Thanks! It's my go-to SLR these days, especially since I've also now acquired a 58/2 Takumar to compliment it.
I did the curtain replacement myself - I enjoy working on the pre-Spotmatic Pentax cameras, but this was my first curtain replacement on one. I did try to make fresh curtains from scratch at first, using the originals as templates and reusing the AP's curtain bars, but I wasn't satisfied with the result.
I have a few S/H-series cameras in parts condition. The S1/H1 has curtains that are practically identical in pattern, with only the curtain rollers being different. The S2/H2 (not the S2 Super) are probably exactly identical, but I don't have one on hand to say for sure. In any case, I took the curtains from an H1 that was already missing many other parts.
Being that the curtain rollers in the H1 are different to the AP, I then carefully transferred the H1 curtains to the curtain rollers in the AP.
Two points to note:
- The AP uses the curtain bar of the opening curtain to trigger the flash - thus, ~5mm of bar from each end is sanded to bare brass to accommodate this. The later cameras use a gear to trigger the flash.
- The rubberized side of the curtain is oriented opposite as well - the original curtains in the AP had the rubberized side facing the film, where the H1 has it facing the lens. Minor things that don't impact shooting, but perhaps important if one is interested in a camera that is exactly as it was originally issued.
Honestly, the only real challenging part was getting the curtain, clutch, and wind gears back into the correct orientations. Unfortunately, the camera jammed in the middle of a winding cycle while I was initially testing it before the curtain swap; thus, I was unable to note the correct starting positions of the gears during disassembly. There is no service guide (that I know of) for the original Pentax cameras, so one must make inferences from the guides available for the later cameras to get everything into the proper position. Very logical once you figure it out, but a bit of trial and error to get there.
Probably more than you wanted to know, but it's fun to share anyways.