Welcome to Usagi Electric!
On this channel, we dive into old school technology, focusing heavily on vacuum tubes. My primary goal is to build computing circuits based off the legendary machines of yesteryear, only with a slight modern twist. All the tubes will be operating with very low voltages on the plate, making the projects safe and easy to follow along with. So, lets grab our multimeters, some random tubes and a low voltage power supply and have fun!
Usagi Electric covers one of my main passions, while my other main passion can be found over on Usagi Motors.
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That's IMPRESSIVE!
quite/quiet huh? I thought people only made that problem with typing
Interesting. He has a Cent-you-rion. Not a cent-oo-reon. Ahhh the venerable CDC drive. The office girls loved this machine doing a seek test on the disks, they would come out in ones and twos to stare at the heads linear drive, go back to the office and giggle. Cant understand why? Biggest problem with these was head changes after a disk was changed into an image of the rings of Saturn. Its such a long time ago and there have been many many disk drives, maybe i have the wrong one but I think that when adjusting the heads it is possible to pickup the wrong track as the head adjustment will cover several tracks. What you can get is one platter adjusted correctly and the other platter one or more tracks out, so using a data disk output as an alignment is not actually satisfactory, the alignment should be done with a diagnostic disk. As I said, so long ago and so many drives ago, maybe I have this drive and another confused.
The palpable excitement Dave expresses when he gets things working in this video is really heartwarming. :D
Get an Apple I
Hello Usagi. Doesn't your fix seem a little over-engineered ? Wouldn't it have been simpler to bend out pins 17 & 40 on the UART, bridge them, and run a 'bodge' wire to a 76.8KHz signal ?
Careful with that Seagate drive. Had one of those back in the day, and yes it's about 38M. The clicking you hear at first is the heads unlocking, and the sounds it's making otherwise are actually about what you should hear from it during startup. These drives in particular had a problem with heat. Make sure you have the drive board DOWN in all cases. If you put it board up, it gets hot enough to unsolder itself!
Heh. When I saw the title of this video what came to mind was some full height drive of maybe 5 or 10MB capacity and with an ST506 interface. I actually have run across drives like this, one where a guy actually had one with legs on it and brought it in to me wanting to know if there was any way that I could interface it to his c64. :-) Then there was a GRI mini in several racks that had a couple of these type of drives in it, I think in that case the capacity was 10MB + 10MB rather than 5MB for each platter such as you describe here. The power supplies were different, being completely enclosed and connecting to the drive with a thick cable terminating in an oddball multi-pin connector. I used to have a platter hanging on my wall that had a head crash on it, not sure whatever happened to that. It's been a really long time since I had to troubleshoot anything like that! Worst I can remember doing is the external HD box that hooks up to my Osborne Executive computer, it had a linear power supply in it and a brief power glitch wiped out the first track on the drive. After putting a switching power supply in the box I laboriously re-built that track using a sector editor, and recovered all of my files. That drive had a whopping 20MB of capacity. There's also a Kaypro 4 around here with a different external drive box that has a pair of 40M drives in it, plenty of capacity for when you're running CP/M.
Flawless work !
Dude, you've gotta get a Hakko desoldering gun. They're a game changer.
That hard drive seek test sounded normal. Perphaps there's no DOS on it or there's something wrong with the controller card?
Do you ever visit VCF midwest?
Nice mod but you didn't need to make your daughterboard. After socketing the clock rate multiplexer chip you should be able to use a jumper wire between the 78kHz input pin and the output pin.
I'm an Electrical Engineer that worked on old computer systems including removable drives like you show here. We had alignment disks that we would load in the drive and align the heads using an oscilloscope. After alignment, regular disk packs could then be used.
With this opamp you could build an analog computer
The i80x386 was my first IBM PC compatible :D
That bodge board is perfect! So cool that you got to do a period-correct modification to the machine. Great work.
incredible use off molex conector at until on last days😂
I'm in awe of your electronics skills - I wish i had them!
Fascinating video. Also, just curious what app you’re using on the phone there for the audio pickup. Ta
That was fun (at least to watch ;), thanks for sharing it.
Why? !
I miss Radio Shack. The last thing I bough from them was a cordless home phone for my ex's grandfather in Fort Myers Florida. That was probably 2011. I went to the back of the store where all the components used to be in the big long gray drawers and it was all cleaned out, no real parts to speak of. A few bags of resistors hanging on a card, but man.. when I was a kid in the 80s Radio Shack was 15 minutes from my house growing up and I spent a LOT of time there!!
could you build a buffer box that could receive one buad on one side and send at a different buad on the other side?
Wow! Very interesting!
Working on anything with a device called a ‘velocity transducer’ is maddd nerd currency bro. Hat’s off. Jealous.
Nicely done. Sometimes old computer repair just goes like that. Have fun at VCFSW!
Great video and a cool hack
Quick tip with the desoldering iron is that you can suck the solder out and break the pin free at the same time. I have that same RadioShack desoldering iron and as the solder melts I apply gentle pressure to the pin to center it before I release the bulb. This gives enough room to break the meniscus once the solder is gone, and the IC usually lifts right out by hand.
I LOVE those RadioShack solder suckers! Have two of them and they are absolute wonders for desoldering pretty much anything.
Love your videos, but the 14+khz sound of the monitors give me headaches
I know absolutely next to nothing about early computers and finding your channel randomly recommended to me has made my month! Keep working on these! It's very interesting to see as a mere 26 year old.
I'm 41 and still these were before my time as well, however I see some resemblance to early IBM MS-DOS PCs.
Are both terminals running the same CPU clock speed and processor versions? It appears there were three versions in 3, 5 and 6 MHz.
*_HEADS_* : loaded *_MY HEAD_* : unloaded
so it's not y2k compatible?????
9:11 That plate is why you have those giant fans you mentioned in the last video. While they don't get super hot when being cooled, they generate a lot of BTUs. While a DECVAX is not the same, it required a lot of cooling and its own power conditioner (which also needed cooling). The server room we had ours in back in the 90s had a raised floor for all the cables, a giant power conditioner and it's own several ton AC. There were other things in the room, mostly just X86 boxes running Netware (they were running a special NLM and there was like 12 of them configured as computation servers). But they didn't need it, the DECVAX did (I'm calling it that to avoid autodelete from the last 3 letters). One day the AC crashed. That room, normally like 55 degrees was 90 plus degrees in a couple of hours even with all the PC servers down. The room was at least 12x12x8, probably much larger.
I am by no means an expert on old computers. That being said, I turn wrenches every day. That air filter media looks a LOT like what newer Ford Super Duty pickups, and a lot of OE Donaldson air filter assemblies. Maybe, just maybe, you could 3D print a housing that can have the filter media replaced? Then, you can source generic air filter media and have a brand new air filter that is completely serviceable.
not the first hard drive 1956 - IBM 350A, shipment of prototype disk drive to Zellerbach, SF CA, USA?
These relays are so like, soft sounding. They aren't as aggressive as others lol
Stupid story about the PCB boards for the ADDS Regent series. All board chips had a name legend identifying the chip used. The son-alert which sounded local bell (aka teletype like) had an ID legend it said "Beep Beep" but it could not be read because the sounder cover obscured it. Someone in sales got peeved when a customer inquired about it. Engineering services got a little reaming out for it. Sales people are just too stiff, loosen up dude and dudets.
Question at this point: If you use 9600 baud but write a program that throttles the output to 300 chars per second, does it still flicker?
When I heard the pc first boot up, the beep, and the floppy drive seeking it literally brought me to tears. I was a SYSOP of The Lair BBS in 1988 and it has been forever since I had last heard the bootup noises. Thank You.
My father used some hard drive platters like these as aerial analog tv antennas at the time...
Hi David, I watch all your videos avidly, and in spite of the fact that I am an electronic product design engineer with over 40 years experience, I am in awe of what you accomplish. I particularly like this hardware fix you devised to alter the baud rate from 9600 to 4800, however you went about this in a very roundabout way, given you did not want to alter the mux board you could have accomplished this with one wire link and lifting a pin on the U_K1. Since I can't see the whole schematic I have to make an assumption as to which pin has the 9600 baud signal, all you really had to do is remove the 9600 baud from U_K1 and substitute the 4800 baud signal. If the 9600 baud signal is on pin 12 of U_K1 all that you needed to do was cut pin 12 near the PCB, bend the IC leg up so it is free of the board and link from pin 13 to pin 12, this means when the selector U_1K is in the 9600 baud position the signal is actually 4800 baud, to reverse the mod, remove the link between the U_K1 pins and link from the lifted pin back to the PCB pad that it was originally connected. No risky de-soldering and only only a pin lift. Keep the videos going, I enjoy them so much.
Loved that you used a vintage Casio Mini 8 to calculate the baud rate! To be consistent, I am sure you will use a slider rule to make any calculations for the Bendix machine 😂
Awesome solution! Shocked by format command😱
2:20: Buttler Tech's "hands-on" program seems pretty plugged-in, I see.
Well you managed to find someone who could program the Centurion without the full instruction set... There must be someone on your Discord who's just saying "Dissemble an Adds Regent 200's firmware... easy as pie!".... Well, y'know, fingers crossed an' all. Oooh... having just read your pinned comment... yeah, if it's 8085 code, I'm almost tempted to give it a try. ;)
Little bit harder than you think. Besides the three 2716's roms on the right there was another 8755 eprom (2k with 2 bidirectional 8 bit ports) original chip tasked with keyboard interfacing (by 8085 control) located next to 8085 on the lower left side. Except for the three 2716's none of the eproms were contiguous address mapped. The regent series was the first micro-controlled terminals. Before that terminals were built out of TTL chips, among a few other chips required to push static shift memory chips (terminal display buffer). Back then National and Texas instruments loved us. Buying over 250K pieces quarterly. Even Amphenol/3M sold us ton's of connectors.