It is an open secret that Pentax 6X7 and 67 don’t run without power. While their mirror and cloth curtains are mechanically driven, they are in fact electrically controlled by transistors and a magnet. A TTL prism finder also drains a battery if you forget to switch it off. The most common equivalents to PX28 are well-known alkaline 4LR44 and silver-oxide 4SR44 batteries. While you can find these batteries in some specialized stores, they are not universally available in case you’ll need them urgently.
Making 4LR44 replacement
And it happened to me once… I forgot to take batteries for both my cameras – Pentax 6X7 and 67 – on a trip and was unable to instantly find a 4LR44/4SR44 battery or its equivalent in the town I was staying. Fortunately, I managed to find four LR44 button cells instead of keeping in mind to fix them together with tape and use the whole set as a replacement.
It was a big success to find them so easily and quickly in a nearby store. These batteries are more common in local stores than 4LR44/4SR44. But they are also a bit longer than a set of four LR44/SR44 button cells. So, I needed a spacer of about 4-5mm long to be added to the set.
Considering “what to use as a spacer”, I found an iron screw-nut of similar diameter and about 7mm long lying on a street, which I used as a spacer. The set is 3mm longer than a standard 4LR44/4SR44 battery, but it is still possible to be used as a replacement for PX28.
Well, it was a good experience and the set sufficed for the entire month of shooting and I kept using it upon my return for some time. Honestly, it is better to use original 4SR44 or 4LR44 batteries. I will be happy if my tip helps you in a difficult situation. Wish your batteries never let you down and keep shooting!