Thank you! I had considered one of those replacement lenses from eBay but put that idea on the back burner at least until I finally dismiss this lens as unrepairable. And interesting the thread in your 2nd link indicates that some such replacement lenses are actually factory rejects. I might do better to wait for a non-functional SX200 with a different fault to come up on eBay, and then I should be able to get one working camera out of the bits.
Sadly lens damage is the most likely fault (with LCD damage being the second most likely one), and therefore you may have to wait a while for another SX200. Having said that, you may well pick one up with a damaged LCD for not very much, so long as you are prepared to wait. I set myself a goal of never paying more than £4.04 (+P&P) for any camera, and I have collected a substantial collection over the years.
The lenses you see on ebay may well in fact be "recovered" from e-scrap, I've bought a few over the years, and only had one dud (it had dirt in it).
Wow! That thread is impressive! My lens is substantially different, but as you say, the principles are very likely to be the same. In particular, my guess that there is a stow switch to indicate when the lens is retracted seems to be correct, but I'll have to read it much more carefully next time I have my lens out.
The optics and sensors vary, but the basic mechanics and position sensing electronics are typically very similar. The pinouts of the ribbon cables are also generally very different in their layout, since they are designed for easiest assembly of each particular model.
One particular point you can probably help me with: it says some opto switches are held in with rubber cement. I seem to have several of those such as in the attached image. I wasn't sure whether you could remove them or if so how, with the result that I've been putting more strain than I like on the ribbons, so farwithout obvious damage. Presumably you just scrape the cement off. But what sort of glue do you use to refit them?
Regards - Philip
Fixing the lenses is a bit of an art. I can't give much specific advise, apart from the fact that cyanoacrylate (superglue) is not a particularly good idea as it tends to fog optics. Bathroom silicone sealant applied very carefully with a syringe or needle makes a good substitute for the rubber glue, ( mix it with a little talc or cornflour if you want it to set quickly). Bathroom sealant however produces acetic acid, so use it sparingly, and try to avoid getting it on metal parts. The plastic of the FPC ribbon cables wont care, but copper contacts probably will.
Removing the various glues takes patience, and if you have a good magnifier or access to a microscope that will also help. The magnification doesn't need to be particularly powerful, x 4, x10 or x 15 will be more than adequate for most tasks. Also look out for plastic anchor pegs that go through small holes in the FPC cables, you will need to lift the cable off these pegs before attempting to extract the sensors.
One other trick that Canon use in some models is to solder sensors and sections of the FPC cable at different parts of the assembly process, to allow for more complex folding and tighter cable runs. This means that some lenses can only be disassembled by un-soldering certain contacts. Soldering these cables requires a very fine tip on your soldering iron, and careful handling.
As far as removing the glues goes, I tend to use a very small flat bladed screwdriver, or a scalpel blade, and light pressure, you don't want to cut through the tracks on the cable.
One final point, I spent a lot of time trying to figure out why one of my lenses didn't work, only to discover that there was dirt in one of the connectors on the main PCB, and nothing actually wrong with the lens at all, so check that your connectors are clean and that the cables are straight, and correctly seated in the connectors.
