M3 shutter speed adjustment

[cnphoto]

So, feeling adventurous, I just tightened the curtain tension ever so slightly in small increments on my M3 to resolve a past issue with the first curtain hanging back on slower speeds (and entering the left of the frame a little on slow speed exposures). The curtain no longer hangs back and everything looks good.

I have also previously noted that the 1 second speed is closer to 1.5 seconds, more or less. If I where to get a shutter speed tester (or build a shutter speed test unit) how would I adjust the shutterspeeds? Does anyone have any online resources detailing how this is done on an M series camera?

[colyn]

If the shutter speeds are off the camera needs a CLA. Tensioning the curtains can over stress the drum springs causing failure.

[cnphoto]

correct, but a minor adjustment (as i have done) should be fine. 1/4 turn at most.

[colyn]

Originally Posted by cnphoto

correct, but a minor adjustment (as i have done) should be fine. 1/4 turn at most.

1/4 turn is a lot since fine tuning to set curtain speed (not shutter speed) takes less than 1/8 turn increments.

[mooge]

you'd probably want to crack it open or send it in if it bugs you. sounds like you could use a re-lube.

I don't think a 1/4 turn can be harmful, anyways.

[cnphoto]

it was, in reality, less than a 1/4 turn. hence: 1/4 turn at most

yes, i'll probably send it in for a CLA eventually. the shutter curtain encroaching into the image frame was more annoying than the shutterspeeds being off a little, if there was a how-to or simple way to lube/adjust shutterspeeds (even just the slow speeds, to get 1sec closer to tolerance) i would possibly do it myself, then again send it in for a CLA when I can be bothered / it really annoys me.

otherwise, it is as quiet as my M4-P and has a smoother advance, so there are no other issues with it

[colyn]

Originally Posted by dragunov

I don't think a 1/4 turn can be harmful, anyways.

Leica shutters work on little drum spring tension unlike Japanese SLR's which require heavy tension. For example when servicing a Leica during rebuild the curtains are pre-tensioned. The closing curtain only needs 1 3/4 total turns to work properly. 6 turns total is average for the opening curtain tension. If the opening curtain needs more than 7 turns total something is wrong.. These springs are not made to withstand more tension without possibly breaking. Remember when advancing the shutter you add tension to them..

Therefore a 1/4 turn can cause failure of the shutter springs..in part because the reason the shutter is not working properly is dried lube and dirt buildup..not loosening of the spring tension...

[jn053]

Originally Posted by colyn

Leica shutters work on little drum spring t...

Bait, bullpoo, or both. Who told you this ? You're roughly
correct about the base tension, assuming your idea of
the shutter's rest position is written in stone. To get past
the guesstimate, we have curtain velocities and shutter
speed testers. But breakage ? Surely you have more
respect for German engineering.

And your statement about Japanese SLRs is off. Spotmatics
came out of the factory with no more than 2 1/2, 1 1/2 turns.
Roughly speaking, of course.

If the camera has never been serviced _properly_, a CLA
is in order. Period. Just do it. No more worries.

[colyn]

Originally Posted by jn053

Who told you this ?

I've rebuilt roughly over 200 Leicas in my lifetime so the info is from experience and Leica factory overhaul/repair manuals.

Originally Posted by jn053

You're roughly
correct about the base tension, assuming your idea of
the shutter's rest position is written in stone.

Leica shutter have very little room for error here. A little too far in and the lathe starts to overlap the opening curtain drum. Too far out the same situation but the closing curtain lathe overlaps the main shutter drum..

Originally Posted by jn053

To get past
the guesstimate, we have curtain velocities and shutter
speed testers. But breakage ? Surely you have more
respect for German engineering.

I agree when servicing cameras whether they be Leicas or other brands you need proper tools which I have. for the Leica that is...shutter velocity can be set on the Leica with just a shutter tester..

German engineering is no different than others..When you over-tension these springs they will overlap and stretch. In time they break but they can last a lifetime if properly adjusted to prevent over-tensioning.

Originally Posted by jn053

And your statement about Japanese SLRs is off. Spotmatics
came out of the factory with no more than 2 1/2, 1 1/2 turns.
Roughly speaking, of course.

Spotmatic shutters were patterned after Leica shutters. Other Japanese cameras used higher velocity shutters..

Originally Posted by jn053

If the camera has never been serviced _properly_, a CLA
is in order. Period. Just do it. No more worries.

I couldn't agree more. This is why I cautioned the OP about doing self adjustments which can cause damage.