Saturday, October 25, 2014

Console printer working correctly, plus minor work on keypunch interface and card reader


I worked the various levers, pawls and other parts of the carrier that are involved in escapement (spacing) and tab operations. As part of my investigation I noticed a crack in the carrier string pulley on the right side that maintains tension on the cord. To remove this as a cause, I replaced the part; no change in the behavior but better to have a good part in place.
Part with crack in white part, front left

replacement part that I installed
Interestingly, the mis-spacing occurs in the same spots, which implies some friction, bent parts or residue in the racks into which the pawls engage. I don't expect to find bent rods, but perhaps there is sludge on surfaces I can't see that are impeding the operation. If I hand-cycle the typewriter after pushing the space button, at the columns where I have problems, I can see it either fail to move at all or move half a column.

The half-column movement can be caused by the backspace pawl and escapement pawl being out of adjustment, so that it sometimes stops at the backspace rack tooth (half-column). I originally attributed this to sludge between the pawls which slide over each other and around any pivot arms. I have worked so much lubricant through this area that I am losing faith with the sludge hypothesis.

Another failure mode, also occurring in the same area of the machinery, is the failure of a tab operation to latch, which is necessary so it can slide rightward until a tab set tooth releases the latch. It is bouncing but not latching, resulting in a skip of a few columns - but not tab set exists at these locations.

Later today I worked the pawls some more, ensuring they all slid easily and independently. Now, with power applied, the spacing and tabbing seem very consistent. So good that I am going to close up the typewriter cover and consider this restored. Patience paid off.


The cornering station and ability of the stacker feed rollers to take the card away remain a problem. I did more cleaning, tweaking and attempted to adjust the pressure rollers for those stacker rollers. So far, it is no better. I was able to boot the cold start card from the reader and it appeared to be correct in core. There is a check condition at the end of the read but if the data got in correctly, I have to assume the problem concerns slowness in the card movement due to residual sludge. With patience, this will be corrected just as with the console typewriter.


With the interface cabled into place, the keypunch is being cantankerous about recognizing a registered card, sometimes leaving the keyboard locked so I can't punch on the card. Removing the cables restores the keypunch to normal operation, which means the cause is something happening within my interface box.

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