Pentax K-1000 light meter circuit?

[BradS]

I remember that when it came out in 1976(?), one of the selling points of the KX was that its light meter incorporated silicon photo diodes. At the time, the K-1000 light meter was still using CdS cells.

Did the light meter in the Pentax K-1000 ever incorporate silicon photo diodes? or was it always CdS cells?

 

[Dennis-B]

I saw a later model K1000 at a show recently, and it still had the Cds photocells. I don't think they ever changed.

 

[Paul Howell]

I have one of the later model chinese built bodies, it has the CdS cell. As I recall the changes over the years was to less costly materials, such as plastic, I doubt that more expensive silicon cells expense were used in the later models.

 

[benjiboy]

I recall the Pentax K1000 had no meter switch and relied on the lens cap being on to stop the batteries from draining.

 

[ic-racer]

 

[vlasta]

Did the light meter in the Pentax K-1000 ever incorporate silicon photo diodes? or was it always CdS cells?

Never, only CdS.

 

[BradS]

...schematic diagram..

Thanks for the schematic diagram! Its a simple but pretty interesting circuit. The two adjustable resistors, J209 and J210 in the diagram, must be the two that are accessible through the little holes under the rewind crank trim piece.

Do yo uknow or can you speculate whether the circuit changed over the long production cycle? and if so, what time period does this schematic represent ?

 

[BradS]

Oh, and most importantly, does how does this circuit compare to that of say, the Spotmatic SP-II ?
Obviously, they're not the same because the Spotmatic has an meter on-off switch and does not do open aperture metering....