RB67 Extension tube flash sync

[powermonkey]

I have a strange problem with one of my extension tubes. Namely, if I'm using my 82mm tube - my flash will not fire. It will work just fine with the 45mm, or with no tubes at all. Is this normal or could something be wrong with my tube?

[fotch]

Do any of your tubes have linkage for the iris for exposure control?

[paul ron]

That shouldn't happen no matter what tube you use since the flash sync is in the lens, independant of the camera n tube.

The only thing I can say is perhaps the tube is not making a full revolution when firing the lens. Check to see if the tube pins rotate freely and complete the rotation when mounted on the camera body without a lens on it. Make a small tic with a pencil to see how far it goes compared with the plain lens mount rotation.