[matsoberg]

My Spotmatic F has been collecting dust for a while and I recently threw in a new Duracell PX625 battery in it. Lightmeter is pointing up no matter what I do. Yes, no matter what I do, until I take the battery out. It´s just stuck there with that battery.

Is the lightmeter broken you think?

Thanks,

// Mats

[titrisol]

I do not have the F, but is there a procedure to test the battery?
maybe is backwards?

[SOldBear]

Similar to the one in the K1000, the light meter in the SPF is always on. The only way to turn it off is to cover the lens.

I have a feeling that the battery is installed backward (reversed polarity). Please check that.

[matsoberg]

Thanks for input guys. The K1000 uses a LR44 or similar battery, but the Spottie F wants a MR-9, PX625 or similar that only fits one way. The battery cover is also marked + (plus) and that´s the only way the battry will fit.

Browsing the net I find there are two versions of the PX625 battery, one 1.35 volt and one 1.5 volt. Could it be the 1.5 volt battery I have gives too much voltage?

Thanks,

// Mats

[raymeedc]

Browsing the net I find there are two versions of the PX625 battery, one 1.35 volt and one 1.5 volt. Could it be the 1.5 volt battery I have gives too much voltage?

Thanks,

// Mats

No. Pentax built a voltage bridge into the circuitry. Either battery will give the same readings.

[monochrome]

Later Spotmatics like the F have a bridge circuit that adjusts to the Voltage of the battery, so you can use either the 1.5 or 1.35 volt, either Silver Oxide or Alkaline. The plus symbol must be facing out when you install the battery.

TO CHECK THE BATTERY

1. Set shutter to Bulb
2. Set ASA to 100
3. If the meter needle is in the UP position and steady the battery has enough power.

Obviously, you must coordinate shutter speed and aperture on the lens for the actual ASA setting to bring the meter needle into the center of the indicator bars.

Check that your ASA setting (might be 25 or 64) is set to the correct film speed.

Check that your shutter is not set on B (Bulb)

Increase the shutter speed and/or reduce the aperture size (higher number) to attain good exposure (needle moves near the center of the indicator).

If the meter needle will not move under any circumstances from the "up" position you have some kind of problem in your meter circuit, but your battery is not the problem.

Go to the following link to get a good pdf of the Spotmatic F manual. The password is always Pentax.

Pentax Manuals

[matsoberg]

Thanks.

Yep, something wrong with the lightmeter in that old baby.

// Mats