Thursday, February 26, 2015

More 1132 printer cleaning, rehabilitation and oiling


Spent a couple of hours working on the printer - freeing up restore latches and ensuring the cam clutch discs rotate. The restore latch bar has one of its attachment screws directly behind the edge of an intermediate drive gear, which prohibits removing the restore latch bar unless I disassemble the drive and quite a bit of the rest of the printer. Going to work on the latches without further removal.

I oiled the pivot points of the print wheel hangers, but it is hard to move them except by rotating the cam clutches. These won't relatch into the idle position due to stiffness in clutch latch levers, which are devilishly hard to reach or work on with the cam clutch shaft in place.

Oiling and moving the restore latches, but a few of them don't pop back out as they should. It doesn't feel like sludge holding them, instead I don't feel the spring tension that ought to pop them back up. It might be dirt keeping some springs compressed, or it might be a spring failure.

The access to the restore latch springs is placed on the side and angled a bit downward, meaning that the latch bar MUST be removed to safely open the access and clean the springs. I am sorting out how to remove the intermediate gear, before removing the restore latch bar.

It worked out well enough to just remove the circlip and the bolt, slide the intermediate gear out partway, which gave me room to pull the teeth of the last bolt free from the bar without the bolt having to come all the way out. I put that assembly aside and looked at the state of the cam clutches and clutch latch levers. The latch levers seem very sticky, obvious from the uneven state they are in right now.

I will do my best to clean these up in-situ, because the removal requires removing the cam clutch shaft, cam clutches, and the print wheel assembly! Basically a complete tear-down, which I don't want to do. I think I can work oil into these and make them perform adequately.

Clutch detente levers at top, restore levers at bottom, plus guide bar on right
I read over the history of the restoration of an 1132 at the National Museum of Computing in the UK - they didn't take the unit apart as I did but their experiences show that it had many of the same sticky levers. At first, some columns wouldn't print or would print repeatedly or slam in the wrong character. Over time as they kept printing on it, the issues sorted themselves out one by one - symptomatic of the sludgy grease warming and clearing out through usage.

I had to open the spring access plate of the restoring latch assembly, clean and oil the springs, then carefully re-install the plate. That was extremely difficult, with 120 tiny springs attempting to bend around the edge of the plate. I was able to ultimately get them all installed and tightened down, work in lubricant across the levers, and ended up with this assembly working perfectly.

My cam detent lever assembly from before still has some columns that don't pop all the way out. I suspect that if I open the spring access plate again, I can get these all working properly as well then lubricate all the pivot points.

Cam clutch discs, with clutch latch levers visible at bottom of disc
Next up, tomorrow, is an attempt to clean and rehabilitate the clutch levers and the print wheel hangers without the total disassembly of the printing mechanism. If I am successful, I can put it all back together and do some testing.

Clutch latch levers, obviously gunked up and sticky


  1. I've never worked on one of these, but I do have lots of experience with dried/gummed grease on Selectrics. I have found that automotive spray carburetor cleaner is very effective at dissolving the varnished oil and grease. Of course, it will damage paint, but is safe for metal and most plastics. Use it sparingly and then blow it out with compressed air and then re-lube the mechanism. It's way more effective than just working oil into sticky mechanisms.

  2. More rapid treatments will certainly work, but since I have plenty of time and can be patient, I prefer to be as cautious and over protective as I can with the mechanisms. I do the same with the 1053 (IO Selectric console printer) because of all the switches and solenoids and wires that are intermixed with the mechanical Selectric stuff. It isn't as immediately satisfying as dunking it in mineral spirits or using spray carb cleaner, but this project is somewhere in between a hobby and an obsession for me.