Last weekend I brought home a nonfunctional Olivetti Praxis 48. I was able to make some progress on the machine, but I needed to get the carriage shell off to find out more about this mysterious piece of cord that was bunched up under the carriage:
This was the point where I had left off with the carriage housing still attached:
Removing the Carriage Housing from My Olivetti Praxis 48
This past week, I worked on getting the shell off the Praxis carriage. To get the housing off, I first popped the small covers on each side of the platen off with the aid of a large screwdriver as lever.
I popped out the platen by raising the retaining bars on each side.
I lifted out the metal paper pan. The blender watches with interest from the sidelines:
I removed a underside screw on either end of the carriage housing:
and popped the main housing off:
Ah-ha. The housing finally off, I saw what my problem was. The Praxis has two cords: a draw string attached to a mainspring and a carriage return string attached to a return wheel apparatus. The carriage return cord was bunching up and not winding onto its wheel because the carriage return wheel was stiff with gunk.
Once I saw what was happening under the carriage housing, I was able to straighten things out. I applied degreaser to the carriage return wheel and gently moved it with my hands until it felt looser. I depressed the carriage release button and moved the carriage back and forth until the carriage return cord began to wind smoothly onto the wheel.
I used Lectra-Motive to loosen things up. I read (after the fact) that while Lectra-Motive is a wonderful electric parts cleaner, it will eat plastic. I ran out to the garage in a panic and wiped all the internal plastic pieces down carefully. There is a surprising amount of plastic inside the machine guts of the Praxis. No harm done, but I will be more careful next time.
I was struck by how similar the electric 196X Olivetti’s problems were to the problems faced by my Foster Typewriter, the 1938 Royal KHM. Disuse and congealed gunk are the bane of typewriters no matter the vintage. The KHM came to me with a stuck carriage. Its draw string was tangled up under the carriage, and the mainspring was frozen with congealed grease. Once the draw cord was straightened out and the mainspring coaxed back into springy life with PB B’laster, the KHM’s problems receded.
The Praxis had a very similar story: a tangled cord and a stuck carriage. Once the carriage return was loosened and winding properly, the return cord behaved itself. I plugged in the machine and tested it. Wonderful. All the keys were responsive, the carriage was advancing, and the carriage returned beautifully.
Malfunctioning Tabulator Brake on My Olivetti Praxis 48
The major remaining problem was tab operation. When I hit the tab bar, the machine locked up and the carriage froze.
To release the carriage, I wiggled the plastic piece in the back and the machine resumed happy function.
I identified the round plastic piece as the tabulator brake drum. Inside the drum is a set of plastic gears.
The tab brake slows the carriage down during tabbing so that the machine doesn’t slam into tab stops.
When the tab bar on the keyboard is depressed, the top pinion gear engages with the rack:
Once the tab stop is reached, the pinion should pop up free of the rack.
My tab brake was engaging but the gears inside the drum were not turning and the top pinion wasn’t popping up once it hit the stop.
My feeling was that I had a dirt and gunk problem in the tab mechanism. I carefully applied PB B’laster to the metal tab brake parts and worked them with my hands. The gears were initially stiff, but loosened enough so the the brake gears turned and the tab mechanism moved freely. The tab mechanism finally worked as it should, braking gently with tabbing but not locking up.
I made good progress on the Praxis this past weekend. Now it is time to put the shell back on the machine. But first, lunch.
It was a pleasant afternoon so the Praxis had lunch outside with friends:
Stay tuned for the electrifying conclusion of the Olivetti Praxis 48 story.