| Author |
Message |
    
Anirban
Tinkerer
Username: Anirban
Post Number: 3
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, October 29, 2006 - 08:04 am: | 
|
Hi,
I have just disassembled a CdS light meter from the seventies (in order to calibrate it), and I notice the photo resistor cell has three pins. I figured out after tracing the circuit diagram that one is a common pin, and the other two are connected to two pots. The other terminals of the pots are then connected together
I have measured the resistances between the two non-common pins of the cell and the common pin (they are 15 kOhm and 35kOhm), Probably the CdS cell is a composite of two individual cells, but I cannot figure out whether these cells are connected in series or parallel.
Have anybody else seen such a photo resistor?
Any ideas would be greatly appreciated.
Thanks,
Anirban |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 36
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 01, 2006 - 07:22 am: |
|
Hi, similar cells were used in the Ricoh 35 Elnicas, for example. I guess they were put in to increase both meter range and sensitivity.
It turned out to be impossible to replace them by two single cells, that is why I gave up all attempts to repair the Ricohs. Besides, I could never find even one such three-pin cell, and that is why I never figured out about the wiring (which would have meant a complete knockdown of the board in the lens barrel), W. |
|
