[GreenKeys] More 28 Typing reperf trials & tribulations - typing

[Nick England]

I am sending this so it'll get stuck in the archives and maybe be useful to
someone else some day.

The patient is a 60 year old Model 28 typing reperforator (LPR). The
patient presented an inability to print the correct letter on the tape much
of the time. The holes were being punched correctly so the selector, etc.
was working fine.

Axial positioning of the typewheel was wrong. The Axial Sector was removed,
the Cylindrical Rack (moves the typewheel in/out) was positioned correctly,
and the Axial Sector replaced. (n.b. Push Bars 1 and 2 rotate the Axial
Sector to position the typewheel at rows 0, 1, 2, or 3.)

But the rotary typewheel motion (Push Bars 3, 4, & 5) was also jittery.
In the resting state, the typewheel would sometimes be in the correct home
position (T or 5) and sometimes rotated off by one character. The typed
characters were mostly garbled.

The problem with rotary positioning of the typewheel was indicated by the
Left Eccentric Assembly not being positioned fully up and fully down by the
Letters and Figures Push Bars. This caused Push Bars 3, 4, & 5 to sometimes
correctly move the Typewheel Rack (which rotates the typewheel), but mostly
not.
The cause was the Push Bar teeth being out of position on the outer gear of
the Left Eccentric Assembly. This is very similar to other problems I have
encountered with  Push Bar to Eccentric alignment and which has resulted in
much wailing and gnashing of teeth.... until I got helpful advice from some
experienced greenkeyers.

So I followed their advice again and pushed/whacked the Push Bar so it
skipped over a couple of Eccentric gear teeth and landed in the proper
place. In this case, I removed the ribbon assembly and uncoupled the Left
Connecting Rod from the Left Eccentric which made access and "adjustment"
much easier.

After reassembly, the QBF is jumping merrily over the LDB and Letters and
Figs are behaving themselves. Those Teletype Corp. engineers were
fiendishly clever. And greenkeyers are a great and helpful bunch of folks!

Have Fun!
Nick England K4NYW
www.navy-radio.com
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