Hi, I'm new here. I recently bought a couple of OM-1s, 2 50 1.8, 1 35 2.8 and the 135 3.5. And I'm delighted with them. These are the best SLR 35mm street camera I have known. I would like to know how you have dealt with the old mercury battery problem that are no longer available?
I just recently sold my last OM-1, but prior to that I took two approaches.
For my first OM-1, I purchased an adapter, similar to the CRIS adapter, that makes use of smaller, G12 size silver oxide cells. The housing of that adapter (on the outside) is the same size as the 625 batteries the camera was originally designed for. The inside is the right size for the silver-oxide G12 cells. That adapter includes a diode which drops the voltage from the silver oxide cell (1.55V) to the necessary 1.35V. That worked really well.
For my second OM-1, I purchased from Jon Goodman (interslice on eBay) an adapter that makes use of smaller, 675 zinc air hearing aid cells. The housing of that adapter (on the outside) is the same size as the 625 batteries the camera was originally designed for. The inside is the right size for the 675 zinc air hearing aid cells. That adapter does not change the voltage - it just feeds the voltage from the zinc air cell (1.4V) to the camera. That adapter was less expensive than the silver oxide cell adapter and also worked really well.
The silver oxide cells last much, much longer than the zinc air hearing aid cells, but the hearing aid cells are much, much cheaper. Both silver oxide and zinc air have very consistent voltage characteristics, so the cameras' meters both worked very well.
If I didn't have the adapters, and I bought another OM-1, I would send it to John Hermanson at Camtech (zuiko.com) and have him do his standard maintenance overhaul, which includes adapting the camera for current silver oxide cells.
Twice today I've come across the same problem. Camtech <zuiko.com> will include the conversion to silver oxide batteries as part of his standard overhaul. He also sells the MR-9 adapter which does the same thing as his conversion, which is to put a diode in the battery circuit that limits the voltage. The MR-9 sells for under $40. If you google MR-9 you will find the importer, and you may buy directly from them, for about the same price. However, if your older OM hasn't been overhauled, you should check out <zuiko.com> and think about sending it in for new light seals, and more importantly, removal of the foam that surrounds the prism on OM-1 and OM-2 series cameras. People think that there's fungus in their viewfinder, but it's foam coming apart. Oh, and by the way, the MR-9 will work for a lot of older spot meters and other equipment that used the old mercs. hope this helps, puptent