Possible meter problem with my Spotmatic

[malkav41]

Hey all, I recently picked-up a Asahi Pentax Spotmatic SP w/ a Super-Takumar 1:2/55mm lens, and a Sears 1:4/70-210mm macro/zoom at a thrift shop for 15 bucks, and after cleaning it up, and finally finding a battery to power the meter, I've loaded it with a 12 shot roll of 400 iso for testing.

Well, there seems (to me) to be a problem with the meter. I put a #392 silver-oxide battery in to power the meter, it is in the correct way (negative side toward the cover), and the meter dives down as it is suppose to when checking it at B and 100 iso as per the manual.

Here's where the possible problem comes in. With the Sup-Tak 55mm on the camera I only get meter needle response at speeds between 1/125 to 1/1000 outdoors through the F-stop range on the lens (F/2-F/16), at 1/60 and below the needle pegs itself in the upper part of the meter scale (overexposure zone), and no matter what F stop I set the lens at, it stays there. With the Zoom it's the same.

So I was wondering if this is normal with the Spotmatic, or a sign that the meter is toast.

If this is the wrong place to ask this please feel free to move it to the correct place.
Thanks in advance for any answers I receive.
Ed

 

[Dwig]

It sounds like an internal problem with the metering system.

The battery you are using is not the correct battery. The correct one is no longer made. The modern substitures will require some recalibration of the meter. Still, the meter should function at a wider range of shutter speeds.

Does changing the ASA to 25 change the shutter speed range where the meter functions?

 

[malkav41]

Well, at ASA 25 I can set shutter speeds from 1/30 to 1/250 in bright light, but at 1/30 I have to set the F stop to 16 to get the needle to center, after that the needle centers between 5.6 and 4 at 1/60, 2.8 at 1/125, and 2 at 1/250.

And it's pretty much the same thing at ASA 100 allows speeds from 1/125 to 1/1000, and ASA 200 from 1/250 to 1/1000.

So it definitely looks like the metering system is on the last train for the coast.

Well, I hear good things about "Sunny F/16". At least till I can maybe afford to get it fixed.

 

[Dwig]

Well, at ASA 25 I can set shutter speeds from 1/30 to 1/250 in bright light, but at 1/30 I have to set the F stop to 16 to get the needle to center...

... which is about the correct exposue for ASA 25 in full sun.

There still seems to be an issue with the coupling range. The meter should function over a wider range of shutter speeds than just 4 covering a 3 stop range. There is some problem, possibly a cracked resistor ring what works when the contact is on one side of the crack and fails when you change shutter speeds to the point that the contact moves across the crack onto the dead section. The ASA and shutter speed are mechanically linked so this fits with the functional shutter speed range shifting in sync with an ASA change.

 

[compur]

From your description the meter is working correctly.

The meter is indicating over exposure when you select aperture/shutter speed
combinations that would produce an over exposure in bright sunlight.

 

[malkav41]

Thank you both for the replies.

I just recently re-found my Pentax Spotmeter V, and wondered if I could double check the meter's readings with it, or is a spotmeter to limited?

I also have an old GE exposure meter from the late 40's, but it measures in foot candles, and the shutter speeds are a bit different (120 seconds to 1/800). It does use American Standard speed numbers though. It was for film or plates.