A warning for those interested in the camera. I recently got a bit interested in photography and bought myself... an Olympus Pen EE2! However, selenium expires with exposure and mine was a dud. (Couldn't test since bought online). If you want to buy one make sure the selenium is still working.
And yes, I took it apart to look for other faults. even tried a recipe to reionize the cells, but it was completely dead. If you buy one a good sign is if it still has the cap.
Would travel to Tokyo.
Would spend excessive time in vintage camera shops.
Would buy this camera.
Would be disappointed if selenium is expired.
How to be sure?
How to fix?
How to replace?
What else to buy?
OG LED watch shop!
Sony/Tektronix o-scopes!
Some older cameras that did have replaceable light meter batteries also used mercury cells which are likely hard or impossible to find. There may be size compatible non-mercury substitutes but they probably won't have the right voltage characteristics to work well.
There are both adapters for Silver-oxide batteries, as well as Zinc-air batteries specifically designed to replace Mercury cells for cameras. See https://shop.criscam.com/products/mr-9-mercury-battery-adapt... and http://www.weincell.com. Some light meters can also be recalibrated or modified to measure properly when using a Silver-oxide or alkaline cell.
I knew that silver-oxide batteries would often work. I had forgotten about the zinc-air hack although they, of course, expire fairly quickly once you start using them.
Mine -- EE3 -- came without a cap but still works! I've been storing it in a case that blacks it out, but this is something that's good to know regardless.
These days it would probably cost less to buy a decent used handheld light meter than to fix an old built-in meter on a camera like the Pen. For years I've used a Gossen Luna Pro with 'spot' attachment.
For anyone else interested in a light meter for an old camera, my coworker's friend developed a small light meter and spot meter that are pretty interesting (and affordable): https://www.reveni-labs.com/
And yes, I took it apart to look for other faults. even tried a recipe to reionize the cells, but it was completely dead. If you buy one a good sign is if it still has the cap.