Olympus OM-1n CdS cell

[Buko]

Hi,
I have been enjoying my little Olympus for nearly 3 years now, but only aproximately two years ago, when I started developing film by myself I've realized that the exposure meter was aways overexposing by 2-3 stops. Therefore I started using an external meter, but for street photography I find it wery inconvenient. Finally, a few days ago I decided to try solve the problem:
Following the instructions on the original repair manual have taken off the top cover and the pentaprism and I've noticed that one of the CdS cells, the one on the right looking from the back of the camera, is not responding to the light.
What sould I do?
Is there any way to check the contacts on the back of the cell and eventually find a new cell to replace it?

 

[Steve Roberts]

I have little experience of repairing the OM-1n, but you might like to take a look at the thread I started a few days ago titled "Pentax Spotmatic CdS Light Dependent Resistors". It may or may not help you, but some of the opinions should certainly give you a bit of food for thought.
Best wishes,
Steve

 

[Buko]

Thank you,
I see that neither you have not found a solution yet…
I wish that someone could help us.

 

[4season]

If it were my camera, I would remove the good photocell and measure it's resistance both in dark and under very bright light. Then I'd see if any of these are fairly close match within say 20%:
https://www.digikey.com/products/en...tity=&ColumnSort=0&page=1&stock=1&pageSize=25
https://www.digikey.com/products/en...tity=&ColumnSort=0&page=1&stock=1&pageSize=25

 

[Buko]

I don't think they are going to work as the CdS cell in the camera has 3 different wires an these have only two.

 

[4season]

I don't think they are going to work as the CdS cell in the camera has 3 different wires an these have only two.

Trickier but perhaps not impossible: Three wires suggest that each cell contains 2 resistors plus a common lead. If need be, a replacement could perhaps be fabricated from a pair of photocells wired in series.

 

[crumbo]

First, check the wires themselves closely -- they may be pinched or parted. This can easily happen when the hot shoe's "roll bar" is installed.

If the cells need to be replaced, in all likelihood you can simply exchange eyepiece/cell assemblies with a "donor" part from a "dead" body -- impact, liquid, etc. Olympus' quality control was such that response from cell to cell is almost identical, so chances are no significant adjustment will be necessary, so long as you find cells with identical color wires -- and I believe there was only one "type" of cell used in the "N" models.

If you do need to remove an individual cell, just carefully pull the wires out of the glue holding them in place, cut through the glue holding the clear slide over the cell with a small blade, then gently pry the cell out of it's well -- it's held in place with a small dab of contact cement.