Mercury battery modification

Radioiron · Sep 9, 2008

Does anyone here know what type of diode is best for converting a camera to use silver oxide cells instead of the old mercury cells, and where you buy them?

I acquired a whole Olympus OM-1 outfit and am looking for options to make it workable. I was planning on simply soldering the diode onto the wire coming off the positive contact. I removed the bottom plate to make sure there was plenty of room to work and I wouldn't have any surprises. I also have acess to my own metal lathe so I could turn out a brass bushing to fit the smaller cell.

I posted this on another forum, but some people where more interested in selling me their hiked up adapter than telling me where to get the diode. This simple task is well within my skill level and I would rather spend 10 bucks on a bunch of diodes I could fix future cameras with than buy an expensive adapter or having to shell out for zinc air cells every few months.

Arvee · Sep 9, 2008

Typically a Schottky diode is recommended, the voltage drop is less than a silicon or germanium. Google 'mercury battery' and you should find some mod instructions. Rather than monkey with it I modified my OM1 with a CRIS adapter. Works great and a lot less hassle. Googel CRIS camera adapter.

You can always use hearing aid batts (675) at about a buck a piece and a #9 O-ring from Home Depot. Hearing aid batts last forever if you don't remove the tape until ready for use but they are only good for 7-10 days through attrition.

-Fred

AgX · Sep 9, 2008

Much has been written on the battery-subject, but the most comprehensive text I found so far (first the dutch original, second the translated version) is:

http://www.stutterheim.nl/rolleigrap...t-adapt-NL.pdf

http://www.stutterheim.nl/rolleigrap...t-adapt-US.pdf

You'll find a graphic showing the voltage fall related to drain for several diodes.

(If you would state where you are situated, I'm sure members will tell you where to get those diodes.)

Radioiron · Sep 9, 2008

I'm in the US, Virginia specifically. I've found articles about the procedures, but searching on the internet I couldn't find any for sale, just the datasheets. Radio shack doesn't have them either, what happened to it being the source for all electronics nerds projects?

Lee L · Sep 9, 2008

Two come quickly to mind:

digikey.com
mouser.com

There are others as well. You may run into minimum order requirements (total dollar amount) that would be a big hit on a small order.

Lee

AgX · Sep 9, 2008

I'm not related to that guy from that pdf at all. But for less than your expected bucks he offers to ship a kit for DIY-making an adaptor. (Perhaps he even sends a different diode to your choice.) You only need an old alkaline cell in addition.

Robint · Sep 9, 2008

In this thread on photonet. http://photo.net/olympus-camera-forum/00QlTh

John Hermanson of Zuiko.com lists the Schlottsky diode he uses to convert OM 1's to 1.5v silver oxide batteries. On googling 1N6263 I find digikey have them for 46 cents

DWThomas · Sep 9, 2008

www.jameco.com is another source for electronic parts. Electronic do-it-yourselfing does appear to be getting more difficult.

DaveT

Ken22485 · Sep 9, 2008

There are excellent instructions on this mod at Dead Link Removed for Minolta SRT cameras, but the principles for your Olympus will be the same.

I bought a 10 pack of the diodes at the big auction place a while back for a very reasonable price. I took a look there now, and it seems most sellers have them in larger quantities - 50 or 100.

If you PM me with your address, I can mail you one.

John Hermanson · Sep 10, 2008

schotkey diode

You can use 1N-6263 diode. From Mouser electronics $0.56 ea 10 at a time. John, www.zuiko.com

AlanC · Sep 10, 2008

Radioiron,

Best of luck to you, you obviously know what you are doing. I don't so I bought a MR9 voltage reducing adaptor from www.smallbattery.company.org.uk This fits in the battery compartment of my OM1 and takes a modern 1.5 volt battery & reduces the voltage down to 1.35 volts.Cost over £20 but worth every penny to me.

Alan Clark

Andy K · Sep 10, 2008

You can also buy (or make) adapters. I used to use one in my OM-1, but last time I sent it for a CLA the company adapted the camera for me and fitted a new battery chamber specifically for silver oxide cells.

Alan C, look up these people, they converted my OM-1: http://www.camera-repair.co.uk/aboutus.htm

AgX · Sep 10, 2008

As I indicated above the diode has to fit the typical drain of the camera as the voltage fall is dependant on the drain. (At least from a theorethical point of view.)
To be sure one could whilst measuring the drain in the same procedure measure the voltage limits within which the camera works acceptable. Then look up whether the chosen diode yields that voltage (see my link above).
But it seems that many cameras work well on standardized adapters/diodes.

Furthermore, there are cameras stabilizing their voltage supply due to their electrical construction.

Excalibur2 · Sep 19, 2008

Radioiron said:
Does anyone here know what type of diode is best for converting a camera to use silver oxide cells instead of the old mercury cells, and where you buy them?

ermm.......my cameras that used old mercury batteries 1.35v, I just use 1.55 v silver oxide and they haven't exploded yet, and anyway surely you can just adjust the ASA if using fussy slide films to correct over/under exposure.

But then maybe cameras like Konica TC, MTL3 etc, are "tougher" than an OM1 and can take an appx 15% voltage overload.

Steve Smith · Sep 19, 2008

Excalibur2 said:
ermm.......my cameras that used old mercury batteries 1.35v, I just use 1.55 v silver oxide and they haven't exploded yet.

An extra 0.15v will not cause any damage to any camera designed for 1.35v cells. What it may do is fool the meter into thinking there is more light than there actually is causing under-exposure.

I get round this by taking a hand held meter reading on a well lit day then adjusting the ISO/ASA setting to give the same exposure settings as the meter.

On the subject of camera metering circuitry, you will quite often see a phrase to the effect of: "this camera uses as bridge circuit so is not affected by cell voltage variances". This is sometimes nonesense as it does not matter if the meter is connected in a simple series arrangement or in a bridge, the voltage across and therefore the current through the meter is a function of the cell voltage in either case.

The only case where this is true is in a camera with a needle which needs to be centered for correct exposure as in this case, the meter used is a centre zero meter which can swing either way depending upon the voltage being positive or negative. The way to check if your camera has one of these meters is to remove the battery/cell. If the meter needle remains at the centre position then your circuit should be fairly tolerant of voltage variations. If it drops to the bottom, voltage will be a bit more critical.

Steve.

Excalibur2 · Sep 19, 2008

Steve Smith said:
An extra 0.15v will not cause any damage to any camera designed for 1.35v cells. What it may do is fool the meter into thinking there is more light than there actually is causing under-exposure.

I get round this by taking a hand held meter reading on a well lit day then adjusting the ISO/ASA setting to give the same exposure settings as the meter.Steve.

Ah! it would seem you are correct about under exposure as I was checking my screw Pentax lenses on a MTL3 (used 1.35v but with a 1.55v cell) and the negs could do with a bit more exposure.......so next time will set 200 asa film at 100 asa.

Mercury battery modification

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