“Repairing” Autofocus on the Rollei P66
This has got to be a common problem.
I bought a used Rollei P66 medium format projector about 2 years ago. I love it; BUT.
I kept having a problem with the autofocus. I don’t use glass slide mounts for several reasons. I noted that, as cold slides became heated and changed shape, the autofocus would “go nuts”. It would throw the entire field out of focus and grind endlessly seeking a focus. At that time attempts to bring the slide back in to focus would be hindered by countermeasures from the autofocus. This greatly detracted from the slide show.
Finally, I decided to investigate the problem. I really didn’t want to have to ship the projector off for what would probably be a costly repair. Plus, I have a native distrust for the repair capabilities of unknown craftsmen.
The solution ultimately proved simple, and I discovered that the cause of the problem was such that it had to be affecting thousands of other users. So, I decided to post this information on the web.
It took about 3 hours of observation and tinkering to discover the problem and it’s solution; but I’ll stick to the pertinent details in this discussion.
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First, a basic understanding of how autofocus works in most all slide projectors. The basic proper focus is set by the user. The autofocus system then uses a small lens system of one sort or another to read and maintain that user-set relationship between the rear of the projecting lens and the film surface, as the film surface moves forward and back in response to heating by the projection lamp and/or the vagaries of slide position within the projection frame. Thus, the autofocus system does not know or care what the image on the screen looks like. It is only concerned with where the film plane is in relationship to the rear of the projection lens.
The autofocus mechanism of the P66 involves 2 lenses aimed at the center of the film plane. The mechanism will activate a motor that moves the lens and the autofocus mechanism forward and back as the film moves or as a new slide is introduced that is not in the same plane as the previous slide.
The problem, it turns out, is that a 6 X 6 slide that’s not inside glass may bow considerably once heated. Many tend to bow initially toward the projection lamp heat source. The autofocus mechanism then attempts to move itself and the lens back far enough to match that bowing.
Here is where the problem is.
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The autofocus mechanism can not move far enough back to keep it’s preset distance from the film plane. It keeps trying however, by continuing to activate the focus motor till the projection lens is also racked all the way back to its posterior limits. Thus neither lens system is in proper location.
I discovered that there was a small rubber bumper pad that limited posterior motion of the autofocus mechanism by what was probably not more than just the few millimeters necessary for it to be in the proper relationship to a severely bowed slide. By removing that little pad, (It’s just glued on, and easily pulls off with a pair of tweezers.) the autofocus mechanism can move a few extra millimeters and fulfill it’s mission.
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The problem is thus solved.
Of course none of this would happen if one was using glass slide mounts; but many of us only use glassless mounts.
I’m surprised that Rollei would build this flaw into the projector. I’m sure it has frustrated many before me, and it is difficult to diagnose the problem. Maybe the little bumper pad was added by someone else; but I doubt it.
Anyway, I hope this treatise makes others’ lives more pleasant.
God, I love the internet.
Charles Clemens
I just received this follow up tip from a fellow photography nut. It describes further repairs in the same area that others may be having problems with.
“Hi
Charles,
I found your Website as I also
had problems with the autofocus of my P66S. Your descriptions are helpful and
your solution is useful. The problem I had was a little different from that.
The autofocus did not work at all. I was just able to use the manual focus
setting. But as I understood the whole thing, it should compensate any distance
drifts and variations between the slide and the lens (in other words the image
distance). I did not got any schematics, but it is not
too hard for an old repair freak like me anyway.
I
saw, that while manual focusing, the electromagnet above the objective is active
and prevents the autofocus optic from moving. It has a Dual-LDR as a position
detector, and the midpoint of it goes via a mechanical switch to the remote
electronics of the P66S. This switch is normally closed, except when manual focusing
is working, thus it is opened by the above mentioned electromagnet. By correct
function you should be able to measure the voltage of the sensor at the black
wire of the board, and Pin 4 of the connector (from left to right). And this
voltage should change, when you move the slide or the autofocus optic. But I
did not measure this voltage, as the switch was not closed! It probably was
less than a tenth of a millimeter, which was left between the two contacts. So
I bent the lower contact spring upwards, so that the switch really closed again
and still opened by the electromagnet. You also can see the switch on the first
of your pictures.
I
had a second problem: Sometimes slide change was blocked. I carefully took some
silicon oil on mechanical places and changed the belt (I did not buy the
original spare part but just a suitable O-Ring). The old was too smooth from
age. Now the P66S is ready for selling on Ebay.
Regards
I have put the Owner's Manual for the P66s on line at:
http://www.cwclemens.com/Rollei P66s Owner's Manual.pdf
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