Re-activating column 7 and 8 on the Burroughs Portable adding machine

When entering numbers, all columns seem to work. For example, entering 7777 on the left-most columns makes all segments rise and print as they should.

When then doing a total, the columns 7 and 8 segments do not rise and do not print, but the column 6 and 5 print, as does '*' (total sign) on the right-most printing column.

The print-out confirms that columns 7 and 8 are not working in totals.

That was an interesting fault - when the machine was taken apart earlier, the register wheels were spinning freely; no binding. That they print fine when simply adding confirmed the problem was not in the register itself.

Staring at the operation of the machine (with covers off) during adding and when a total is taken, tracing how the parts move, pointed to the problem being in the keyboard. The differential-bars slide under the keyboard for every column.  In adding it is stopped by the peg of a number-key at the right position to cause that number to be added to the register.

At the front of the machine is a rocking bracket for every column - this is rotated out of the way if a number is entered or when a total is taken. When a total is taken, the differential bar (and connected segment etc) needs to slide all the way until stopped by the register-wheel - that's how the value on the register is retrieved for printing a total.

The rocking brackets for columns 7 and 8 did rotate their 'stop' tab down far enough for the differential bar to slide over them. The columns 7 and 8 were snagged and thus always a zero was registered as the totals-value on columns 7 and 8.

Some more peering at the mechanism revealed that very probably the tab that holds the rocking brackets in the keyboard key-locking-bar was bent for the columns 7 and 8. They were angled slightly different from the rest.

These rocking brackets are exposed when the mechanism is out of the case. Looking at this, actually it's likely that this fault was accidentally created by me when working on the mechanism- perhaps when giving the keyboard a thorough scrubbing to clean the keys, dod not take enough care to not put any pressure on these exposed bits.

Slowly and carefully bending these tabs back so that the differential bar just clears the little stop-tab re-activated the total working correctly. As seen in the print-out of all sub-totals for testing if the bending was far enough - first column 8 re-activated and then column 7 came back too.

Just to be sure, adding 333 and 222 indeed gave 555 back in the left-most columns. 

Feeling confident enough to test the tens-carries; multiplying 12345679 by 8 - that also worked fine and printed the expected answer.

(The printing line is a bit obscured by the ribbon. That's because the machine is now fitted with a standard half-inch or 13 mm ribbon. This fits and works, but the machine is made for a 7/16" or ~10 mm ribbon, just like a Hammond or an Oliver. We'll have to see if a well-inked 10 mm ribbon can be arranged for this machine. Until then, a regular 13 mm ribbon does the job.)

This machine is proving to be a grand puzzle, and very much understandable/repairable - more cleaning and some restoring to do.

:)