I recently received what seems to be a 6 1/4"/6.3 B&L Tessar IIb. I say seems to be because the barrel's f/stop markings start at 4.5, not 6.3 as I expected. With the diaphragm wide open, it really does seem to be an f/6.3 lens, though, its focal length seems to be 6.25" +/- not much, and wide open it puts a better than passable image on the ground glass. So its a little strange.

But it has a very stiff diaphragm. Suggestions, please, on what to do to the barrel to get the diaphragm to move more freely. The cells come right out of the barrel, so treating the barrel with a solvent should be no problem.

Thanks,

Dan

That last sentence needs a comma.... "If they arent (stiff), clean the barrel's surface with your favorite toxic cleaner on a rag or Q tip. No need to soak. The lube with wax (micro-crystaline, turtle, Blue Coral, etc or graphite and re-assemble.

Les


<font size=-1>[ This Message was edited by: Les on 2005-05-22 14:40 ]</font>

Quote:

On 2005-05-22 14:34, Les wrote: That last sentence needs a comma.... "If they arent (stiff), clean the barrel's surface with your favorite toxic cleaner on a rag or Q tip. No need to soak. The lube with wax (micro-crystaline, turtle, Blue Coral, etc or graphite and re-assemble. Les <font size=-1>[ This Message was edited by: Les on 2005-05-22 14:40 ]</font>

Son-of-a-gun! It came apart just the way you said it would. The diaphragm is, as you predicted, fine, there's gunk in the barrel. Now to find some toxic cleaner.

Thanks very much,

Dan

Use our old favourite, Ronsonal. I usually flood clean the blades when they get gummy, but occasionally have had to remove the blades to get rid of heavy debris or to repair a blade that had buckled or lost a pivot pin. Getting the blades back in is a special treat, and I only take them out as a last resort.

As you found, most of the time the "stiff diaphragm" is really old dried grease on the ring and barrel.

I recently picked up a 19" Atar in barrel that was stiff also. I put pin point drops of TriFlow on the barrel collar and used a Qtip to spread (work) microfine graphite along (into) the surfaces (both sides) of the aperture blades and pivoit points. It works "smooth as slik".