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@TubeTimeUS
Sep 16, 2021 • 7 tweets • 2 min read • Read on X
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this ISA card is not what it seems! 🧵 Image
oh, but it's just a SCSI card with onboard cache SIMMs and an activity LED, you say. Image
does this look like a SCSI connector to you? it's got 78 pins. Image
these aren't RAM chips on the SIMMs. Image
and these aren't chips you'd find in any SCSI card. these are dual UART chips. yes, this board has eight serial ports. Image
they're not RS232, they're RS485. it uses differential signaling so it can be transmitted over longer distances, and it's multi-drop so multiple devices can share the same wires.
🇨🇦 Image

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More from @TubeTimeUS

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Jun 13, 2023
here's a weird object! it's some kind of foot pedal with an IBM logo. is it for a sewing machine? electronic synthesizer? what do you think? 🧵 Image
it's got a cursed connector! what IS that? Image
amazingly enough, I found something with the mating connector on it! but what is it? Image
Read 24 tweets
Tube Time Profile picture
Jan 11, 2023
hey so remember the world's cutest oscilloscope i picked up last year? i think it's time to fix the probe socket issue.
i printed a new panel insert that has two BNC sockets on it (the original probes would have had captive cables)
the tricky part is that this oscilloscope has a 333K ohm input impedance instead of 1M like umm every other scope on the planet. fortunately someone designed a little conversion circuit...
Read 11 tweets
Tube Time Profile picture
Jan 5, 2023
in honor of Sim Wong Hoo, here's a quick historical review of the Sound Blaster! 🧵
but first we have to go back to their first sound card, the Creative Music System from 1987. (image credit: Bratgoul on Wikipedia)
this card has some special "CMS-301" chips. if you peel back the sticker, they have had their top marks removed. they're actually SAA1099 synthesizer chips made by Philips. Creative wrote music composition software for musicians on the PC.
Read 23 tweets
Tube Time Profile picture
Dec 31, 2022
Tube Time: a 2022 retrospective 🧵
(and stuff you might have missed!) Image
starting things off in january, i found a tube of super old 555 timer chips! i also decapped one of them.
i also started fixing up an old HP 150 computer. it's not PC compatible but it runs MS-DOS--how odd!
Read 65 tweets
Tube Time Profile picture
Dec 29, 2022
today's mini project: fixing this Radius Thunder IV GX daughtercard. it looks fine, but... 🧵 Image
one of the chips has some broken pins! Image
looks like two of the pins got mashed and broke right at the plastic package. Image
Read 11 tweets
Tube Time Profile picture
Dec 8, 2022
on the bench of healing tonight: my coffee grinder which decided to bite the dust. Image
symptoms: i push the start button and the motor just bumps a little bit and stops.
how to take it apart? hmm, i bet there are screws under the rubber feet. Image
Read 23 tweets

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