Regular readers will recall that back in early 2020 my Pentax K50 DSLR developed the dreaded “aperture block” fault and that I repaired it by replacing the faulty electromagnet with one purchased on eBay. Readers may also recall that sadly this was a short lived repair and that the problem returned a little over a year later.
Investigating the issue online, I came across this extremely useful post. The first half explains how to replace the magnet, which I already knew how to do, but the second half is more immediately useful as it considers various repair strategies. The bottom line is that there is only one way to effect a permanent repair and that is to replace the failed green magnet with a white magnet taken from one of Pentax’s early DSLRs.
Convinced that this was the only viable solution, I began looking for a suitable donor camera. I asked a few people I know without success, and in the end found a none-functioning Pentax K-x being sold on eBay “For parts”. I managed to get it for £28 including postage.
The K-x contains two nominally identical magnets, one to control the aperture and the for the less demanding task of releasing the pop-up flash. I started opening up the K-x and tackled the flash magnet first, but this turned out to be a green one. Apparently all K-x cameras have a white aperture magnet, but the flash magnet varies. Sadly, I didn’t realise it was green until I had removed it.
I then turned my attention to the aperture magnet and – much to my relief – it was present and white!
With both magnets removed it was possible to compare them. As you can see, they are superficially very similar apart from the type of plastic used, but there are a number of small differences in construction and materials which seem to drastically affect their long term reliability.
Finally, it was possible to gingerly dismantle my camera and fit the white magnet. I was very relieved when a few test shots showed that it was once again working. I also re-assembled the K-x which I hope I can now sell on to someone else for spares although I’m sure to get less than I paid now that both magnets have been removed.
