Olympus OM-2 shorts battery when film advance lever is at certain positions

[nickajeglin]

Hello,

History: I have an OM-2 that I'm working on. Originally it had issues with unpredictable mirror lockups and occasional issues with the asa reading causing problems in auto. I replaced the back foam and removed the prism foam. Then I did some light contact cleaning of the on/off switch and asa contact/resistor board. That resolved the issue in manual. I was still seeing some problems in auto, so I opened it back up to adjust the A contacts and replace the insulating washer over the asa cam setup. That worked perfectly, and now I can use both auto and manual as expected at all asa's.

But... I have created another problem. Now, moving the film advance lever will short out the battery (obviously also causing lockup). Specifically, whenever the lever is "pre-advanced" just to the point where it starts to engage, the battery will short. So if I hold the battery test lever, the light will be steadily on, but will go dark right as I start to feel resistance in the lever. A multimeter across the battery terminals will see continuity at that time.

I'm not sure where to start hunting for shorts. I've checked all the short locations under the top cover that are listed in the repair manual and I've added scotch tape to the cover as instructed just to be safe. At this point the manual seems to point me in the direction of the main switch plate and the M contacts, but I'd like to avoid removing the front casting if I can.

Can anyone point me in the right direction? Since the failure is so specific I was hoping that someone knowledgeable could identify the problem really easily, whereas I'll have to start checking every possibility by exhaustion.

 

[nickajeglin]

For anyone else who finds this, I was able to fix it. I had been messing around with the battery box during my earlier repairs, and I apparently managed to drop the plastic insulator that goes in between the winding shaft and the tube under the box. Without the insulator, the winding shaft is loose on the bottom and will tilt over as soon as it meets any resistance, shorting it to the tube under the battery box.

I unsoldered the battery box wire, pulled it up and found the insulator stuck to the side of the shaft by grease (thank god). I reassembled correctly, and now I'm back in business. The part is CE051200, and can be found on fig. 1/8 of the OM-2 repair manual. You can also get a much better view on page 143.

Next problem: perforation position is off by a couple mm. I'm off to the OM-1 manual for that I guess.

 

[Flighter]

Thanks for the follow up, I've stored it away for future reference.