a setback

 Well, it's clear now why the K|s2 body was such a bargain. It is already possessed by the defective-solenoid issue that is Aperture Block Failure.

definite underexposure..

It's the demon of the Pentax world, and has wrecked the reputation of the Pentax midrange line since the K30 and has mostly been addressed by the K70. Worse than this - it forces users to buy earlier models to steal the Japan-made solenoid which hastens the early models' demise as well. Hence the high number of 'for parts only' bodies for sale on eBay. 

The single-digit bodies starting with K-7 use a different method to push the aperture lever for proper exposures. For other models including the K|s2, a solenoid fails far too early in the camera's expected life - and the result is all shots are taken with the aperture fully closed. 

Sample: metering at f/4 is done correctly but shot is taken at f/32 = resulting image is both six stops too dark and subjected to diffraction effects at the lens' minimum aperture. If all your metering is done at f/16 you're only two stops underexposed, but diffraction still yields an image with limited resolution. 

Yuk! 😱

Here are consecutive shots, one in normal shooting and one in live view. These are at f/9 with auto ISO - note the underexposed is iso5000, the live-view is 51200. I'm not sure how I got to that number as I thought autoISO was set to top at 8000. Clearly I need to lock down a few other parameters and try again. Not also this is with firmware 1.0; perhaps changing that will yield different results, but perhaps not.

Here's another shot that is overexposed and ISO is pinned at 8000 - so perhaps between these shots is when I adjusted ISOmax. Still not helpful since I have no similar shot in normal mode.

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I fully intended to return the camera - but life has intervened and I won't be able to do that in time to meet the seller's deadline. I therefore have two options: 

• send in for repair (doubling the camera's price, and likely getting an improved but still inferior K70-era solenoid) or 
• find a donor body and do the work myself. With no spare time right now that could take a while - but I have a K7 in hand so am not desperate for a perfect K|s2 in a hurry.

I've gone with option two, and have picked up a functioning K100d body +18-55mm lens for under $100. Most K100d bodies have two fully-useable solenoids, one on the flash circuit and one for the aperture. In that case I can steal from the flash and still have a working K100d to keep or pass along w/an external flash! Many Pentaxians have done this surgery and posted all the instructions, so if I take my time it should be fairly straightforward.

This brings the K|s2 price to about $360 plus labor, which is a decent price for the feature-set. A 20Mpix stabilized sensor, weather-sealed body with bonus features (pentaprism, flip screen, many famous Pentax features) and one that uses my current set of lenses as they were intended. 

I looked at other options, but this seems the best solution right now. Jumping to other brands could bring me most of these features other than autofocus, but under the budget and circumstances I'm happy with this decision.