[GreenKeys] M15 Restoration -- Type Bar Basket

[Paul Birkel]

Status Update:  I've been earning my wings, but it's not been easy!  After
several repairs I've reached the point that the type bar basket appears to
be operating properly in all respects (and the imprinting looks very good
after a careful cleaning of the individual type bars).  Driving the type
basket properly is another matter, starting with a "rapid unplanned
disassembly" (RUD event) as the cotton cord on the CAR RET mechanism failed,
ejecting one end for parts unknown :-<.  It's somewhere close by (I heard it
land) but it will be many months before I'm likely to uncover its landing
site.  Temporary replacement cord now in place.

 

The CAR RET partial return to the ~10-char position was being caused by a
cracked lever.  Now with a so-so fix.

 

CAR RET initiates erratically, and possibly related to the consistent
behavior that actuating _all_ keys (including FIGS, LTRS, and BELL!) result
in double-move of the type basket, the first without any printing
(equivalent to the BLANK key) and then the second with the correct
character, when applicable.  This seems like a really odd failure mode to be
caused in the base mechanism.  I remain suspicious of the keyboard emitting
two cycles rather than just one per keypress.  Or perhaps the selector is
cycling twice for reasons of its own.  Lots of hypotheses ..

 

Anyone encountered this behavior on an M15, M19, or perhaps even elsewhere?

 

From: Paul Birkel [mailto:pbirkel at gmail.com] 
Sent: Wednesday, February 03, 2021 2:30 PM
To: greenkeys at mailman.qth.net
Subject: M15 Restoration -- Type Bar Basket

 

I'm in the process of bringing an M15 back into service after a long period
of storage.  This is the unit that was previously used by a MARS member that
I've mentioned in previous queries.  The dash pot is now unfrozen and I've
been able to set up a local loop.  I'm using a REC11, so plenty of loop
power; the loop is currently running at 62 mA.  The resulting behavior is
not yet explicable.  As this is the first green keys "recovery" that I've
attempted I can use a bit of guidance!

 

The general behavior is that the selector unit and vanes appear to be
responding correctly to the keyboard.  FIGS and LTRS shift/unshift the type
bar basket properly (controlled by the bottom vane) and the (FIGS) BELL key
works.  Other keys work, but with sometimes incorrect results (although in
most cases given the lack of printing it's hard to discern beyond obvious
consequences like a SPACE resulting in a CAR RET).  The principal behaviors
are that:

 

1.     No type bar is ever triggered, nor does the ribbon advance.  The type
bars are all freely moveable.

 

2.     Key presses appear to advance the type bar basket double; 38
key-presses advance the basket across the full width of the platen and then
further key-presses have no effect.

 

3.     CAR RET causes either a full return, or a partial return to approx..
the 10-char position (in which case a second CAR RET returns the basket to
full-left).  It's always one or the other.

 

4.     LINE FEED usually works, but not always.

 

I notice that the PULL BAR BAIL floats forwards-and-backwards rather than
being held firmly against the front PRINTING BAIL BLADE.  This doesn't seem
right to me.  Perhaps I have a lost or incorrectly positioned spring
somewhere?

 

The PULL BAR BAIL behavior, what appears to be double-advance per key-press,
and the lack of ever triggering any type bar, seem to me to be the key
anomalous behaviors.

 

I can imagine that there may be a timing problem (or perhaps related
lubrication problem affecting vane control) resulting in erratic behavior on
a per-key basis (even the space is erratic, sometimes causing a CAR RET),
but I'd like to first get "basic operations" functional before probing
further.

 

I have not at this point attempted to clean and (re)lubricate any mechanisms
beyond the dash pot.  I absolutely want to avoid major disassembly, unless I
have no other option.  I don't trust myself to get it reassembled and
adjusted properly afterwards!  I do intend to go over all of the lubrication
points once I'm closer to working order.

 

Do I need remove the type-bar carriage, invert, and check/lubricate
everything there before proceeding further?  I don't think that would affect
the double-advance per key-press behavior, but I have much to learn.

 

I do note that it seems as of the motor generates a lot of ozone.  But it
sounds completely normal to me; hums right along.

 

Your thoughts?  I'll keep studying TM11-2215 .

 

Thank you,

paul

 

 

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