ASR 33 Teletype

In the earliest days of personal computing there were few reasonable options for user interface. Video terminals were very expensive (the cheapest in 1975 were typically over $1,000) and print based terminals, such as the DECWriter, weren't much cheaper, if at all.

As a result, many hobbyists turned to surplus teletypes as input/output devices. They were usually fairly inexpensive and were reliable enough for their intended use. They also had the added bonus of providing paper tape storage for information retrieval at a "blazing" 110 baud (about ten characters per second or about 5 to 6 typewritten lines per minute)

The full ASR33 Teletype on the pallet showing the unit, stand, paper holder and a box of ribbons

Pictured above is my ASR33 as it arrived. It was probably a military surplus unit returned to the depot in need of repairs. The ASR33 (Automatic Send/Receive) was strapped down to an ASR35 pallet with genuine old stock tie-downs. There was tape in various places to hold the whole thing together. It looks to have sat in this condition for at least 25 years.

Strapped to the pallet is a hard to find document holder and to the left is a box of ribbons for the unit.

A closeup of the ASR33 teletype keyboard and keypad

Here is a better view of the keyboard and keypad. The paper tape punch/reader can be seen to the left.

The ASR33 Teletype serial number plate

The date code of 28 69 indicates that this unit was built in June of 1969. The stand contains the phone set/modem and is dated 1970.

A rear view of the ASR33 Teletype with the cover off showing the motor and inner workings

After undoing all of the dried old tape and straps I was able to get the cover off for this interior picture. The main motor is easily visible in this rear view.

A front view of the ASR33 teletype with the cover off showing the inner workings

Here is the front of the uncovered unit with almost everything but the keyboard and teleset guts exposed.

Shortly after snapping these pictures I was able to power the beast up. After a few quick adjustments I was able to get the machine to sort-of work. The pad on the typing unit has gone soft so the typed output isn't quite readable and there will definitely have to be some cleaning and reforming done to make this machine work properly.

After that and a little cleaning and this unit will be hooked up to the Altair 8800 to give a taste of cutting edge personal computing from 1975.

After sitting for some time I finally got back to working on this unit. I've managed to replace the typing hammer and got the machine to mostly work. At this point about every tenth character types incorrectly both on the paper and on the paper tape. Either the cam is worn or there is something else that I can't yet figure out wrong with this unit.

Help is hopefully on the way.