To remove surface rust and rather a lot of dirt in the segment slots, the typebars were taken out of the machine. To take out typebars, the fulcrum rod has to be taken out of the slotted segment.
This rod is usually fixed with one or more set-screws - in the case of the Corona there are four small screws distributed over the segment arc right between the typebars. Tricky to get at, but they only need loosening half a turn or so.
Because the rod probably is stuck and needs to be pushed out of the segment, pushing or tapping it with a chaser rod probably is the best (only) way. From an old knitting needle a chaser rod is bent, plus a shorter straight rod for the final pushing it back later. The diameter a little bit smaller than the fulcrum rod.
The typebars are then cleaned in the usual manner - scrubbing with steelwool, followed by a good scrub in warm soapy water. (Essential to remove steelwool debris!) Much cleaner typebars:
The typebars are numbered, as is usual. As is also quite common, there is one mis-numbered typebar! There are two #20's and no #18 typebar - they probably ran out of #18 at the line and bent a #20 to make do. A nice touch is that the 6 and 9 typebars are underlined to reduce confusion on which is which:
The segment was also taken off the machine and given a deep clean too. If it can at all be avoided, this is something I'd try not to do on a folding Corona. But in this case it was very dirty and to not risk the red finish of the machine, it was unscrewed and taken off.
Re-assembly is the reverse of dis-assembly, as they say. That is true, but for the folding Corona a tricky affair - quite a challenge to fit the little push-rods and maneuvre all typebars back into their slots. Tweezers and patience.
The short straight push rod comes in handy to drive home the fulcrum rod to its proper position.
The segment was taken off; placing this back is however a bit tricky on the folding Corona's. In the factory they'd have had a jig fixture to help with this. Because there is no baseline or on-feet adjustment on the carriage of a folding Corona, it is very likely that there also was a working instruction from Corona for typewriter repairerers. Not having either of these, we improvised.
Careful half-tightening of the four screws that clamp the segment between the typebar-rest-brackets and the back-plane allows careful up/down adjustment of the segment position.
With the segment not-quite firmly fastened, slide it up to the highest it will go; the top-most position. Testing then with the centre typebar (e.g. the 'B') and a left- and right-typebar, see how the slug enters the typeguide. It should not touch either side of the guide; if it touches the right side of the typeguide, then very gently push down the left-side of the segment a very small amount.
Jockey the sides until all typebars freely enter (and exit) the typeguide. The segment is properly horizontal then, relative to the carriage. The typing may then still be bottom-heavy (or top-heavy). In case the writing is bottom-heavy, i.e. the characters are darker (bold) at the bottom, then the whole segment is too high relative to the platen.
More careful jockeying the segment down is then needed to get the 'on-feet' adjustement right. Both sides given a very small downward nudge, keeping the horizontal alignment - i.e. all typebars still move freely in the typeguide.
This all worked, but seems a convoluted way to re-position the segment and do on-feet adjustment - there must be (have been) a better way - curious for suggestions and please do share if anyone finds the factory instructions for the baseline adjusting of a folding Corona. typewriter!
