RB67 Lenses: Testing for Delayed Firing and Oily Shutter Blades
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
get a lot of email and messages on my website regarding repair of RB67 lenses. Not surprising since the RB has been around since 1970 and there is a large amount of these bodies and lenses still in existence. But, many, if not most of them need service if they have not been serviced in the last 20 years. Two biggest issues: 1.) delayed shutter firing 2.) oil contamination on shutter blades.
The delayed shutter firing is easy to diagnose as the shutter simply delays firing after pressing the release button. This delay can be from 1/2 second to several seconds. Solution is disassembly of the cocking/release mechanism, cleaning and a very small amount of proper lubrication.
The larger issue is oil contamination on shutter blades. I tell all my clients to check the lens before sending it to me as this is not a trivial problem to solve without a lot of work.
Here is how to test your RB lens: Photo two shows the back of a lens with the silver release pin at 12 o’clock (my tweezer is pointing to the pin). Photo three shows my thumb depressing the pin while I am holding the two cocking pins with my hands. Then, in the video, I am moving the cocking pins very slowly counterclockwise. Almost as soon as I move the pins, the blades will close. Continuing to move the pins until around the 10 o’clock position, the blades will open for the set shutter speed and then close again. If the blades don’t close down when the sequence first begins then you have oil contamination on the blades.
I make a big point about the oil because this sort of repair takes a bit of time to do properly and can be costly compared to a more limited disassembly and cleaning.. The first photo shows a recent service for oil contamination on a 50mm lens. The final photo in this post shows what the oil often looks like on the blades, but sometimes it is more subtle and hard to see. These issues show up in the lenses made from 1970-1977, later shutters used dri-lube parts so you won’t find the oil problem in them.
