RB67 127mm C Lens: Delayed Shutter Release from Dried Lubrication
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This Mamiya 127mm RB67 C lens arrived in the shop with a very common issue that I find in the Seiko shutters used in the early RB67 lenses, the TLR C lenses and the Universal. The complaint is that there is a delay in the shutter firing after pressing the release button. This is caused by dried lubrication in the shutter cocking/release mechanism. The solution is disassembly of the shutter to remove and clean various parts such as the cocking ring, cocking pinion, main cam, main spring. These parts get a very light but critical application of lubrication.
This particular example probably had never been taken apart and everything was quite tight. The name ring, which is removed with a rubber tool would not release. And, I have the original Mamiya tool that is made from a soft rubber type material. The technique that I use in cases like this is my secret weapon of an Evaporating Carrier Dry Lube. The first photo shows how a small amount is applied all around the filter threads. After the carrier evaporates, the dry lube is left in the threads and the name ring will spin off with the proper tool. Much better than drilling holes in the ring for a spanner wrench (I have seen that done many times)
The video show the symptom of delayed release with the shutter removed from the lens: after manually triggering the shutter there was an eight second delay in the shutter releasing. I actually edited the video slightly to cut down the delay time as it’s not that interesting to look at a shutter not releasing for eight seconds.
