Battery Replacement for Yashica Rangefinders
Mercury batteries have been out of production for many years in the US but many cameras that relied on their stable voltage output for metering still exist. One example is the 1.4 volt 625 mercury cell used in cameras such as the original Canon F1 and the Olympus OM1. Not as common is the 5.6 volt Mallory or Eveready 164 cell used in the Yashica Elextro series rangefinders.
Luckily, there's no need to buy fancy battery replacements for the 164 cell. All you need is a standard 6 volt camera battery and a spring. The large size of the 164 cell makes it easy to adapt existing non-hazardous batteries into the same form factor. I used a 6 volt PX28 (or equivalent) battery and a metal spring as a gap filler. I also made a cardboard tube to center the assembly in the battery chamber but this is purely optional and not necessary for proper operation of the camera. The metering seems to be correct so the extra 0.4 volts does not seem to have a noticeable effect (if at all) on the exposure. The picture below shows the simple contraption.
I made this contraption many years ago and have never had a problem using it. The spring was purchased at my local hardware store. It measures 3/4 inch in length (uncompressed), 1/2 inch diameter on the wide end, and 5/16 inch diameter on the narrow end. The cardboard tube is formed by rolling it around the PX28 battery to more than 5/8 inch diameter. The length of the tube is 1-3/4 inches long. The assembly is inserted as shown in the picture above - the negative end goes into the camera body, followed by the narrow end of the spring. There is minimal spring compression; just enough to hold things in place and make good electrical contact.
So there it is. If you have an old Yashica or other camera that uses the 164 cell, don't waste your money on some fancy battery replacement; just roll your own dongle to go use that old camera.