Pentax H3v Shutter Adjustment

BAC1967 · Apr 24, 2016

I recently purchased a bunch of M42 lenses with a Pentax Spotmatic and an H3v. The H3v has a problem where there is a gap in the shutter curtain when it is being cocked. I can see light coming in from under the mirror. I could use the camera if I remember to put the lens cap on before cocking the shutter but that's not going to happen. I can move the left curtain forward to close the gap by gently pushing on it so there is clearance for it to move into the correct position. Looking at the attached photo below it looks like the curtains may have sustained some damage but I don't think it's as bad as it looks.

I believe there are two screws under the base plate that are used to adjust the spring tension of the shutter, one for each shutter. I don't want to mess with that if there is the possibility of causing more problems while not fixing the gap.

I believe this camera is very similar to the Pentax S, S1, S2 and SV models. It's also quite similar to the Spotmatic, but it doesn't have a light meter. It's not worth the cost to send it out for repair. Any help will be appreciated.

Pentax H3v by Bryan Chernick, on Flickr

David Lyga · May 4, 2016

I do not think that this is a matter of adjustment (which is done simply enough under the camera: there are two ratchet screws close together), as such adjustment simply makes either the first or second curtain more or less tensed. Here, there is a problem with the two curtains not meeting closely enough, which leads me to believe that one curtain's two apron strings, holding its curtain to its round post, is too short, or glued too far around that post so that its reach does not conform with complete and necessary overlap.

That is rather tricky to correct, as it means you must remove the four front screws holding the mount area, un-glue those specific apron strings, then re-glue at the proper point. If you do remove this mount be especially careful to not let those four tiny, light brass spacers under the mount get into the body.)

That said, there MIGHT be a simple tensioning of a curtain to make. Cock the shutter half way so that the slit is as you show in the picture. Then gently move each curtain separately 'BACK' to the neutral position to feel if one of the curtains is not sufficiently tensioned. If the springiness is too weak, that curtain's ratchet screw needs to be slightly tightened.

By the way, I consider these pre-Spotmatic versions of Pentax to be the most aesthetic of all SLRs. - David Lyga

BAC1967 · May 4, 2016

David Lyga said:
I do not think that this is a matter of adjustment (which is done simply enough under the camera: there are two ratchet screws close together), as such adjustment simply makes either the first or second curtain more or less tensed. Here, there is a problem with the two curtains not meeting closely enough, which leads me to believe that one curtain's two apron strings, holding its curtain to its round post, is too short, or glued too far around that post so that its reach does not conform with complete and necessary overlap.

That is rather tricky to correct, as it means you must remove the four front screws holding the mount area, un-glue those specific apron strings, then re-glue at the proper point. If you do remove this mount be especially careful to not let those four tiny, light brass spacers under the mount get into the body.)

That said, there MIGHT be a simple tensioning of a curtain to make. Cock the shutter half way so that the slit is as you show in the picture. Then gently move each curtain separately 'BACK' to the neutral position to feel if one of the curtains is not sufficiently tensioned. If the springiness is too weak, that curtain's ratchet screw needs to be slightly tightened.

By the way, I consider these pre-Spotmatic versions of Pentax to be the most aesthetic of all SLRs. - David Lyga

Thanks for the response David. That's what I was afraid the problem would be. That kind of repair is beyond anything I've done before but I may give it a shot if I feel ambitious. I suspect it's the curtain to the left in the photo above, it seems kind of loose and it looks like it's the one that's the most out of alignment.

David Lyga · May 4, 2016

If I could hold the camera in my hand, I might be more enlightening as I have worked on many, But modifying the apron strings is tricky.

I believe that the left curtain is the FIRST curtain (first to allow film to be exposed). If I remember correctly, that ratchet screw is the one closest to the REAR of the camera, (under that bottom plate). It MIGHT simply be a matter of turning that screw about half a turn with a screwdriver (or more if not resolved). If that works you will not have to remove the mount area. (Done in five minutes.) - David Lyga

BAC1967 · May 4, 2016

David Lyga said:
If I could hold the camera in my hand, I might be more enlightening as I have worked on many, But modifying the apron strings is tricky.

I believe that the left curtain is the FIRST curtain (first to allow film to be exposed). If I remember correctly, that ratchet screw is the one closest to the REAR of the camera, (under that bottom plate). It MIGHT simply be a matter of turning that screw about half a turn with a screwdriver (or more if not resolved). If that works you will not have to remove the mount area. (Done in five minutes.) - David Lyga

Thanks, I'll try that first.

shutterfinger · May 4, 2016

I would lock the shutter open on B and check the curtain rails/path for obstructions or dried lubricant that may have migrated. It may be dried/old lubricant on the curtain drums pivot shafts also. I would adjust spring tension as a final resort if all else is good.

John Koehrer · May 4, 2016

The camera does need a bit of new oil.
The gap is because the tension on the closing curtain needs to be tweaked a bit. Actually both probably need to
be adjusted to balance them. The Spotmatics were 12.5ms A lot of amateurs will back all the tension off both curtains and then wind them
the same number of turns as a starting point, then make minor tweaks. I't a WHOLE lot easier with a shutter tester.
A bit of cleaning, lubricating and adjusting should solve the whole thing.
Without the cleaning part it'll just creep out of adjustment again.

David Lyga · May 6, 2016

The MOST important thing to do is to gently move each curtain with a tiny screwdriver to see if it is in any way encumbered. If it is loose, or easily moved, there is no problem. Be CAUTIOUS about adding lubricant: when new, there is NO lubricant for those curtains. - David Lyga

Pentax H3v Shutter Adjustment

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