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11-10-2010, 01:19 PM   #1
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MX mirror stuck up - is one of you knowing the remedy?

I bought me a deadly cheep MX with a little bump on the top of the prism house (nr. 9340468), coupled with an M 50/1.7 lens. Never had an MX before, but boy, I like it! The feel, the size, the metalic colour, the sound of the mirror and the winder, and above all the viewfinder .

I had no batteries in it today, but I shot a whole role of Iford B&W film just to see whether the camera has issues, like light leaking etc. Of course I can't say anything about that right now, because I don't develop film myself, but the 20 minutes try revealed another problem of the camera: in about 1/3 of the cases the stayed stuck up. Unmounting the lens made it possible to force the mirror back down, but soon as I let it slip, the lens made it's move right up to get stuck to the prism. For this first roll of film no problem, but it's a waste of film - and more important: of photo opportunities! - to leave it this way.

So: anyone an idea what causes the problem, and how to resolve it??? Thanks in advance!


Last edited by Rense; 11-10-2010 at 01:30 PM.
11-10-2010, 01:55 PM   #2
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The mirror got stuck during the longer shutter cycles, right? Like 1/2 sec or 1/4 second. But does not get stuck in the up position when you use a faster shutter speed, like 1/500 or 1/250?

Likely a case of the mirror timer in the bottom of the camera is gummed up with goo.

Time for a CLA.
11-10-2010, 01:58 PM   #3
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Moe, thank you! Shutter speed was 1/125"....
11-10-2010, 02:05 PM   #4
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Moe, I did a little test, firing the shutter at several speeds 10 times for every speed:

1/1000: 10 ok, 0 stuck
1/250: 10 ok, 0 stuck
1/60: 9 ok, 1 stuck
1/4: 2 ok, 8 stuck

So it seems you're right! Is this a problem I can solve myself, or do I have to send it to an expert?

11-10-2010, 02:15 PM   #5
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You need to replace the mirror bumper. With a camera that age, I think you need to replace the light seals also.

Read this

Read this too

Contact Jon_Goodman@yahoo.com to buy materials (I think he is "interslice" on FleaBay).
11-10-2010, 03:37 PM   #6
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QuoteQuote:
Moe, I did a little test, firing the shutter at several speeds 10 times for every speed:

1/1000: 10 ok, 0 stuck
1/250: 10 ok, 0 stuck
1/60: 9 ok, 1 stuck
1/4: 2 ok, 8 stuck

So it seems you're right! Is this a problem I can solve myself, or do I have to send it to an expert?
It does not sound like you have a sticky mirror bumper, or a sticky shutter. Instead, the mirror timer mechanism in the bottom of the camera is gummed up with goo, most likely from decaying foam seals.

My advice is send it to an expert for CLA. It sounds like your MX needs a very good internal cleaning and re-lubrication.

There is a very good expert here in the USA, named Eric, mentioned all over this discussion board. I have sent 3 Pentax film cameras to Eric so far, including my MX, and I have been very pleased with the cameras when they returned to me. I don't know who your European equivalent is.

Last edited by Moe49; 11-11-2010 at 06:21 AM.
11-10-2010, 06:28 PM   #7
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Eric's prices are very reasonable, and his work excellent.

I bought a nigh-busted MX, got it working, and replaced all the seals. Then, knowing it was usable, and a really nice camera, but with a focusing accuracy problem (mirror tilt adjustment), I sent it to Eric for a clean/lube/adjust, and it came back working perfectly.
11-10-2010, 10:31 PM   #8
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QuoteOriginally posted by Rense Quote
Moe, I did a little test, firing the shutter at several speeds 10 times for every speed:

1/1000: 10 ok, 0 stuck
1/250: 10 ok, 0 stuck
1/60: 9 ok, 1 stuck
1/4: 2 ok, 8 stuck

So it seems you're right! Is this a problem I can solve myself, or do I have to send it to an expert?

You will probably need a CLA (clean-lube-adjust): it is a "sticky" shutter. Usually the slower speeds are affected first.

The camera probably hasn't been serviced since new.

After that, it will probably go without any problems for another 40 years.

11-12-2010, 04:37 AM   #9
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Thank you all! In the short time I have this little gem, I fell completely in love with it, so I think I will have it repaired. Have some problems with my 6x7 too, so I can send them together.....
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