Bronica 75mm f2.8 MC repair

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John Hendry - 27 Feb 2004 03:40 GMT

Hi,

I have some issues with a Bronica 75mm f2.8 MC lens for an ETR. The shutter
is intermittent, and there are some growths around the edge of the inner
surface of the front element. I'd like to disassemble the lens and
investigate and rectify these problems. I got the front cone with the lens
name out with a rubber barrel, and the rear plate removal was equally
obvious. Anyone know how I proceed from here? I've had rubber rings and lens
spanners on the front and rear elements but they are very solid - I presume
they unscrew anticlockwise. I found two locking grub screws on the rear lens
cell, but removal of these didn't seem to free the thing. Just a thought,
but is there any way to release the lens/shutter assembly from the barrel in
one piece to gain better access?

Any advice on the correct disassembly sequence, or a service manual source
most welcome,
Thanks,
John

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Mike - 27 Feb 2004 03:51 GMT

The front section of the barrel will come off in one big piece. Remove the
three or four screw around the barrel, back out the screw in the T switch
till it stops then lift off the front section. The front and rear lens
assemblies come out in one piece each the problem is that Bronica puts a
loc-tite material on the threads. The best method of removal is a flex clamp
wrench or a hell of a grip. I would suggest not attempting to disassemble
the lens. The intermittent problem is usually the internal cocking ring on
the back of the shutter.
Removing the ring raises more issues.
Mike

> Hi,
>
[quoted text clipped - 14 lines]
> Thanks,
> John

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John Hendry - 27 Feb 2004 04:22 GMT

Very useful info. Thanks Mike. I notice the rear element seems to reside
inside a sleeve of equal height but with a 1mm or so clearance. Does this
sleeve unscrew by itself or does one have to leave it and get the rear cells
out from the top using a lens spanner? I've had a rubber strap wrench on
this to no avail. A tiny amount of penetrating oil overnight might help I
suppose.

> The front section of the barrel will come off in one big piece. Remove the
> three or four screw around the barrel, back out the screw in the T switch
[quoted text clipped - 6 lines]
> Removing the ring raises more issues.
> Mike

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Mike - 27 Feb 2004 05:16 GMT

With the lens racked all the way in the rear lens assembly protrudes enough
to get a flex clamp wrench on it. I don't use spanners because they can
slip ......into the glass.
No need to remove each cell. You might try a little acetone or toluene to
soften the loc-tite, penetrating oil by its very nature is corrosive.
Once you have the lens groups out you can clean the threads with toluene or
a Loc-Tite solvent this will make reinstalling the glass much easier.

> Very useful info. Thanks Mike. I notice the rear element seems to reside
> inside a sleeve of equal height but with a 1mm or so clearance. Does this
[quoted text clipped - 15 lines]
> > Removing the ring raises more issues.
> > Mike

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John Hendry - 27 Feb 2004 10:28 GMT

I have a little acetone to hand so will try that to loosen the locking
compound as you suggest. I've removed the locking grub screws from the outer
barrel of the rear lens cell assembly - I'm not clear as to wht they
actually do - should I replace them before attempting to unscrew the cell do
you think? Apologies for the ignorance but I never had one of these cameras
before, but one thing really mystifies me. When the ETR body is set to
single exposure mode with an empty back it won't advance the frame counter
and cock the shutter. I've examined the back quite closely and can't for the
life of me fathom how the back registers that there is a film loaded and
will start the frame counter and shutter cocking sequence. Can anyone
explain how this is achieved?

> With the lens racked all the way in the rear lens assembly protrudes enough
> to get a flex clamp wrench on it. I don't use spanners because they can
[quoted text clipped - 28 lines]
> > > Removing the ring raises more issues.
> > > Mike

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Mike - 27 Feb 2004 15:06 GMT

> I have a little acetone to hand so will try that to loosen the locking
> compound as you suggest. I've removed the locking grub screws from the outer
[quoted text clipped - 7 lines]
> will start the frame counter and shutter cocking sequence. Can anyone
> explain how this is achieved?

The rear lens is removed in one piece you do not need to remove any screws
to remove the lenses. There is no way I can show you here how to unscrew
the front and rear groups. All I can say is that they each come out in one
piece.
As film is moved thru the magazine it rotates a roller at the top of the
insert which in turn drives the counter, no film no rotating roller.

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