In the 90s I rescued a DEC VT100 that I used to write code and manage VAXen and aside from occasional
stints as a serial terminal for some of my bigger DEC machines it's largely sat on a shelf in my garage gathering dust and
spider corpses. A couple of years ago I discovered a project by a fine German bloke called Joerg Hoppe who had
built a thing called a DECbox using nothing but a VT100 and a Beaglebone Black single board computer.
Said Beaglebone was running a multi-machine emulator called simh originally coded by ex Digit Bob Supnik
but now maintained by a lot of others too.
I just happened to have a Beaglebone thanks to a mate over in Ireland who made electronics for fruit machines, so
after much studying of parts datasheets I decided to build something similar for myself. Only problem was my VT100 had died in all its years
in storage so job number 1 was 'fix VT100'. After a lot of careful analysing and probing in the PSU (I'm not a fan of working on these live)
with many emails to/from expert extraordinaire Tony Duell I discovered one of the power resistors had failed, thankfully it
had failed open circuit rather than shorting which would've been much messier.
With the VT up and running again the next thing to address was the lack of TTL-level serial interfaces on the Beaglebone.
Joerg had used a cape made by Philipp Hachtmann but several emails to buy one of his spares fell on deaf ears so I set about building my
own using both halves of a MAX232 serial converter. One half could act as the BBB's console and the other could be the actual terminal.
It took a couple of prototypes until I found a good enough layout for what I needed and with a swift bit of metalwork later it was all bolted
to the cardcage frame of the VT.
Power next, and while the VT's PSU was more than capable of powering a BBB while the terminal was powered up I needed to also
run it independently off its own 5V supply. I built a switchable power box that sat between the main PSU and a separate 5V input for a regulated
2A brick which sits in the bottom of the terminal. For the main PSU I added a feed from the main power input of the VT's motherboard.
The BBB itself runs Debian Jessie with simh compiled locally which took quite a while :) Disk images to run under VAX or PDP emulation are mostly
images of my own VAXen from both work and home created using an Ubuntu PC containing a SCSI adapter. There are also some PDP images for OS/8 and Unix with
hopefully one of my own PDPs from the 80s when I get time to attempt the imaging. Latterly I added Multics to the collection because why not.