foone Profile picture
12 Jan, 30 tweets, 7 min read
So the last part of the Datachecker that I haven't even done a basic overview of is this huge thing, which I've been calling "the analog box". Spoiler alert: that name is inaccurate
This was mounted right behind the front panel, between the two hard drives.
It turns out each one has a separate on/off switch.
So, opening it up required a 3/16" socket wrench, and it turns out it's 3 boards! or... five. because some of them are doubles.
And at the bottom, they're labeled Disk #1, Floppy, and Disk #2.
So, yep... they're power supplies.

at this point I think like 90% of this fucking computer is power supplies by volume
Specifically it's a "Disk A Power Supply +5, +24v PWA 9809344"
And the other side is a "Disk B Power Supply, -5v, ±12v, PWA 9808665."
And here's the floppy power supply. It's identical to the hard drive ones, just without the secondary board to add -5v and ±12v
These little power connectors are interesting. They look like this when connected.
To remove, you just pinch them...
and it slides right out.
They're polarized, too.
I'm not sure what this is, but it looks like some kind of tasty-jello
BIG CAPACITOR
The final thing was this device on top of the box:
It's a T-O-D 60TG12, which is a "THERMOSTATIC LIMIT SWITCH".
I'm not sure which this was hooked up to. It's either a device to turn on a fan when it gets too hot, or to cut all the power if it overheats.
and for reference, this is what I'm talking about: my National Semiconductor Datachecker 1730 minicomputer.

So...
There's a power supply stage zero, which takes in one 3-phase-AC connector and converts it to the fan voltage (12v, I think?)
There's two of the stage-1 power supplies, which take AC and produce 61.1v:
there's two of the stage-2 power supplies, which take 42-68 volts and produce 5.1v and ±12v:
Then there's the power supply backplane:
which has THREE +5v boards, two battery chargers, then two more boards: supervisor BD and aux board.

so lets call that... 5 more power supplies?
then finally we get to this one I'm looking at today, which is three power supplies:
two that are +5v, ±12v, and 24v, and one that's just +5v and +24v.
so by my calculations that's THIRTEEN FUCKING POWER SUPPLIES
This thing was designed to run grocery store cash registers, and they want to minimize possible downtime.
so it's functionally two computers in one case with fully separate power supplies, and they both have separate battery backups in case of power failure
the battery backup is part of why it's so complicated:
Instead of just going AC->12/5, they go AC->61->12/5.
This is because the 61->12/5 power supply can also run off the 48v of the batteries.
The batteries are also huge, of course.
They provide 48v and 5 amp-hours.
so my plan for when I eventually try to power this thing on is to completely skip using any of these power supplies.
They're from the mid-80s and haven't been powered on since the mid-90s: there's just so much that can go wrong (though mainly capacitors)
so I'll build my own power supply using modern parts and provide the required voltages to the assorted parts that need it: the computing backplane, the front panel, and the disk drives.
that's way in the future, though. I need to do a lot more documenting and dumping before I even consider that, because there's every chance that even with replacing the power supplies, I turn it on and it immediately fries itself.

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More from @Foone

14 Jan
Something that I didn't realize but hurt my brain to learn:
John Norman (aka John Frederick Lange Jr.), of the Gor series of sci-fi/BDSM novels, is still alive.
He released two books (one of them a Gor book, #35), in 2019. Image
I guess with the fact that the series started in 1966 and feels like it's always a historical thing... I assumed he had to have quit writing and/or died back in like 1986.

Nope. Still alive, he's 89, and was apparently still writing as of 2 years ago.
also, my brain being what it is, I totally just googled for the book's cover image by entering "trans man of gor" which is NOT the title.
Read 14 tweets
14 Jan
gonna get in line for the vaccine because I've heard all these urban legends about tracking microchips

and I think I might be able to root it and install Doom
supposedly bill gates is involved, right?
so it's probably like a miniaturized 386 running ROM-DOS.
the doctor walks in, looks down at my charts, and sighs.
"well, the bad news is that you've got the virus. I'm sorry..."
"and the good news?"
"well..."
*at doom's gate starts faintly playing from my lungs*
Read 44 tweets
14 Jan
My favorite part of being sick with ADHD (by which I mean having ADHD and being sick for unrelated reasons, I'm not ill with ADHD, at least not any more than usual) is when you're too tired to do more than one thing at once, but this doesn't affect your need for stimulation
so you're doing one thing while trying and failing to find something you can do as the second thing. I've refreshed reddit, twitter, tumblr, and ebay about 20 times each, tried to work on about 4 hardware and 2 software projects, and it's just not working
so I'm just laying back in my chair watching some letsplayer shoot zombies on youtube and VIBRATING WITH ADHD BOREDOM
Read 22 tweets
13 Jan
fun fact: for a brief period in the early 2000s, Microsoft tried to increase the number of users who would register their software by employing hypnosis Image
This is actually the registration card that came with this odd piece of microsoft hardware. It's a set-top box from 2001 which displays JPEGs on your TV, off floppy disks. Image
I guess the idea is that it let you use a big living room TV to look at photos, instead of a small PC CRT? Image
Read 61 tweets
13 Jan
shout out to ebay who periodically decides my search on "minisport" isn't getting enough results, so it decides I must have spelled it wrong, and corrects it to "mini sport", then suggests "men sport", and I get emails like this: Image
I DO NOT WANT TINY BASKETBALLS, EBAY
I WANT ZENITH MINISPORTS Image
anyway I went in and fixed the search to have quotes in it.
ebay will fiddle with your searches unless you quote it, but sometimes it may take months before that has a noticeable effect
Read 5 tweets
13 Jan
Here's a CPT Phoenix Jr Terminal on ebay.
And wow, it's... weird!
Check out that portrait CRT, and angled keyboard! Image
It seems they tried to make the keyboard symmetric for... reasons, but the left numpad isn't a numpad, it's just got a bunch of custom keys, like TASK and PARA and LINE/SKIP/OUT/ADJ.
I imagine that was designed for customizing for the specific terminal task in mind? Image
Real Monitors Have Curves Image
Read 28 tweets

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