Pentax MX - mechanical shock releases mirror

[dirbel]

I have a Pentax MX that is basically working, but there is one thing that doesn't seem right:
When I hit the bottom of the camera on the winding side with the palm of my hand, the mirror releases. The shutter stays cocked and can be released normally afterwards. I first noticed this when I got the camera out of my bag and the mirror was up. The slap with the hand is a reliable way to reproduce the effect.

I have tried to adjust the tripping point of the shutter, but no luck there. The service manual does not have much information about the mirror mechanism so I am running out of ideas.

Does anyone here have experience on this?

 

[albada]

I have a Pentax MX that is basically working, but there is one thing that doesn't seem right:
When I hit the bottom of the camera on the winding side with the palm of my hand, the mirror releases. The shutter stays cocked and can be released normally afterwards. I first noticed this when I got the camera out of my bag and the mirror was up. The slap with the hand is a reliable way to reproduce the effect.

I have tried to adjust the tripping point of the shutter, but no luck there. The service manual does not have much information about the mirror mechanism so I am running out of ideas.

Does anyone here have experience on this?

Yes, this happens with both of my Pentax MX cameras (with no lens attached). I tried this a few minutes ago. On both of them, a hard hit with my palm caused their mirrors to flip up.
I suspect this is normal behavior. The g-force of the slap probably causes a lever to move, releasing the mirror.

Mark

 

[LimeyKeith]

There is also the 'MX Flick' method of causing the mirror to flip up without releasing the shutter. Essentially it means just lightly 'flicking' the top of the shutter release button to allow the mirror to flip up. It takes a little practice but it works on my recently serviced MX's. Apparently it is due to the manufacturing tolerances built-in to the mechanism - if this tolerance is biased more one way than the other, then the slight 'jolt' causes the mirror to be released. Obviously it won't work on all MX's.

 

[dirbel]

Hi Mark, thanks for checking this. Seems I can stop searching for a fault - it's by design.
Keith, I had found descriptions of this 'MX Flick' and had adjusted the release so that the release of the mirror happens as late as possible.

Thanks for the quick replies.

Have a nice sunday,

Dirk