I finally sat down and performed two camera surgeries - and both turned out very well! A few hours of delicate work has paid off.
First up was the Pentax K-s2. I bought this a few years back for a great price, only to find it had the dreaded Pentax mid-level body solenoid problem. For several years they put out great cameras that began failing after a few years, sooner if the camera went unused for a month or two. They put out a new body by then, but in a few years the same happened. It turned out their source for aperture-actuating solenoids, causing the camera to determine an exposure but then shooting with the lens fully closed, leading to extremely dark and diffraction-softened images.
This problem damaged the reputation of every midrange body from K-30 to early K-70s, including the K-59 and two k-s2 models. The K-5/3/1 models did not have the problem. One could work around the issue with older lenses in Manual mode, but it wasn't ideal
The answer has been to either scout for original cameras to steal the earlier sensor or now using the Kf solenoid. I bought the elder solenoid and .. dithered. Maybe three years passed before I finally did the work today.
Two hours later, all my lenses are back in play. Hooray!
I'm very grateful to those at Pentaxforums who went before me and documented the procedure for all the affected cameras, including the K-s2.
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After dinner I decided to fix the GX7, an old Lumix favorite with a bad rear control dial. That's also rather common, and the surgery is documented on several websites. This went a bit faster (no soldering needed) and thankfully it's problem is solved too! That rear dial serves many purposes, and now it controls exposure, clicks for exposure compensation and zooms in playback mode!
Now to decide between the GX7 and EM1, two very good old μ43 bodies that fit me well. The K-s2 probably won't dethrone either of them or the Sony a7r² ..but I'll keep using it a while to ensure its full recovery before deciding its fate.