Olympus OM2 shutter speed problems in Auto mode

I'm having some issues with metering in auto mode on an OM-2. The problem is the actual shutter speed during exposure is much longer than the shutter speed indicated by the meter. For example the indicated speed might be 1/125 but the actual shutter fires at around 1/15th or slower (judging by ear).

 

Here's what I know so far:

-Viewfinder metering is consistent between auto and manual modes.

-Viewfinder metering is consistent with my DSLR at the same ISO/Aperture, therefore the issue must lie with the actual shutter speed being selected by the camera.

-My testing was done with brand new silver oxide cells fitted and film loaded.

-In manual mode, shutter speeds sound about right (by my not-so calibrated ears)

-I replaced the mirror stop foam as it was a bit sticky.

 

My initial conclusion is that there is a problem with the two SBC blue light sensors in the bottom of the mirror-box, which I guess must be reading incorrectly and causing the slow shutter speeds? I checked if they were dirty, one had a little dust but gently cleaning it made no difference.

 

I did also notice that the Manual/Off/Auto switch on top of the camera is a bit tempremental, and sometimes requires a wiggle to make contact at the chosen setting. Could this be the cause of the auto-mode issue (doesn't seem likely though)?

 

So my question is, what is the next step in my investigation? I understand there is variable resistor under the mirror box which controls the SBC metering circuit, would it simply be a case of adjusting this to correct the speeds, and is this easily accessible under the mirror box base? Otherwise, are there any other common faults here that I can check for?

 

For info, I'm fairly competent at basic camera repairs and have tackled some pretty challenging jobs on other cameras. I say this because I'm keen to try and get this repaired myself, however I will submit to a professional repair if it's out of my reach.

 

Any advice is greatly appreciated.

You may not have a problem at all. The OM2 has two separate metering systems. One measures through the prism and that is what you see in the finder. The second system measures the reflectance of the film. It all starts with an approximate shutter speed from the viewfinder , than when the mirror goes up,the lens diafragm closes down, the shutter opens and is then controlled by the sensors that measure reflectance. If there is no film in the camera, it will measure from the pressure plate which is black and so gives a much longer shutter time. It is a wonderful system that really works well, as long as you have a film in your camera.

The OM10 also works like that. Never use the automatic setting without a film in the camera. Of course, if you had a film in the camera, you might think of buying another (working) one.

That's my understanding too, and the problem is that I did have a film in the camera at the time of testing!

I'm sorry my answer was not true. It was a bit too late at night for me. What I described was the way the OM10 works, not the OM 2. The OM 2 measures the incoming light from the first shutter curtain and only with longer shutter times uses the reflectivity of the film. A weird thought of mine: what happens when the real F value of the lens is not transferred to the camera? The lens then seems to transmit more light than it really does. It would give the same effect that you now have. When you look through the viewfinder and change the F value of the lens, does the shutter time display change? I mean, it doesn't have to be the electronics of the measuring cells.

Good luck with it. And don't forget, thanks to digital, secondhand OM2's can be quite affordable.

I've checked what you describe, and yes when looking through the viewfinder, changing the aperture on the lens does affect the light meter and does change the shutter speed. So for example, at f1.8 the meter indicates a shutter speed of 1/125 but actually fires at around 1/15th. Then when the aperture is changed to f8, the meter indicates 1/30th but the shutter fires at around 1 second!

To reiterate, in Auto and Off mode, the OM-2 judges the exposure by the light reflecting off the film into the main circuit's cells -- the needle in the finder is an indicator only, and does not actually control the exposure in any way.

 

But what you describe is different. In all likelihood, the contacts of the mode switch (the switch on the main circuit below the mirror that sets it for Auto or Manual exposure control) are not making a good connection. This can cause erratic exposures in either or all modes, by the way. This is something that should be included in any routine repair of an OM-2, as well as cleaning the trigger switch contacts (by the armature), the main- and sub-switch on the side of the mirror box, the fixed resistor board and contacts that control the manual speeds, and the ASA board and contacts around the meter up top. Most of this work requires rather through disassembly, however.