AT&T 4425 (Teletype 56D) repair

Seth Morabito lists at
Tue Apr 5 12:05:29 CDT 2016

About a month ago I was given a very nice AT&T 4425 terminal, which
was AT&T's OEM of the Teletype 56D.  Alas, the terminal suddenly died
on me last week and I'm going to have to dive in and figure out why.
It appears to be something going wrong with the digital board, not the
analog, since sometimes I can get strange characters to show up on the
screen (but not always).

I did my normal searches of BitSavers and Google, but I haven't found
any schematics for the 4425. I don't suppose anybody has them?

At least it looks easy to work on. Kudos to whoever designed the
innards, it comes apart very easily and cleanly.

Seth Morabito
seth at

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