[vyoufinder]

I put a battery in my SP500 and the light meter isn't working right. Usually it's not working at all, but when it does the needle bounces to the top and mostly stays there unless I change f-stops... sometimes. Also strange is the fact that when the light meter gives a reading, and it's in the "+" zone, then I give it more light and the needle goes down, not up. I stop it down and the needle goes up to the "+" zone again... Weird. I used the proper 1.35v mercury battery but have seen that some Spotmatics have been converted to use a silver oxide battery.. Is this right? Is this how my light meter would act if mine has been converted?

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Last edited by vyoufinder; 03-06-2018 at 01:17 PM.

[sergysergy]

Is your battery upside down?

[vyoufinder]

Is your battery upside down?

That's what I thought and tried it but it didn't seem to fit the other way. I bought the Wein cell. I might try it again and screw it on to see if it compresses the tab underneath enough to fit. Maybe I was being too cautious. I put the small side of the battery toward the top of the camera, larger base side of battery toward base of camera.. Is that correct?

[Bengan]

You should have the (+) side facing down towards the bottom of the battery compartment.

[vyoufinder]

You should have the (+) side facing down towards the bottom of the battery compartment.

I knew I should'a brought it with me. The manual says "Insert the battery with (+) side toward the top of the camera" Is the manual wrong? I was checking the manual when I installed it. I'm going now to get it and check. The suspense is killing me.

[Bengan]

Insert the battery with (+) side toward the top of the camera

Yes that's another way of saying the same thing. The (+) towards the bottom of the compartment and the (-) towards the compartment cap.

[stevebrot]

Yes that's another way of saying the same thing. The (+) towards the bottom of the compartment and the (-) towards the compartment cap.

What they said ^ ^ ^

BTW...for most purposes your SP500 should be fine with a size-appropriate silver cell*. The voltage difference is inconsequential for most shooting. Oh, and be sure to tape over the vent on the Wein in between sessions to extend its life.


Steve

* https://www.batteriesplus.com/battery/film-camera/pentax/asahi-spotmatic/smc387s

[vyoufinder]

Yes that's another way of saying the same thing. The (+) towards the bottom of the compartment and the (-) towards the compartment cap.

Aha! I did not realize that there was a plastic washer type of thing around the battery cell which, as positioned, made it fit perfectly when inserted backwards. That and the fact that my battery's plus sign indicator looks like a - unless it's in just the right light, then I see it's actually a +. Works flawlessly.

I just love how this thing clicks and will be even nicer knowing my exposure is on/not using a meter. This camera is about 20 years before my time. The ME Super and K1000 are the ones I used a lot but I always liked things made before my time and with a history. My SP500 was serviced by Forster's Camera in SLC, UT in '98 and not been used since. It works like new and is going to be a real pleasure to use.

Thanks!

[sergysergy]

great

[vyoufinder]

Hmm.. Seems it's stuck where the meter reads only from correctly exposed to overexposed. When I drop the light way down, it still says correctly exposed. It seems accurate at bright light (sunny 16) I can use it like this for bright daylight, but not for low light (though still useful as a guide to some extent based on how fast the needle moves.) Maybe it needs a tuning, unless someone knows an easy fix or something I might be doing wrong...?

[stevebrot]

When I drop the light way down, it still says correctly exposed.

What combination of shutter speed, ASA, aperture? As one approaches the lower limits of the meter's sensitivity, linearity suffers. On page 16 of the user manual (free download from HERE) there is a table showing the meter's limits by shutter speed and ASA at f/2 (i.e. Exposure value, EV). The region labeled "B" is of particular interest. Correction must be applied for apertures other than f/2.


Steve

[TomB_tx]

When CdS photocells degrade they lose the dark "high" resistance first, so it is common to underexpose darker scenes, as the meter reads as if it were lighter. I've had that happen on Pentax Spotmatics and other brands, including the Leicaflex SL I bought in 1969. Luckily the Spotmatic cells are likely still available (Eric has replaced a few of mine), and easy to replace, being beside the eyepiece under the top cover.

[vyoufinder]

It's a brand new battery. My light meter only moves from halfway to the top. I found the following picture. Not sure what it's in reference to, but shows the range of motion of my meter. I think it should dip lower than halfway, but am I wrong about this? Nothing makes it dip below halfway (correctly exposed.)

[stevebrot]

It's a brand new battery.

Test it...

1. Shutter dial in "B" position
2. ASA dial to "100"
3. Push meter switch to "On" position while looking through the viewfinder

The needle should rapidly drop to the full negative position. If not, the battery is depleted. Wien cells have a limited life once activated and will deplete whether used or not if the tab is not replaced between sessions.


Steve

[vyoufinder]

Test it...

1. Shutter dial in "B" position
2. ASA dial to "100"
3. Push meter switch to "On" position while looking through the viewfinder

The needle should rapidly drop to the full negative position. If not, the battery is depleted. Wien cells have a limited life once activated and will deplete whether used or not if the tab is not replaced between sessions.


Steve

I did see that in the instructions.. Maybe my brand new battery (still within date) is dead anyway? Just seems hard to believe but I guess my next step is try another. I don't think I'll be buying another Wein Cell.

*edit* I ordered a couple of Energizer 394 silver oxide batteries. One for my Spotmatic too. Plus a couple of Maxell LR41 alkalines I can try since I ordered those first not realizing they were alkaline. Good info: https://www.pentaxforums.com/forums/8-pentax-film-slr-discussion/312360-spot...y-options.html