Pentax 6×7 Intermittent Shutter & Mirror Lockup Problem Solved
I had almost given up on fixing the shutter issue on my Pentax 6×7 and was ready to resign myself to sending it off to a specialist repairer. The problem was most annoying because it was intermittent. Every now and then, for no apparent reason and with no discernable pattern, pressing the shutter release would cause the mirror to lock up and not return until I removed the battery. Pressing the mirror return button on the front had no effect either. The only clue was that it seemed to occur more often on certain shutter speeds.
While researching the problem online I found a few references to the contacts under the shutter speed dial getting dirty and causing similar symptoms so I thought it would be worth a try cleaning them before incurring a potentially large repair bill. Fortunately it turned out to be a very easy task.
To gain access to the shutter speed contacts I had to first loosen the three small set screws on the selector dial. Do not remove them, just loosen them enough so you can lift off the dial. Under the dial is also a clear plastic washer to prevent dust entering the opening around the speed shaft; I removed this too.
Next I removed the three cross head screws holding the cover to the body. There is one on rear of the cover, next to the battery check button, another in the same position on the front of the cover, and a final screw on the edge of the body.
I had to remove the viewfinder prism to lift off the cover, and then I had access to the switch contacts. The contacts looked very dull and had some dust on them, none of which is good! I used a Q-Tip dampened with some isopropyl alcohol (rubbing alcohol) to clean the contacts, and then another dry one to clean up any excess from around the switch.
Once I had the contacts looking nice and shiny again I tried firing the shutter on all speeds a few times and then put it all back together. Since performing this cleaning, I have dry fired the camera close to 100 times, and successfully shot a test roll, all without any mirror lockup issues, and I’m fairly confident I’ve fixed the problem.
Hopefully this may help anyone else who is having the same trouble with their Pentax 6×7.