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  1. #1
    Steve Smith's Avatar
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    Pentax S1a - Shutter Problem

    I have been given a Pentax S1a. Initially it had a problem with the shutter speeds slower than 1/30 where the second curtain would not close. A quick look under the bottom plate found the problem and after a slight re-bending of a piece which holds the second curtain open, the shutter now opens and closes on all speeds.

    The problem is that the speeds below 1/30 are all very fast and seem to be the same.

    I have not checked 1/30 and faster yet but they seem to get progressively faster when viewing a light source through the open back.

    My question is this: Do the speeds below 1/30 use a different mechanism which somehow is not engaging now?

    If that is the case and speeds from 1/30 to 1/500 (and perhaps the 'hidden' 1/1000) are o.k. then I will not try to repair the slower speeds and just use it from 1/30 upwards. I almost always use 1/125 hand held anyway.

    In all other respects, this camera is in excellent condition and it would be a shame not to use it.



    Steve.

  2. #2

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    Steve,
    Yes, the slower speeds use an escapement mechanism to control the timing.
    If the 2nd curtain wasn't closing, the curtain travel times most likely needed to be adjusted. This is done with the worm gears visible beneath the bottom plate and probably very near the lever you bent.
    Heavily sedated for your protection.

  3. #3
    Steve Smith's Avatar
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    Thanks for the info.

    Initially on speeds slower than 1/30, the first curtain would open but the second curtain wouldn't close. I noticed that a small pressure on the little lever I mentioned released the second curtain so I bent it down very slightly.

    I will have another look at it but if it is working from 1/30 and faster I might just leave it alone. I can use the oscilloscope and a photo-diode at work tomorrow to check the shutter speeds.



    Steve.

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    Hi Steve,
    I acquired a Spotmatic with no speeds slower than 1/30th for no other reason than it was very cheap!. As John says, it's almost certainly the slow speed escapement. I dismantled the Spotmatic, which necessitated removing the mirror box, freed the escapement mechanism with a few drops of lighter fluid to dissolve the ancient, gungey lubricant and then once the mechanism was moving freely re-lubricated it. Not a difficult job, just one requiring a bit of patience and a set of jeweller's scredrivers. A good job for a cold winter's evening! If you do decide to give it a go I can send you some disassembly info if needed.

    Steve

  5. #5
    Steve Smith's Avatar
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    Thanks.

    I have tested the speeds fom 1/30 upwards and they seem to be o.k. so I will probably leave it alone.

    My curious side is interested though. If you have any info or pictures from your repair and it's not too much trouble, I would be interested in seeing it.



    Steve.

  6. #6
    Ian Grant's Avatar
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    Back in the UK I have an older Pentax that needs repair, I was given it broken. The shutter blinds need re-attatching, any info on how you disassembled your S1a would be useful, mine's an S.

    Ian

  7. #7
    Steve Smith's Avatar
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    I have only taken the bottom plate off of mine so far (just four screew on the base). I don't really want to go any further as it is in a useable condition right now. Sometimes my repairs turn cameras into a pile of spare parts!

    Steve Roberts' Spotmatic repair may provide you with more useful information though.



    Steve.

  8. #8
    Ian Grant's Avatar
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    Too many Steve's I meant to ask Steve Roberts

    Ian

  9. #9
    Steve Smith's Avatar
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    Thought so. Except you said S1a!!

    This could be useful: http://www.lensinc.net/pentaxrepair.html But as a last resort as it involves spending money. $5.95 !!!



    Steve.

  10. #10

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    Steve and Ian,
    There are two Spotmatic repair manuals downloadable for nowt at http://www.robertstech.com/manuals.htm
    One is the manufacturer's and the other produced by National Camera. The Spotmatics and S1a/S's have some parts/assemblies that are remarkably similar and some that are quite different (such as the exposure counters) but a look at the Spotmatic info should give you the general idea. Watch out for anti-clockwise threads around the exposure counter - these seem to vary so if something won't come undone easily have a close look at any exposed part of the thread. Ian - re-attaching the shutter blinds is something I've only read about (in Tomosy vol 1). Personally, I'd think long and hard before tackling that!

    Steve

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