Bttery Replacement of Pentax V Spotmeter

[Michael Heald]

Hello! I just purchasesd a used Asahi Pentax V spotmeter to use with my 4x5 Tachihara. I need to purchase batteries, since it used mercury batteries, and I see from previous posts that the LR44 batteries should work.

Have members found other replacement batteries also work with this spotmeter?

Should I check the accuracy of the meter with the new batteries, since the voltage is slightly different from the old mercury cell? Would a step wedge work, if the meter needs to be checked? Thank you and best regards.

Mike

[Leonard Evens]

I don't have any experience with that particular meter, but I do have an old Honeywell/Pentax spotmeter made by Asahi. My meter used a 9 v battery for low level light and a mercury cell for high light. There is a 1.5 alkaline battery which fits in the space for the mercury battery, but the voltage is considerably different. I found that I could not use a 1.5 v battery in my meter. The problem is that the scale is not linear so the errors are different in different parts of the range. You would have to do a careful calibration against a reliable meter for the entire range of high values and compile a correction table. In practice, it would be awkward to use, I think. My best choice for this camera was a Wein Cell MRB625, which is a 1.35 v battery. It doesn't fill the space, but I improvised a conducting filler from coper wire. Also, the voltage was still not quite right, but the maximum error was something like 1/2 to 2/3 stop. The main problem was that when it failed, it still passed the check mechanism which was to compare 10 in both the high and low readings. The only way I knew the battery had failed was that the high readings were far off. I finally gave up and got myself a Pentax Digital Spotmeter, and I've been happy with it ever since.

If you want to do a careful calibration, I would suggest finding large uniformly lit surfaces at different intensities and measure both with the spotmeter and with the other reliable meter, using the spotmeter to check the uniformity of the lighting. I wouldn't try to do it with step wedges.

[Doug Pollock]

I purchased a PX640 BATTERY ADAPTER off that auction site for $21.00 It fills up the battery compartment after inserting commonly available button batteries. Accurate. Simple. Reliable, so far.

[tim atherton]

I thought the Spotemeter V took three (G-13 type) 1.5 Mercury batteries.

I've always just used three 1.5 silver oxide batteries with no problem....

[Keith Fleming]

You might check with your local Radio Shack store. As I remember, there is a battery that is equivalent in size to three of the 1.5 volt batteries--and the voltage is 4.5 volts. I don't know if that's the PX640 mentioned earlier.

[Wayne]

My Pentax V manual is about 20 years old, and it specifies G-13 silver batteries

[ronald moravec]

The older meters did not use the 3 - 1.5v battery pack.

Bite the bullet and get the digital spot meter.

[Tom Westbrook]

Mine has 3 Energizer 357's in it now and work fine. Those are silver oxide. I've also used A76 or D76A's (same as G13), too, but those are the alkaline version and won't last as long and don't do as well in the cold. Here's a handy conversion chart: http://www.kassoy.com/watch05.html.

[Michael Heald]

Hello! I put in three LR44 1.5 volt batteries, and it has powered up fine. Now to run some tests, and to check it for consant signal as the batteries wear down. Best regards.

Mike

[tim atherton]

you may have to wait a bit - I think I've had the same set in for at least 2 1/2 years....