Re: Mercury battery replacement circuit

[Brian Reynolds <reynolds@xxxxxxxxx>]

Greg wrote:
>
> Saw this on rec.photo.35mm.
> 
> I made my own adapter to use silver oxide batteries.  Here's how:
> 
[snip]
> 
> 4.  Use silver oxide batteries, not alkaline.  I used a shim cut from
> a piece of plastic tubing to get them to fit better.  If your camera
> has a side contact like my Nikon F, you will need to make a metal shim
> from a piece of wire.  I used some Sterling silver bezel wire for
> jewelry making.
> 

The reason for using the silver oxide batteries is that their voltage
drop curve is closer to that of the mercury battery being replaced by
the adapter and battery.

> 5. Insert the adapter into the battery compartment, then lay the
> shimmed batteries over it.  If it doesn't work, try reversing the
> adapter.  It will only conduct current one way (that is the function
> of a diode, the voltage drop is incidental.)
> 

The voltage drop may be incidental to the purpose of the diode in
normal applications, but it is the whole point in the mercury battery
replacement adapter.

I just got one of the CRIS battery adapters for my Yashicamat 124G.
With the alkaline battery that is marketed as a replacement for the
mercury batteries the meter seemed way off.  I'm now testing the
camera with the CRIS adapter and a S-76 (silver oxide) battery.  I'm
shooting B&W test rolls with a grey card in the center of the scene
and shooting frames metered by the camera and by my Pentax digital
spot meter (metered on the gray card).  These will be the first rolls
I've developed in years, and my first 120, and I'm also testing my
Pentax AF280 flash on these rolls.  I figure it's not worth doing a
test unless your fiddling with at least half a dozen variables.  :)

-- 
Brian Reynolds                  | "Humans explore the Universe with five
reynolds@xxxxxxxxx              |   senses and call the adventure science."
http://www.panix.com/~reynolds/ | - Edwin P. Hubble