a watch, but try not to get too angry; there are some good lessons to learn. 🧵

this is the IBM 7496 Executive Workstation. i've never heard about it before, and it's probably quite rare. but rare doesn't necessarily mean valuable. Image
looking at the machine, it has some odd features. the tilted power jack is unusual; they must have run out of room in the case. Image
Read 55 tweets
24 Sep
this desk fan is 85 years old and still running strong. how would YOU design an electronics gadget to last 100 years? what components would you use? what potential failures would you expect?

bonus: how would you make it last 200 years? how about 500 years? Image
thanks for all the responses. i noticed some interesting patterns:
✅assume humans are around the whole time, so make it easy to repair. *lots* of subtlety to unpack on this one.
✅material choice is critical
✅keep it as simple as possible, but as complex as is needed.
honestly i didn't think of the repair thing even though it may seem obvious. i guess i was thinking about a device that could survive 200 years in a dusty closet. but repair is very important!
Read 32 tweets
21 Sep
this afternoon i built a really clever radio transmitter using a circuit i found in a book. it's really quite ingenious, so let's dig into it a little bit...
first, the book. it is "Communications Projects" in the Engineer's Mini-Notebook series by @fmims! i bought this maybe 25 years ago from Radio Shack.
here are the plans. i'll dig into the details of the circuit in a bit, but let's go through the construction a bit.
Read 46 tweets
18 Sep
welcome, new followers! you're probably here because of my PG&E thread, but there's a lot more stuff going on here. (🧵)
first up is the MOnSter 6502, the world's largest 6502 microprocessor. (you may have seen my pinned tweet about it). the 6502 is a microprocessor that was the heart of the original NES, the Apple II, the Commodore 64, the BBC micro, and more.

the MOnSter 6502 has a website, monster6502.com. we were going to crowdfund and build more, but then COVID threw a big wrench into those plans. someday though. Image
Read 36 tweets

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