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Martin Miksch
27-Sep-2007, 05:26
I own an old Pentax Spotmeter, it looks similar to the Spotmeter V but is a little different as it has 2 different batteries, 1x 9V block for reading and a smaller one fot the lightning. Now it stopped reading in the upper scale, when I press the L button for low light it works. A dude of mine is willing to repair it but he didnt get clear with it without service manual. So I am looking for a service manual or factory repair manual.
Thanks and Kind Regards
Martin

Leonard Evens
27-Sep-2007, 07:52
If it is like mine, it needs a mercury battery for the high range. None of the available batteries get it quite right, although there is a Wein battery that gets reasonably close. Unfortunately it doesn't fill the space so you need to make something to fill the space while still providing electrical continuity. Even with this battery you can be as much as 2/3 stop off, and you have no warning when the battery needs replacing. I finally gave up and got a Pentax Digital Spotmeter. I recommend that you do the same.

Martin Miksch
27-Sep-2007, 07:55
Leonard, thanks for kind reply. IMO the batterie isnt that problem, mine worked fine with a standard non mercury batterie, now I didnt use it for some month and it doesnt work after that.
Thanks and Kind Regards
Martin

James E Galvin
27-Sep-2007, 08:58
I have frequent problems with mine in that the small battery doesn't make contact. It needs good spring tension inside the battery compartment, a clean latch to make good contact to the base plate, clean and good tension on the spring contact at the side of the battery compartment, and the tripod screw tight. You have to take it apart to tighten the nut at the top of the tripod screw. I finally soldered a flexible wire around the hinge.
Available batteries give a different calibration than the original mercury. There are several adjustments inside that can recalibrate it, easy to do if you have a variable light source and a known meter. Quality Light Metric in LA can do this.

gari beet
27-Sep-2007, 11:49
I have the same meter, and it does sometimes suffer from a poor contact, as has been said a good clean works wonders.

As for the battery I get mine from here, it fits perfect and doesn't need recalibration.

Gari

http://www.brewstersbatteries.co.uk/catalog/product_info.php?cPath=22_53&products_id=193

Martin Miksch
27-Sep-2007, 11:50
Thanks to all of you, Leonard, you are right, I just forgot that the two batteries are used one for low light metering and the other for normal, what a shame. I just ordered a batterie, its not a mercury burt perhaps I can adjust, but maybe this is not that easy without service manual, there are different possibilities to adjust inside. The other thing to try is to bring some kind of diode into the circuit to bring the voltage to 1.3, what the mercury rates. I have a Lunasix 3 and got an adapter from Gossen so I can use ordinary batteries instead of mercuries and this adapter also has a diode or something similar built in to adjust voltage.
James, thanks for the hint, but I am an european resident and so it would be very complicated to send the item to LA, but maybe I can send them an email and they can help me with instructions.
Thanks and Kind Regards
Martin

Leonard Evens
27-Sep-2007, 13:50
The 640A fits very nicely in the compartment, but it has the wrong voltage. If the response of the meter were linear, you could compensate easily, but it isn't. At one point I determined the amount it was off, depending on the reading, and it varied, if I remember correctly, from 0 to 2/3 of a stop. I found it just too awkward to use that way. The Wein battery comes much closer, but it doesn't fill up the space in the battery compartment. I made a coil of copper wire for that purpose, and I got it to work okay. Unfortunately I found that when the battery began to need replacement, the meter just started to read wrong with no other warning. Thus, instead of being at most 1/2 stop off, I was 1 to 2 stops off. With the proper battery, it was completely obvious when the battery needed replacement. The other problem was that the Wein batteries needed to be replaced every few months, whether I was using the meter or not.

As others have pointed out, if the battery is good, the problem is that the contacts are dirty and need cleaning.

I'm sure this meter can be adjusted so that it does work properly, but it sounds as if it would be very expensive, unless you know enough to do it yourself. I would doubt that you can find any documentation about the circuitry at this time. As I said, I just gave up and got a Digital Spotmeter. It has a few drawbacks relative to the optical version, but it is smaller and lighter and generally works better. I have not been sorry I shelled out the dollars to get it.