Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-22-2023, 03:41 PM   #1
New Member




Join Date: May 2023
Posts: 2
MX mirror rises when film advance lever is pulled - Is it a DOF preview issue?

Hi everyone,

I've had increasing issues with my much loved MX lately and I can't afford a CLA.

I've been trying my hand at some basic repairs, so far cleaning the mechanical areas under the bottom panel with alcohol and a fine brush. I know the light seals and dampers need replacing on the mirror, but I think there may be a more significant reason the mirror locks up.

When using the camera, cocking the shutter brings the mirror up, meaning you can't see anything while taking a photo. It renders the camera useless. Weirdly, switching this small lever on the left hand side of the mirror -down- before cocking prevents this from happening and the camera will fire as normal for one shot, then back to this odd behaviour. The DOF preview works normally if a lens is attached but only if this lever trick is done before attaching a lens.


I've attached a video I put on YouTube to best explain what I mean!

I wondered if anyone might know anything about this issue? I have searched articles about similar issues but none linked to this behaviour with the DOF lever.

thanks all!



05-23-2023, 12:05 AM   #2
Moderator
Loyal Site Supporter
Loyal Site Supporter
pschlute's Avatar

Join Date: Mar 2007
Location: Surrey, UK
Photos: Gallery
Posts: 8,113
QuoteOriginally posted by fbrannan Quote
I wondered if anyone might know anything about this issue?
I will move this thread to the Film SLR forum where hopefully you are more likely to get an answer from our film camera experts.
05-23-2023, 08:22 AM - 1 Like   #3
Site Supporter
Site Supporter




Join Date: Oct 2022
Location: Midwest
Posts: 129


This is the bottom of the mirror box for the Pentax MX. The red arrow is pointing to a post that interacts with the winding mechanism. As you wind the camera, a long arm pushes this post to the left (front of camera). You should be able to see this happen with the bottom plate of the camera removed. If the camera is operating correctly, only the left end of the spring (green arrow) should move. The right end (blue arrow) should stay in place, loading the spring so it can quickly flip up the mirror. On your camera both are moving, so the mirror moves up as you wind the camera. To see why, we need to look at the side of the mirror box.



The red and blue arrows are pointing to the same things, just seen from a different point of view. The purple arrow is pointing at the little lever that sticks out into the lens mount. That's what you wiggled to get it working but normally it's what stops down the aperture in the lens . The pink arrow is pointing to the lever that flips up the mirror. The yellow arrow is pointing to a latch that is supposed to hold the mirror up mechanism in place as you wind the camera. I think this is where the problem is. There is a small bias or return spring which is supposed to return the latch to its proper position after the shutter is pressed (pressing the shutter moves the latch allowing the mirror to flip up before firing the shutter). The latch on your camera is probably too gunked up and the spring is not strong enough to return it to the home position. Messing with the stop down lever (purple arrow) probably provides just enough extra force to get it to return, at least for one cycle.

I hesitate to recommend this, but you might be able to free up that latch pivot by carefully applying some solvent (Isopropyl alcohol) through the gap around the stop down lever. Then run it through a bunch of cycles to work it in. But even if you get it firing consistently, it's likely just a temporary solution. The proper fix is a disassembly of the camera so you can clean away all the old gunk. Look up Erik Hendrickson at pentaxs.com. His price for a standard CLA are pretty reasonable.

Last edited by vandergus; 05-23-2023 at 10:41 AM.
05-26-2023, 02:56 PM   #4
New Member




Join Date: May 2023
Posts: 2
Original Poster
QuoteOriginally posted by vandergus Quote

This is the bottom of the mirror box for the Pentax MX. The red arrow is pointing to a post that interacts with the winding mechanism. As you wind the camera, a long arm pushes this post to the left (front of camera). You should be able to see this happen with the bottom plate of the camera removed. If the camera is operating correctly, only the left end of the spring (green arrow) should move. The right end (blue arrow) should stay in place, loading the spring so it can quickly flip up the mirror. On your camera both are moving, so the mirror moves up as you wind the camera. To see why, we need to look at the side of the mirror box.



The red and blue arrows are pointing to the same things, just seen from a different point of view. The purple arrow is pointing at the little lever that sticks out into the lens mount. That's what you wiggled to get it working but normally it's what stops down the aperture in the lens . The pink arrow is pointing to the lever that flips up the mirror. The yellow arrow is pointing to a latch that is supposed to hold the mirror up mechanism in place as you wind the camera. I think this is where the problem is. There is a small bias or return spring which is supposed to return the latch to its proper position after the shutter is pressed (pressing the shutter moves the latch allowing the mirror to flip up before firing the shutter). The latch on your camera is probably too gunked up and the spring is not strong enough to return it to the home position. Messing with the stop down lever (purple arrow) probably provides just enough extra force to get it to return, at least for one cycle.

I hesitate to recommend this, but you might be able to free up that latch pivot by carefully applying some solvent (Isopropyl alcohol) through the gap around the stop down lever. Then run it through a bunch of cycles to work it in. But even if you get it firing consistently, it's likely just a temporary solution. The proper fix is a disassembly of the camera so you can clean away all the old gunk. Look up Erik Hendrickson at pentaxs.com. His price for a standard CLA are pretty reasonable.
Hi Vandergus,

Sorry for a late reply, been at work all week.
Thank you very much for such a comprehensive and well put answer, you've been a huge help.
I tried applying iso alchohol around the mirror rise lever to try and 'work' it into any buildup there, but I'm afraid it's only improved the situation slightly, to maybe having 9 in 10 advances having the issue. It would seem like a CLA is the only option, as without working on simpler cameras a teardown to access the mirror box seems daunting and there doesn't seem to be any comprehensive guide to the process online, besides the MX repair manual, which seems difficult in itself...
I'd better get saving...

Fin

05-26-2023, 06:59 PM - 1 Like   #5
Site Supporter
Site Supporter




Join Date: Oct 2022
Location: Midwest
Posts: 129
QuoteOriginally posted by fbrannan Quote
Hi Vandergus,

Sorry for a late reply, been at work all week.
Thank you very much for such a comprehensive and well put answer, you've been a huge help.
I tried applying iso alchohol around the mirror rise lever to try and 'work' it into any buildup there, but I'm afraid it's only improved the situation slightly, to maybe having 9 in 10 advances having the issue. It would seem like a CLA is the only option, as without working on simpler cameras a teardown to access the mirror box seems daunting and there doesn't seem to be any comprehensive guide to the process online, besides the MX repair manual, which seems difficult in itself...
I'd better get saving...

Fin
Yeah it's not exactly a simple repair. But if you do feel like taking it on, here's a pretty good tutorial. It's a little easier to follow than the service manual. It will require a spanner wrench and some basic soldering skills, in addition to other standard tools.

Product Details | Pentax MX CLA Tutorial | Pentax | Service Manuals | Learn Camera Repair
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dof, dof preview, film advance lever, hand, lens, lever, mirror, pentax service, preview, repair, service, warranty
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pentax MX's not-so-smooth advance lever Daveee Film SLRs and Compact Film Cameras 15 11-24-2021 12:44 PM
K1000 - film advance lever clicking, film wont budge. hiddenvibe Film SLRs and Compact Film Cameras 6 01-20-2015 04:52 PM
How to make sense of the DOF preview/Optical preview on the on/off dial ? photoleet Pentax K-5 & K-5 II 5 04-17-2012 04:22 AM



All times are GMT -7. The time now is 12:05 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top