Repairing the DEC VT100 so I can game on it
We have the follow-up to the DEC VT100 repair series. Let’s fix everything wrong with this terminal so it can go online like it’s 1979!
Part 1: https://youtu.be/Hz0kNKTiM-4
Part 2: This part!
— Links
Technical Manual:
https://bitsavers.org/pdf/dec/terminal/vt100/EK-VT100-TM-003_VT100_Technical_Manual_Jul82.pdf
User manual:
https://bitsavers.org/pdf/dec/terminal/vt100/EK-VT100-UG-001_VT100_User_Guide_Aug78.pdf
Wifi Modem:
Adrian’s Digital Basement Merch Store:
https://my-store-c82bd2-2.creator-spring.com/
Adrian’s Digital Basement ][ (Second Channel)
https://www.youtube.com/channel/UCbtwi4wK1YXd9AyV_4UcE6g
Support the channel on Patreon:
https://www.patreon.com/adriansdigitalbasement
My GitHub repository:
https://github.com/misterblack1?tab=repositories
— Tools
Deoxit D5:
https://amzn.to/2VvOKy1
http://store.caig.com/s.nl/it.A/id.1602/.f
O-Ring Pick Set: (I use these to lift chips off boards)
https://amzn.to/3a9x54J
Elenco Electronics LP-560 Logic Probe:
https://amzn.to/2VrT5lW
Hakko FR301 Desoldering Iron:
https://amzn.to/2ye6xC0
Rigol DS1054Z Four Channel Oscilloscope:
https://www.rigolna.com/products/digital-oscilloscopes/1000z/
Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:
https://amzn.to/3adRbuy
TL866II Plus Chip Tester and EPROM Programmer: (The MiniPro)
https://amzn.to/2wG4tlP
https://www.aliexpress.com/item/33000308958.html
TS100 Soldering Iron:
https://amzn.to/2K36dJ5
https://www.ebay.com/itm/TS100-65W-MINI-Digital-OLED-Programmable-Soldering-Iron-Anti-static-Structure/113382669853
EEVBlog 121GW Multimeter:
121GW Multimeter
DSLogic Basic Logic Analyzer:
https://amzn.to/2RDSDQw
https://www.ebay.com/itm/USB-Logic-DSLogic-Basic-Analyzer-16Ch-100MHz-4Ch-400MHz-Xilinx-Spartan-6-FPGA/202543965672
Magnetic Screw Holder:
https://amzn.to/3b8LOhG
https://www.harborfreight.com/4-inch-magnetic-parts-tray-90566.html
Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
https://www.ebay.com/itm/14-16-18-20-24-28-32-40-pin-IC-Test-Universal-ZIF-Socket-Fs/303206721971
RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)
http://www.retrotink.com/
Plato (Clone) Side Cutters: (Order Five)
https://www.ebay.com/itm/1-2-5-10PCS-Micro-Scissor-125mm-PLATO-170-Electronics-Cutter-Side-Cutting-Pliers/163458746184
Heat Sinks:
https://www.aliexpress.com/item/32537183709.html
Little squeezy bottles: (available elsewhere too)
https://amzn.to/3b8LOOI
— Instructional videos
My video on chip removal without damage:
— Music
Intro music and other tracks by:
Nathan Divino
@itsnathandivino
source
Nice games! Maybe you should skip the esp32 thing and just go in through a serial port on a linux box with a null modem cable. Something like a Wyse Cx0 (which are only about $15) with linux on it will let you login through the serial port, and there you can telnet anywhere you want.
Adrian, on your buffering issue, I think this is the cause. The speed you have set on the terminal is between you and your faux modem. What you need to do is within the environment once you log in. If you type "stty -a" you can see what the system is expecting you have based on the telnet interface. I think the command you need is either "stty baud 19200" or replace baud with 'speed'. That will tell the remote terminal how fast to send you data. I used to find 4800 or 9600 was a nice fast scroll reading speed.
If you were directly connecting a termial in DCE mode you are assigned a TTY inerface on the server, that would query the the terminal for those settings.
When you Connect as a session via ssh or telnet the unix host asigns a VTTY (Virtual TTY) to manage the communication.
Theres a sticky substance around the BELL key…
Takes me back…
My first professional computing was done on a VT 220 connected to one of the first VAX 8650 clusters. We had a couple of VT 100s in odd corners.
FORTRAN 77 FTW and <waves> to any other UK Cold War Scientists out there.
Can't get over how sharp the text was on the display and the smooth scrolling.
5150 is the poloce radio call sign for a pscyzo
The sound of a modem connecting is the most beautiful melody of my youth. 🙂
Somewhere in the mid-90s, when some civilization came to Poland, my parents bought me a 14400 us robotics modem for my computer. I remember that discovery of the digital world and terribly high phone bills 🙂 because in Poland you paid for the connection time.
@19:58 that is so cool.
how good is that Zoyi Zt-703s? I'm so tempted to buy one off amazon.
Another awesome rescue!
The burn dot in the center of the screen is defenitly from the "turn-off" sequence. There should be a circuit with some cap to push the drive voltage to black level during power off to avoid that. This cap is probably broken.
45:57 is there a StarWars vt file? Like when we telnet towel blinkenlights nl
18:41 Man, that thing goes all the way up to 19200 baud??!!! I was expecting it to max out at 9600 like my other terminals from the late 70s and early 80s…maybe this one is newer than I realize?
8:17 I am also SO glad that you walk us through taking the time and effort to determine precisely WHICH caps are bad, vs just "recapping" and replacing them all… Thank you!
I SOOOOOOOO love that you did this! What a classic terminal, now in great hands!!!
The VT100 is design classic. I loved using them early in my career.
Regarding the issues with software flow control once you connect to the server from your modem emulator, it might be that that the modem is deferring flow control to the connected tty. On Linux you should be able to check if xon/xoff is enabled on your tty by running 'stty -a'. '-ixon' in the response would indicate it is disabled. If disabled, 'stty ixon' would enable it.
They + connections are obviously not joined or C406 would be shorted, along with C104, R335, C440, etc.
3:08 The 555 found his way into the CRT board.
I have seen old or abused SOD-57 and SOD-64 package diodes fail that way before. Nothing you did caused it. I suspect it was only a problem with some manufacturers because the ones I buy from Vishay never have that problem.
F**king superb! So many memories brought back from watching this. Thanks Adrian 🙂
Super dork.
You need a check list. first thing visual inspection, second clean and reseat all the connectors, retest, third replace all the capacitors they cost next to nothing and they are very old. forth test the transistors. and so on.
If it's tar on the keys? Try margarine, then a soap wash. IPA just moves muck around.
ComplexSimpolUSgbEN2ovwotEUsayPCdigitALcapFeynmanismIndivIDhayesMowTailDosCp/mDescryptArDawYellowDogLampwwoolambdaz!
Wish they had included the flexing toes at the end of Bambi vs Godzilla.
Note! You don’t turn back down the voltage. You can still see the raster. Assume you will fix but ya know
So kool to see this thanks so much Adrian
Visual Technology made a direct competitor to these called V-100. They went as far as to include the Setup key and functions, however, instead of setting virtual switches, the options were laid out in small fields that were toggled with the arrow keys similar to Setup B on the DEC VT100.
Like the VT100, the V-100 used the same NVRAM chip. Overall, these are quite reliable but occasionally we'd come across a few that were bad. While primitive by today's standards, it's this technology that eventually became thumb drives and SSDs and other flash media.
When I left Visual in 1987, I ended up eventually moving into MIS at a company that ran multiple VAXs and had some VT100s and other terminals. Having come from a terminal repair background, I was given the task of going through a pile of dead VT100s and repairing them during my 2nd shift operator job. I was lucky that the company had some schematics available and I had fun troubleshooting the motherboards, power supplies, and CRT boards. This is a job I miss today even in my retirement.
Are you sure it's the wifi/modem, not the telnet setup on the server side? You might try connecting via telnet to somewhere else as a test. And/or, try a much slower baud rate, like 1200 or even 300 to see if the ^S, etc. now work.
Docker? Ick!
Very cool as usual!
Ugh, Adrian, you're infecting me, my eyes couldn't move from that awful tar glob on the H keycap, I was going "ewwww, ewww, dude, clean the H, I'm gonna be sick"…. I'm just having fun with ya, but i really did think that. What an excellent restore, I just LOOVE seeing a classic VT100 doing it's thing, those ASCII demos are just spectacular! Much love to your and your channel my dude.
Oh the memories, I remember getting a PDP 11 and decks scope from the local high school when I was a teenager, my only goal was to figure out how to get my 8-in floppy of lunar lander working! What little did I know that fatal sector flaws would keep me from achieving my goal…
does the terminal support hardware flow control RTS/CTS (this requires the correct wiring on the serial cable to work. I think pins 7 & 8 are connected to the modem) also set the modem to hardware fowcontol at&k4 also in agetty -h or –flow-control turns on xon/xoff flow control too
VT100 has a graphics mode as well you should try out. Most VT100 emulators do not emulate it, but some actually do have support for graphics (usually labelled like "VT100 Graphics Screen" on a separate window). And the buffering problem is your host – Linux doesn't really support baud rates for pseudo-terminals. You're actually better off hooking the terminal to the serial port of a Linux machine (yes, it still supports serial terminals) and trying stuff that way. PTYs are just sent as fast as the network allows.,