The $10 SP 1000

Nesster · Expire: 2014-02-20

The shutter is capping and dragging... on my cameras this tends to happen a) in the cold b) at high shutter speeds. The shutter may just need to limber up after all those decades - shoot with the empty camera at all speeds, a lot - or it may need a shutter cleaning and lube.

I'm finding the majority of my Pentax mechanical shutters are in need of a CLA - they cap in conditions a and/or b.

peterqd · Expire: 2014-01-04

It's difficult to be sure without inspecting the camera, but to me it looks probably as though the first shutter curtain is a little sluggish to get off the mark. This causes the second curtain to catch it up and results in what is called capping, when the gap between the two curtains is either zero or at least far too small, and the result is underexposure. The banding in the last two shots is a typical sign.

This is a very common problem with old cameras and is often erratic, some frames are OK, others not. Very often it clears itself after some exercise - for example:
http://www.flickr.com/groups/spotmatic/discuss/72157605851923697/

If it won't cure itself, you'll need to clean and lubricate the shutter curtain bearings. There are 4 in the base and 4 at the top. The bottom ones are easy to get at by removing the baseplate but the top ones are awkward - you have to remove the top and then other components to see them. Often a CLA on just the bottom ones will do the trick because these collect more crud. Clean the bearings by applying lighter fuel several times and working them, and then allow the solvent to dry thoroughly. Then lubricate with a very tiny touch of light oil on the end of a fine screwdriver or even a needle. I use valve oil meant for the piston valves on brass musical instruments, which you can buy in any music shop selling brass. Light sewing machine oil is OK for this too.

Under the baseplate you'll also see the tensioning screws for the shutter curtain springs. These are locked with a red lacquer. !Do NOT be tempted to touch the tensioners! - they're set in the factory and readjusting them is a PITA. Smile

rukmeister · Expire: 2011-11-18

Thank you so much for the information Very Happy

I know the 3 lenses i used were fine - they've been cla'd and the underexposed shots are randomly scattered through the roll - happened with all the lenses.

What you're saying makes sense to me. The rest of the shots came out ok, but some do seem a touch underexposed too for what I intended (and the meter gives me very close readings to what my SD14 dslr gives on centre weighted with same lens etc so i'm pretty confident the meter is still ok)

When I have time I might do top and bottom, then I can find out for sure what's going on with the veiwfinder at the same time.

Nesster · Expire: 2014-02-20

Yes, the two typical symptoms are present in your samples - the dark edge band, and the random darker band in the middle. The slit movement in the shutter becomes erratic over the full frame. Thanks Peter for the cleaning/lubing info, I might try that on some of my cameras rather than sending them out to be worked.