Friday, May 29, 2015

Tab problem identified, replacing part, and carrier return issue tentatively corrected on the 1053 console printer


The only way to find what was wrong with the tab interposer operation was to get access. I had to remove the mainspring and other parts yesterday, but that had to continue to take off the entire return/escapement pulley assembly with its large plate that sat in the way of everything.

Improved access. The green oval indicates the CR and index latches, the red oval is for space, bs and tab. 
Looking closely, it was apparent that the return spring which pulls the tab interposer backwards when it is released was damaged. It was bent and not exerting the proper pull needed. I will have to find a replacement spring in my supplies (which are pretty large based on having bought quite a few "selectric parts" lots on eBay). Replacing the spring is going to be an interesting challenge, as is reassembly of the parts I removed today. It is akin to laparoscopic surgery, trying to work through a teeny hole with limited visibility and awkward tool mechanics.

Bent spring for tab interposer is visible in the center

I was able to extract the old spring and work out where the substitute will connect. It will be challenging but possible. I began looking through my 17 plastic parts bins and several large boxes of typewriter parts, but a first look didn't turn up the right spring. I need something with about 18 tight turns, good tension and perhaps 5/8" or 3/4" loose length.

I found a suitable spring and invested an hour trying to hook the far end into the interposer eyehole deep inside the mass of levers, brackets and springs. It will be relatively easy to hook the near end, but it is contingent of first attaching the far end.

I did more work on the carrier return mechanism and now have it springing back to full rest position when it is released. Tentatively, the problems are corrected, although to be sure I have two tests to perform - CRs from the Return button while under power, and CRs initiated by a program. In the same way, I will need to verify tab, space, index and backspace by program control and the Tab and Space buttons as well.

I tried for another thirty minutes as night arrived, but still haven't hooked the far end of the spring on the tab interposer.


  1. When I used this stuff I never realized how delicate all the mechanisms were that kept it working. I guess that says a lot for the CEs who kept it all patched together, seemingly effortlessly.

  2. I was thinking the same -- there were guys who worked on selectrics all the time, both in OPD and in DPD. When I was a CE I had nothing but respect for them (and personally viewed the selectric about as I did a coiled rattlesnake). Point is, there is probably more than one of those dudes living within 100 miles of you, Carl. Is there any sort of retired-IBMer forum where you could try to contact one? You might try Dave Bennett at CHM for a lead, he's tied in to the IBM club.