I have a collection of older film cameras I randomly pic up for an outing. Several of them used the mercury batteries of the day. For a while, I had just been using the air hearing aid batteries. These worked OK but do self drain/wear out with time once the seal is removed. They also seem more prone to leaking if you forget about them. There are adapter$ but I never bought them. Years ago I had modified a couple Olympus cameras I have so thought now it was the F1s turn.
The F1 was actually quite easy to do, remove the battery cover and the bottom plate comes off, remove 3 small screws and a sub plate comes off and theres the the only wire you care about. I removed the whole battery holder assembly but the job could also be done with everything in place.
I used a BAT83 Diode to do the voltage drop.
Unsolder the red wire from the battery tab and solder the anode ( non band end ) to the red wire, and solder the cathode ( band end ) to the battery tab. That's pretty much it. It all tucks inside neatly.
A word of caution, the red wire does not have much slack, don't want it to disappear into the body. It seems you also can not pull on it much. When I first finished the mod the meter was way off. When I investigated, I was seeing full battery voltage at the meter. In the end, I added some wire to give some slack and then it worked fine. My service manual does not show how this is wired inside, so I'm not sure what the cause of the issue was, only that loosening things up made it work.
When all was done and working, the F1s meter seems to be with 1/3 stop of an FE2 I compared it to.
I will get out and put a roll of film through it but I expect it will be fine. Now I just use Silver batteries and an O-ring.
The F1 was actually quite easy to do, remove the battery cover and the bottom plate comes off, remove 3 small screws and a sub plate comes off and theres the the only wire you care about. I removed the whole battery holder assembly but the job could also be done with everything in place.
I used a BAT83 Diode to do the voltage drop.
Unsolder the red wire from the battery tab and solder the anode ( non band end ) to the red wire, and solder the cathode ( band end ) to the battery tab. That's pretty much it. It all tucks inside neatly.
A word of caution, the red wire does not have much slack, don't want it to disappear into the body. It seems you also can not pull on it much. When I first finished the mod the meter was way off. When I investigated, I was seeing full battery voltage at the meter. In the end, I added some wire to give some slack and then it worked fine. My service manual does not show how this is wired inside, so I'm not sure what the cause of the issue was, only that loosening things up made it work.
When all was done and working, the F1s meter seems to be with 1/3 stop of an FE2 I compared it to.
I will get out and put a roll of film through it but I expect it will be fine. Now I just use Silver batteries and an O-ring.