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Sunday 10 November 2013

Removing and Replacing the Platen on a Series 3 Corona Portable Typewriter

In a comment to my previous post, on fixing my green Corona portable typewriter, Richard Polt asked for some tips on correctly replacing the platen. I know exactly what Richard means when he says that the action can become stiff after putting the platen back in. I doubt whether I will be able to tell Richard anything he doesn't already know about this tricky process. However, I'd almost be willing to beat money that the problem he has encountered is with the metal tray which holds the feed rollers under the platen, and ensuring the smaller, bottom feed roller is correctly in place.  My experience is that this roller has an all too-ready tendency to pop out of place while you are thinking of, and doing, half a dozen other things in slotting the platen back into place.
Because of the difficulty in making certain that the studs of this feed rollers plate are in place when slotting the platen back in, I would suggest that this whole operation is really a four-handed job. Normally I wouldn't tackle anything like this in the absence of my son Danny. He is a bit of a wizard when it comes to putting platens back in typewriters, and with him being away this weekend I had to take on the job on my own. Not exactly a big mistake, but I am sure when Danny gets back tomorrow morning the operation will become a lot smoother. 
In response to Richard's request, I took the platen out once more to photograph the process of removing and replacing it. In doing so, I did notice that the bottom feed roller had again moved out of place, although this may have happened as I removed the platen a second time. It is definitely something to watch out for. There might be a way of tightening the grips, so that the smaller feed roller stays put during this operation.
Anyway, here is my photographic essay of the whole exercise, not one that I enjoy doing on my own very much. Most platen replacement operations require, at least for a layman such as myself, four hands, and I think that is particularly so with typewriters such as this Corona and the Imperial Good Companion. One warning - I noted when looking at my Series 3 burgundy Corona (Sterling) that the left-side platen knob arrangement is much different, and even more complicated than on this green machine. So be prepared to find different set-ups with different Series 3 models. I suspect the arrangement on my green machine is, if anything, the simpler one.
Anyway, as I said, I don't think this will of much help to Richard with the Corona he is working on for WordPlay, except perhaps for the feed roller plate - and fitting the platen back in while ensuring this plate stays in place is really not a two-handed task. On mine, any very slight movement jolted the smaller feed roller out of place. Still, these images might be of some help to others tackling this onerous undertaking. Please understand that I am no typewriter technician and have never pretended to be one, but am simply illustrating what has worked for me. I am expressing this in my layman's terms, so that hopefully it is easy to understand and follow.
It's always an excellent idea to take a very, very close look at how the mechanism fits together BEFORE dismantling it. Maybe even take a photo to refer back to, or make some drawings. Here you will note that, in the absence of my son Danny, my typewriter guard cat Charlie has volunteered to help, but at the first utterance of a swear word, he turned his back on me. His rump can be seen in these photos.
Bear in mind that even a top-line expert like John Lavery can sometimes encounter difficulties: John once asked me to photograph the lever turning mechanism on an Olivetti ICO MP1, to help guide him in fixing one of his typewriters. As John said at the time, this particular mechanism was "over-engineered", making it more complicated than perhaps is necessary. Certainly the platens on later Olivetti portables are far, far easier to remove and replace.

The centre rod of the platen should be removed from the left, with the left platen knob still in place. To remove the rod, you must undo three screws on the right. I always find it a good idea to undo the screw holding the knob itself to the rod only as far as necessary to take the knob off, and not take it out completely. They can sometimes be difficult to screw back in. The two screws holding the rod to the platen core are very small. Be careful to use the right size of small screwdriver, and not apply too much pressure when re-tightening, or the top section can easily chip off. When that happens, it is necessary to use a fine-nosed pair of pilars to get the screw out, but this should be avoided.

 Oops! Bad news. New screw needed
This is one of those platen knob arrangements in which (when the machine is back fully operational) pulling out the knob frees the platen from the line-spacing mechanism and allows the platen to turn freely. Take careful note of how the metal part attached to the left knob fits into the platen core, for when you are putting the platen rod back in from the left. The platen core will have an opening shaped to grip this flattened surface.
These two clasps fit inside the platen core. They sit loosely, and are not held in place by anything. It is tricky to position them so that the main cog of the platen slots back in between them. Because they sit loosely inside the core, one or both are more than likely to fall out when removing the platen. Be prepared for that to happen.
 The main cog.
 Positioning the clasps, ready to slot the cog back in between them.
Gently push the cog back in at a slight angle. One side of the cog will fit in under one clasp, and then with a tiny amount of pressure the whole cog will sit down flat on the end surface of the platen. Keeping the cog in place when replacing the platen once more emphasises that this is really a four-handed job.

When removing a platen from any typewriter, I always use one of those plastic-coated wire tags that come with most electric appliances, tying the power cords in a bunch. When I buy one of those items, I always put the little wire tag to one side to use on typewriter jobs. It may not be super important, but for me it helps keep the various parts of the platen lever mechanism in correct order. It won't keep them in the right position, but I find it does help.
On this model, this small spring-held rod on the lever turning mechanism sits on top of a metal tab. When you remove the platen, the whole mechanism will drop down, even when using a tag. When you are positioning the mechanism before replacing the platen, all of this will need to be lined up correctly, and held in place, otherwise the turning mechanism will not work.

Where possible, I have found it a good idea to pull in and hold the platen lever, so that when the platen is replaced, the mechanism is ready to engage properly with the platen cog.
Now we come to what on this model is the really tricky bit. On most machines, getting the feed rollers plate to sit properly is seldom a problem. With this model it is a worry. As with most machines, the plate is held in place by two studs which slot into holes in the carriage. It may be because of the position of the paper plate, but I found that keeping the feeder rollers plate and the bottom roller in place through the platen replacement operation most difficult. The plate kept wanting to move out of place, and, as I said, even the very slightest of movements pops the bottom, smaller feed roller out of its grips.

Looking at another of these models, I became aware that lining the feed rollers plate up with the paper plate provided a very good sight guide in ensuring the feed rollers plate is correctly positioned. The two plates will line up squarely, obviously, and visually are almost touching one another. The top edge of the feed rollers plate should be seen to fit right up against the bottom edge of the paper plate, but not to slot in underneath it or sit slightly in front of it.
From sorry experience, I must stress that it is vitally important, when fitting the platen back in, to take extra special care to make sure the paper supports do not get caught under the platen and are pushed in and/or down by the platen. You might feel you need more than four hands in this situation, as the paper supports are spring loaded and unless held back to allow the platen to fit back inside them, and the printing point guide, you can cause irreparable damage to your typewriter.
Now comes that extremely delicate operation of slotting the platen back into place, ensuring at once that the platen turning mechanism and the end cog are all held in correct position and lined up so that the left platen knob and platen rod will slot back in and the carriage lever will work properly. You have about half a dozen different things to think about, and do, at this critical point.
Give yourself a very good idea beforehand about how the left knob slots back into position.
And most important of all - GOOD LUCK!!!


Bill M said...

That is some very detailed work. Thanks for the excellent description of the work and your excellent photos. I do not own a Series 3 Corona; yet.

As often happens I will see a fine typewriter on your blog and somehow I end up with one.

This is one post I am going to bookmark for future reference. It is superbly excellent.

Scott K said...

Nice one Robert!

Richard P said...

Oh my god -- this looks tough! Thank you very much for documenting it and sharing your experience. Doing this and taking photos must be a FIVE-hand project.

I can see that the Corona I'm working on is different in at least one way: those "clasps" do have something holding them in, something like a wire. (I don't have it before me.)

Later Smith-Coronas were super-easy to work with: the platen just pops out and pops back in. I did not expect the early ones to be this bad.

Thanks again, I will tackle my machine again soon.

Yaru L said...

Thank you for such a detailed description of the process!

rino breebaart said...

Leave it to the experts, I think! When's your shop opening, Mister Robert?

nat said...

Ohhhhhh my goodness. I'm just fiddling and cleaning a Corona 4 now and I got stuck at the carriage assembly. This post is scaring the bezjeebers outta me, but the detailed work is fantastic!
I must now ask the silliest of questions: is the Series 3 Corona have the same assembly as the Corona 4?

Rob Bowker said...

It does make me relieved that I have a quick release platen on my Canada-built Corona Silent though I remember the fun and games (and swearing) I had swapping a bare wooden platen out of a 'parts' machine black Corona 4 into a much prettier blue version. I sometimes use rubber bands to temporarily hold things like paper fingers out of the way or keep a type bar raised if working on the ribbon vibrator. Ace walk-through of a tricky process, especially taking photos at the same time!

Grams said...

Just found your blog and this was pretty much the help I need for a 1934 Smith-Corona. However, my question is...when you removed the platen, did the cog some off with it? If it didn't, how did you separate it from the rest of the carriage return equipment? I just plain cannot find any screw that holds the cog in place with the rest of the carriage return. The cog looks like it could just slide out, but I don't want to risk this until I know what I'm doing. Hopefully, you can help.

(I hope I've explained by situation...when I removed the platen, the cog stayed. The end of the platen has the 2 "teeth" and won't stay in place to slide them back over the cog.)

Saul said...

I have a Imperial Good Companion and the small feed rollers were not gripping the paper at all, they were shot and covered in flat spots. So I had to go into this machine to get to them, and to try and re-cover them with something similar. Just taking this thing apart was a nightmare, so putting it back together -- well, that is a future me problem. Sorry about that, future me, I really am. Try and grow some extra hands in the mean time.

I did want to say how important it is to take photos of the unit as it is, before and during take apart. Those bits near the ratchet are spring loaded and come apart almost as soon as the main roller is off. I can solve a Rubiks cube, but those three pieces would have stumped me without pictures.

My tray was also held in place on the right by having the metal tab twisted in place , and with a fiendish spring on the left. Apparently something like a screw was too easy. Maybe this was a hack by a previous repair, although I don't think so.

Anyway, thank you for your guide, it helped me at least as much in know what some of the likely pain points are/were. Forwarned is forarmed, as they say, although four-armed might be good here too.