1/1N pt. 2

OM-1/1N Best Battery: 1.35v mercury (long discontinued) or 1.55v Silver oxide with internal modifications. Weincell (1.4v)causes 1/2 stop error, 625A / U up to 3 stop error, and voltage falls as soon as it is used. MR9 adapter w/1.55v 386 Silver oxide is a good combination. MR9 is listed HERE. Camtech internal battery mod (included free with every OM-1 / 1N overhaul) gives same results as MR9 but you don't have to buy the separate $30 adapter (and no adapter to lose).

All our OM-1/1N repairs include conversion to the 357 silver oxide battery (MS76, KS76, SR44W, G-13, 303). Meter circuit mod includes a diode for stepping the voltage down to 1.35V. The 625A or 625U battery that is sold to unsuspecting buyers is not a real replacement for the mercury 1.35V cell. First, the 0.2V difference causes a 2-3 stop error in the OM-1 / 1N meter. Since it is alkaline, the voltage starts to fall as soon as you start to use it. Any calibration that is done with that battery is almost immediately lost. The zinc-air 1.35V battery (really 1.4V) will cause a 1/2 (one half) stop meter error . If the meter does not work with these batteries, it is most likely because the meter was already defective before the battery was replaced. If you do not want to invest in an overhaul to get your camera converted to the 1.55V silver oxide battery, you can buy an MR9 adapter, which drops into the battery box, and uses the 1.55V 386 silver oxide battery.

Sometimes we see OM-1 & 1N bodies with unusually stiff meter movement. Needle should casually swing up and down. For those that don't move smoothly, here's a close up of a possible meter defect. Note this is only found after the meter movement itself is disassembled (outer metal case slid off the meter movement.) This defect usually shows up after the camera has been dropped.

Found in oldest style OM-1 bodies, this meter can has a small circuit riveted to it. Olympus Japanese techs think this could have been part of an undeveloped battery test circuit or (as suggested by Clint Rhumbo) a switch that closes if the user is trying to center the needle with the meter turned off. The meter turns so far off the mark, that the brushes touch the wide part of the metal pad and the needle goes to the top. Could be! Though my Japanese trainers at Olympus referred to it as "battery check". Meter needle will move with the switch off, and will usually center at asa 100, f1.8 and shutter speed "B".