Mechanical Nightmare

Thousands of moving parts in this old Olivetti machine!

One of my latest projects is to bring this old monster back to life. It is a 99.99 % mechanical computer terminal with almost no electrical parts. You can type and send ASCII chars, receive and print on paper, punch and read paper-tape, all with a blazing speed of 110 baud! It would even accept two keys pressed at the same time, and it was rather silent due to the muffled enclosure.

I once met a former Olivetti repair-man, and he claimed that it had around 10,000 parts (which I doubt, but I can calculate at least 2,500, which is still a lot!). He also said that many parts would have to oscillate at their operating speed, also during idling, to overcome delays. For the same reason the excess amount of small metal parts, springs, washers and adjustments should be in perfect shape for the machine not to jam. The only “electronic” part in the data path is a high impedance bistable kind of solenoid receiving the incoming data. The motor speed is regulated by a centrifugal switch.

I have kept copies of two manuals, and this is the RxTx circuit:

…and this is the motor circuit:


We used it back in the late 70’s when we assembled microprocessor code. The assembling process would take several hours, so we would start it before we went home for the night. After assembling we made a punch-tape and sent i to a company that would make ROMs for us.

The terminal was originally a leftover from a bank, and already outdated when we used it. I have kept it for many years, stowed away in garages, cellars, barns, etc. Once in a while I would take it out and start it, but the last time I tried this, it gave a loud “poof”, and the lights went out. I turned out to be one of the noise-reduction capacitors that had died. It should be easy to fix, as long as faults are electrical and not mechanical. If faults are mechanical you can probably get an idea from the following pictures, of how complicated it is to repair. I will probably post some videos when I have it all up and running.

The exploded capacitor:

Keyboard and control keys:

Carriage with type-wheels:

Control keys mechanism (part of it):

“HELLO ID” code wheel and Tx contacts:

Rx bistable relay:

Rx decoder (part of it):

Rx to papertape-puncher couplings:

Main motor couplings and gears:

Keys connection rods and Tx coder:

Speed regulation (part of it):

Paper tape puncher:

Paper tape reader:

Main drive belt and paper advance:

Secondary drive belt and paper tape puncher drive:

Part of carriage advance mechanism: