A DIY PX-14 camera battery
While a substitute for the PX-14 mercury cell is commercially available,
it is a less-than-ideal 3v alkaline you may not find immediately in
local shops. Here's how to toss together a 2.7v silver oxide replacement
from parts easily located even in smaller cities. Not cheaper, but quite
possibly better, and definitely more satisfying.
For each DIY-14 you intend to assemble, you'll need two 1N914 diodes, two 357 silver oxide cells and a #23 bonnet packing from the plumbing department. Perhaps already around your home, some fine sandpaper, electrical tape, all-purpose glue, a scrap of solder and a soldering iron. Finally, a multimeter--the stories I could tell you about people who didn't have a multimeter.
Solder the two diodes in series side-by-side and snip the excess leads. Fold a piece of electrical tape over the bodies of the components, trimming excess. (Another narrow piece of electrical tape to separate the two exposed leads is a wise move--permitting any contact defeats their purpose). Wrap one of the exposed leads to the top surface of the electrical tape and the other to the bottom surface. Snip the leads so they don't extend beyond the surface. See Figure 1.
The inside diameter of the #23 bonnet packing is little over half a millimeter too small. Wrap a piece of sandpaper around a pencil and file the interior diameter until the 357 cell just fits. Don't force it. The bonnet packing is more fragile than it appears, and you'll be unhappy if it breaks.
Now, sandwich the 357 cells into the bonnet packing with the diode package in the center. See Figure 2. If you've kept track of the polarity of your diode terminals, good for you. If not, the next step is checking the voltage of the assembly with a multimeter anyway. If it reads 3v, the diode leads are shorted together. If it's next to nothing, the diode package is upside-down, or the terminals aren't contacting the 357 cells. If it's approximately 2.7v, glue the edges of the 357 cells in place. The final assembly needs to be between 15 to 16mm tall.
In theory, the outer diameter of the #23 bonnet packing should be only a fraction of a millimeter larger than the original PX-14. However, outward pressure from the 357 cells may require it to be sanded down a bit more. Do so until you're confident it can be comfortably inserted, and just as importantly, comfortably removed. Painting the sanded area with a thin coat of glue will help supress dust you don't want floating around inside your camera.