Pentax Auto 110- aperture diaphragm sticks closed with mirror up

ProgramPlus

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This seems like a good site for camera repair so I thought I'd ask here.
Got an Auto 110 on Craigslist. The aperture diaphragm is closed and mirror is up. Obviously with the mirror stuck up, everything is dark through the viewfinder. Every once in a a while you can smack the bottom of the camera on the heel of your hand and the aperture diaphragm opens up and the mirror flips up. Winding the camera (twice) and firing the shutter, it sticks again. Any theories as to what is causing this and if it's fixable? Batteries are good.

Checking the Pentax sites, when others asked about even more fixable problems (like the slipping film advance) the common response is "they're cheap, buy another." They're less cheap than they used to be and I'm a tinkerer so I'd like to take a crack if there's a chance to salvage this one. Otherwise it'll be used for parts I guess.

Thanks in advance.
 

Ces1um

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I've also found a lot of sites that say if your batteries are weak/dead that the mirror will get stuck. Maybe it's that?
 
OP
OP

ProgramPlus

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Thanks for the replies. That's a great link. It's great that the the gentleman who owns the site chooses to keep it going so long after these cameras haves ceased being particularly relevant. There's a potential fix he lists on that site for the slipping film advance that it one of the achilles heels of these cameras. I got a broken Auto 110 for cheap because of that problem. For now I choose to still use the camera with the auto winder, but when the winder conks out, I'll try to fix that one for real.

Pretty sure it's not the batteries but I"ll check again. The batteries are new and when I pull them out and put them in another Auto 110, they are fine.

On the upside, I got a flash with the sticking mirror 110 that wasn't initially working, got it cleaned up and working now, so it wasn't a complete bust.
 
OP
OP

ProgramPlus

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Update,
I pulled the bottom and top plate off the camera. Under the camera, beneath the lens mount, there is a small vertically oriented sprocket. Tinkering around I found to slightly turning this sprocket would release the stuck aperture diaphragm and release the mirror. Cocking the camera and pressing the shutter release, it jambs again. Releasing the aperture diaphragm and shutter again and doing it several times, it finally stopped sticking. Now it works fine. I guess it just got a little sticky from lack of use. Seems to work fine now. Meter seems to adjust the shutter speed appropriately so I think she's good to go.
 

Huss

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Update...
I noticed that when the camera jams, the exposure LED glows orange, no matter how bright the light source is. Never jams when it is green.
I bought a can of CRC QD Electronic Cleaner for my local Ace Hardware, and without disassembling the camera, gently sprayed it into the shutter speed button and space around it and the top plate, then worked the shutter button so it fully penetrated. The cleaner is highly volatile and evaporated rapidly leaving no residue.
I did the same for the manual sync switch on the left side.

The camera has since stopped locking up.
 

Cholentpot

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I'll give this a try. I've had plastics that have gone brittle when exposed to some electronics cleaners. I think it comes out of the can super cold.
 
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