When looking at the relationships of the out-of-whack type bars, with all of the other pivots and stops and springs and the stresses imparted when pushing the type bars down, I decided to dig deeper.
I had heretofore gone through every point on the chassis of the machine to look for adjustments that might have slipped. All of these screws have no room for adjustment, they are precision located and lock their respective member in its exact, intended location.
When the raised type bars were pushed down, the lower edge of the segment would move slightly toward the front of the machine. Was this flex due to a crack? How does one look behind the segment? There's only one way I knew of, so stripped down she goes...
|No cracks here (picture taken B.C. - Before Cleaning - I might add! :) )|
I removed all of the type bars from the segment and removed the segment. I inspected the cast cross member that acts as the segment support... no cracks visible.
Of all the pieces that stressed and moved when pushing down on the raised type bars, the main, cast type bar cross-member was my next suspect.
Again, having no adjustment possible in the mounting of this cross-member, and seeing no visible signs of stress fractures ... what next?
When I would push down on the cross-member and the type bars would drop, I also noticed that the bell crank portion of the type levers that extend from the pivot of the cross-member, toward the keys, would rise and fall. This could be impacted by the height of the keys in their resting positions .... and I also noted that the highest type bars were the furthest row of keys (yxcvbnm,. -- being a QWERTZ keyboard).
I then looked at the various places where key height might be adjusted, and decided to remove the front plate with the slots through which the key bars protrude - they all rest at the top of the slots on this cross-bar:
I first loosened the four mounting screws for this cross-bar, but there was no adjustment possible. I then removed the four screws, and POP ... the crossbar jumped about 1/8" upwards and guess what happened as a result...
Okay, so now what? There is no vertical (or other) adjustment possible in the mounting position of this bar ... so what about the rest at the top of the slots?
Well, here's the rub. There is a plate at the top and behind of this cross-bar, where the key levers rest. There is also a rubber sheet that the plate holds in place, to cushion the levers when they reach the top of their travel.
The top bar of this front panel is riveted in place:
This plate, which I had hoped was adjustable, does not appear to have room to play:
I always try to find root-cause ... the "why" behind the issue, and in this case I can only point to this key bar rest as a suspect, not the cause... and that is because I can see no evidence of damage or change. This stop does not appear to have play for adjustment, and the change would have had to have been in the downward direction - yet there is not visible sign of a bend or stress.
So it's back on the bench with a giant question mark hovering over it. :-( Ideas?