Bringing An ADM-3A Back To Life

[David] at Usagi Electric ended up with an old Lear Siegler ADM-3A terminal in a trade a couple of years ago. But the CRT face was plagued with so-called cataracts, and the condition of the insides was unknown. The video ( below the break ) shows the restoration process, which went quite smoothly. [David] was relieved that the CRT repair in particular was easy, a fact he attributes to the Texas weather —

ADM-3A Under the Hood

The temperature was 110 F / 43 C when he set the CRT outside to bake in the sun for a few hours. Afterwards, removing the “integral implosion protection” plastic screen went better than expected. Everything cleaned up nicely and the screen reinstalled. Introduced in 1976, the main electronics board is chock full of TTL chips with nary a microprocessor in sight. Fortunately the board was substantially intact, and a single missing chip was found hidden underneath the board. [David] gets the terminal up and running in short order, and is confronted with an annoyance familiar to gray-haired programmers who grew up in this era. Most terminals had different sets of commands to control features such as cursor control and clearing parts or all of the screen. Programs often assumed a certain type of terminal. Some terminals could be configured to behave in different ways, and some programs offered the user a choice of terminals. Today your terminal emulator probably still has a few choices of which kind of terminal to emulate, VT-100 being the most common. And eventually some operating systems provided a terminal abstraction, like Unix’s termcap for example.

If you were around in the era where terminals like the ADM-3A were scattered everywhere, what was your favorite terminal and/or terminal feature? And today, do you have any favorite terminal emulator to recommend? Let us know in the comments below.

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