Mirror up shutter sticking in 50mm and it was CLA'd a month ago past my 90 day limit

[smcclarin]

I recently CLA's a 50mm Mamiya Sekor Lens at Forsters in SLC, for a sticking Mirror up shutter,
and it appears to be comming back, on my most recent outing yesterday I noticed about 40% of the time the mirror stayed up in my instant prints = overexposing - It took a little while to figure out checking my meter to see if it was at fault, then removing the RB Film back and looking as the mirror went up and the shutter stayed open, only happens about 1/5 times but it is seriously frustrating if I want to do Mirror Up strictly with longer than 1/8 second shutter speeds, I had to finish my shoot without MU hoping for the best with the tripod attached. It was really frustrating and hard to enjoy where I was and what I was doing.
Shoud i work out the MU function more often? or does this lens need another CLA? 120.00 is expensive if I have to CLA once a month, mabey I need a new user lens. Does anyone have a 50mm they no longer want?

 

[paul ron]

Take it back even though the 90 days is up, that souldn't happen. Sounds like the MU lever is bent or worn.

 

[John Koehrer]

It's not the body, if the shutter is staying open. The shutter has to close for the cycle to complete.

 

[paul ron]

Question... does this happen with all the lenses you own or jsut this one?

The lens sounds faulty. If it was CLAed then the shutter shouldn't stick open in any mode and should preform for a good few years, not a month.

In MU the mirror flys up when the body is fired, the lens closeses at this point till you fire the cable. Inside the lens, a lever responsable for MU catches the actuating ring as it comes around, closes the shutter blades till the cable is fired then it lets the ring complete it's rotation to fire the shutter at the speed selected. If this isn't happening, the shutter needs to be serviced or wasn't serviced properly. The probem you describe as shutter staying open in that part of it's cycle is a problem with a small srping that slips it's post or is borken.

Send it back!

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[smcclarin]

Forsters did more than right, turns out it got too hot at the wave and vaporized the grease off the shutter. they re greased, re CLA'd at no cost, which I greatly appreciate, I take better care of my lenses now. The 50mm C is working great these days. thanks for your support and recommendations.

 

[paul ron]

Glad to hear they did the right thing n re-CLAed it for ya.

I'm not sure I understand.. you say it got too hot n vaporized the grease? How hot was it?

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[smcclarin]

I was told that the shutter grease had vaporized, was not where it was placed when it was CLA'd, and that it can only be one reason...left in sun or heat for longer than 30 minutes. I do compose some scenes with the sun in frame, perhaps since the shutter is between lenses at focal point...I am heating up the shutter blades...have taken care to compose sunset shots quickly and cap the lens before I am ready to shoot...50mm lens still works like a champ so far!!