My first post here, hopefully in the right place!

I've just got a Pentax Analogue Spot-meter (the one that takes a 9v and a 1.3v mercury battery). It was a bit beaten up, but was free :-)

Having taken it apart, unbent the needle and cleaned up all the glass surfaces, I find that the low-light range seems to work Ok using a 9v battery.

I now (of course) want to address the mercury battery issue.

Seeing as I have a background in electronic engineering, I am wondering whether it would be feasible to add a 1.3v voltage regulator that will supply the 1.3v from the 9v battery (need to work out exactly what current is required etc., but that should be Ok).

There's plenty of space inside the handle for a voltage regulator (it only needs a few components after all).

Has anyone done this? Are there any pitfalls? (I am assuming that the low/high light circuits are basically independent seeing as the low-light meter looks like it works Ok without the mercury battery).

Thanks,

john..

You might ask Richard Ritter that...he works on them and should know.
http://www.lg4mat.net/

If they share a common negative (or positive) this would work. I would just use a simple resistor and zener diode circuit with a capacitor across the diode. Two ordinary silicon diodes in series would give you around 1.4v too.

I would guess that the current needed was next to nothing.


Steve.