Rollei SL35M Meter Switching Repair

[ic-racer]

Rollei SL35M has a curious series of micro switches to aid in backwards compatibility with NON-OPEN APERTURE metering using the SINGLE-PIN Rollei lenses.

The idea is that when a lens is removed the meter will turn off. If an OPEN-APERTURE lens (so called two-pin lens) is attached, the meter turns on again and open aperture metering is effected via a tapered cam.

If a SINGLE-PIN lens is attached the meter stays off, forcing the user to turn the meter on with the STOP-DOWN button.

The accomplish this logic, there are TWO SPDT micro switches in the meter circuit. One switch is effected by the STOP-DOWN button (S1 in the diagram). The other switch is effected when a TWO-PIN lens moved the open aperture metering lever about three degrees (S2 in the diagram).

For clarity I have pointed out the contacts for the two micro switches with red arrows:

 

[ic-racer]

What had happened on two of my SL35M bodies is that the the contacts of microswitch S2 that are OPEN when no lens is attached became dirty. Perhaps because these contacts are visible in the lens mount and are not protected when there is no lens.

I used some DeOxit on an index card and passed it between the contacts to clean them. Now the meters work on both camera bodies!!

Since this happened to both my SL35M bodies at the same time from a period of non-use, perhaps this mode of meter failure is common in other SL35M bodies.

 

[ic-racer]

I want to point out that the meter circuit does not contain any tapered resistive elements that might go bad with use. How can that be?? The way it works is the shutter speed setting, ISO setting and open aperture setting all mechanically rotate the galvometer.

So, if the meter stops working the failure points would be:
A) dirty micro switch contacts
B) CDS cell failure
C) dirty battery contacts
D) galvometer failure

 

[ic-racer]

 

[ic-racer]

Here is serial number ...930 undergoing the repair.