Olympus 35 ECR battery--

RLangham · Jan 20, 2021

So the 35 ECR is a programmed autoexposure rangefinder camera from 1972, about two steps up from the more well-known Trip 35. It takes two PX640 mercury batteries, which I've only seen once before.

Now, I just bought one to sell, $10 USD from a thrift store, but I'm considering keeping it.

Right now, I don't want to order batteries and wait a month or more for them to get here if I'm going to end up selling it. I want to know what the best stopgap short of ordering PX640A batteries is. I have tested it with four 357/LR44 silver oxide cells (the battery cover holds them in place well), but I'm quite conscious that this voltage may be way too high to give a proper exposure. What would be preferable? Two PX625A's on one side and something to bridge the contacts on the other side? Or two LR44's for that matter? I'm unclear what the voltage on the PX640 is, and I'm not entirely clear on how the voltage stacks or does not stack with multiple batteries in series.

AgX · Jan 20, 2021

Any mercury cell is fine that somehow fits into the compartment.

The same for hearing-aid batteries, though their voltage may be a tiny bit higher and they got that life expectancy issue once opened.

RLangham · Jan 20, 2021

AgX said:
Any mercury cell is fine that somehow fits into the compartment.

In the US importing them is a felony and they cannot be manufactured. I basically only have Zinc Air, Silver Oxide and Alkali cells available in 357 size and only Alkali in PX625 size (which is the same diameter as the taller PX640 cell).

AgX · Jan 20, 2021

I never imported any mercury cell. But found them in cameras I bought.

I have not got cell sizes at hand, but your one is a fairly big one, thus your way by lack of fitting an apt one then would be to adapt a smaller cell to fit and get contact. Think of bending original contacts or making springs from brass or make paddings of folded aluminium foil. As long you are sure of not provoking a short circuit.

RLangham · Jan 20, 2021

AgX said:
I never imported any mercury cell. But found them in cameras I bought.

I have not got cell sizes at hand, but your one is a fairly big one, thus your way by lack of fitting an apt one then would be to adapt a smaller cell to fit and get contact. Think of bending original contacts or making springs from brass or make paddings of folded aluminium foil. As long you are sure of not provoking a short circuit.

Well, if I had four PX625A's on hand they would fit perfectly into the space of two PX640's--two of the double 357's (I don't know what they're called) could be held in place, and right now I have four single 357's in it, which over the course of the day have apparently died enough to stop lighting the battery check light. I'm just trying to figure out how to supply the correct voltage and amperage to the meter to get a reading that's at least off by a predictable amount, and such that I don't flatten my batteries in a single day like this.

Quendil · Jan 21, 2021

With mine I have used brass adapters and the zinc air batteries.

These ones
https://cameramill.co.uk/product/ca...640-epx640-v640px-h-n-e640n-mr52-nr52-1126mp/

I have also seen the adapters on ebay

RLangham · Jan 21, 2021

Quendil said:
With mine I have used brass adapters and the zinc air batteries.

These ones
https://cameramill.co.uk/product/ca...640-epx640-v640px-h-n-e640n-mr52-nr52-1126mp/

I have also seen the adapters on ebay

How has it worked? I haven't developed anything yet. Do you find the battery check light always works? On mine it barely did when I loaded four fresh batteries in it, and over the course of the day it stopped showing the light all together.

However when I took the film out and looked through the lens at various light and dark areas while releasing the shutter, it seemed to be choosing what looked like reasonable apertures and shutter speeds for the light conditions. But I would have no way of knowing how precise it was. That roll of film was then ruined when the canister (bulk rolled film) worked its way open in my pocket and the spool came out. I got like twenty of these rubbish canisters for thirty bucks...

Chan Tran · Jan 21, 2021

RLangham said:
So the 35 ECR is a programmed autoexposure rangefinder camera from 1972, about two steps up from the more well-known Trip 35. It takes two PX640 mercury batteries, which I've only seen once before.

Now, I just bought one to sell, $10 USD from a thrift store, but I'm considering keeping it.

Right now, I don't want to order batteries and wait a month or more for them to get here if I'm going to end up selling it. I want to know what the best stopgap short of ordering PX640A batteries is. I have tested it with four 357/LR44 silver oxide cells (the battery cover holds them in place well), but I'm quite conscious that this voltage may be way too high to give a proper exposure. What would be preferable? Two PX625A's on one side and something to bridge the contacts on the other side? Or two LR44's for that matter? I'm unclear what the voltage on the PX640 is, and I'm not entirely clear on how the voltage stacks or does not stack with multiple batteries in series.

Use 2 silver oxide batteries and put a metal tube to make up for the height.

RLangham · Jan 22, 2021

Chan Tran said:
Use 2 silver oxide batteries and put a metal tube to make up for the height.

Dead silver oxide batteries as spacers? I have done something similar with a spot meter that wants two PX625's where I put a dead mercury cell and a live alkali cell (which should put out almost as much voltage as both cells, at first) and only had to compensate by one stop.

Chan Tran · Jan 22, 2021

RLangham said:
Dead silver oxide batteries as spacers? I have done something similar with a spot meter that wants two PX625's where I put a dead mercury cell and a live alkali cell (which should put out almost as much voltage as both cells, at first) and only had to compensate by one stop.

I don't think so because dead cell increases its internal resistance and thus would impair the power delivery.

RLangham · Jan 22, 2021

Chan Tran said:
I don't think so because dead cell increases its internal resistance and thus would impair the power delivery.

Then the behavior of my spot meter is very odd. I had already thought so. What's interesting is that while the spot meter internal battery check did not show anywhere near full battery, it did meter within a stop of the correct EV when in high range (for outdoor daylight metering) and I'm not entirely sure that it didn't meter mostly accurately in low range too.

It may well be that in using alkaline to replace mercury, the resistance of the dead cell is useful in bringing the voltage down to the same range as the mercury. I doubt whether this would be the case for the Olympus camera, as I think it draws more power from its batteries and requires a more specific voltage to expose accurately. it's an elegant looking camera but I find the mechanism to be an elegant compared to some other autoexposure cameras of the same vintage.

Quendil · Jan 22, 2021

RLangham said:
How has it worked? I haven't developed anything yet. Do you find the battery check light always works? On mine it barely did when I loaded four fresh batteries in it, and over the course of the day it stopped showing the light all together.

However when I took the film out and looked through the lens at various light and dark areas while releasing the shutter, it seemed to be choosing what looked like reasonable apertures and shutter speeds for the light conditions. But I would have no way of knowing how precise it was. That roll of film was then ruined when the canister (bulk rolled film) worked its way open in my pocket and the spool came out. I got like twenty of these rubbish canisters for thirty bucks...

I haven't used it in a while but it worked just fine for me. I did try at first packing with tin foil but the adapters where much easier. I can't remember about the battery check light sorry

RLangham · Jan 22, 2021

Quendil said:
I haven't used it in a while but it worked just fine for me. I did try at first packing with tin foil but the adapters where much easier. I can't remember about the battery check light sorry

It may just be a very dim old mini lamp. Certainly LEDs were pretty new in the early seventies, so I am nearly certain it has a small incandescent lamp.

Actually I think the zone focusing predecessor, the 35 EC, dates back to the late '60s, and except for the rangefinder and some rearrangement of the controls they are the same camera. This would have been pretty soon after Yashica first put indicator lights in a camera viewfinder.

Olympus 35 ECR battery--

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