PDP-9 Restoration Blog Starting 2020

Go to the earlier restoration blog.


We tried the ASR-33 Teletype from the Altair 8800 as the system console

We blew one of the 3A fuses because the wires for the paper tape reader control inside the TTY were reversed

This looked like a short to the PDP-9, and the fuse protected everything

After we fixed the paper tape reader control wiring the TTP keyboard and printer worked OK

The paper tape reader would not turn on

We checked the transistors and diodes on the W040 that drives the printer and controls the reader

Diodes D2 and D7 were shorted

We replace them with NOS D-662 1N645 parts

The paper tape reader in the TTY is enabled when ADSS first boots, but is disabled after the first character is entered

Looks like we have some debugging to do in TTY input circ