Stupid damage to a Carl Zeiss 35/2.8 Distagon for Rollei QBM mount

[forest bagger]

Hello folks,

I received a Carl Zeiss 35/2.8 Distagon for Rollei QBM mount for repair whose aperture did not close securely to smaller apertures (higher aperture values).

The oiliness of the aperture blades, which is often encountered, was not the cause!

Instead, the aperture blades were magnetized!

So I had to dismantle the entire aperture mechanism an demagnetize each single blade with a demagnetizing coil.

As I never had this before an the spring ring (the golden shimmering thing in this photo) had scratches in the surface I guess that a former repair man dismantled the aperture an magnetized the blades to replace them comfortably...

 

[grain elevator]

Interesting, I've used a magnet to hold aperture blades in place and thought myself smart, that was a rangefinder lens though, so no quick action needed. I'll try to remember not to do that with SLR lenses.

 

[Andreas Thaler]

Hello folks,

I received a Carl Zeiss 35/2.8 Distagon for Rollei QBM mount for repair whose aperture did not close securely to smaller apertures (higher aperture values).

View attachment 370974


The oiliness of the aperture blades, which is often encountered, was not the cause!


View attachment 370975


Instead, the aperture blades were magnetized!

So I had to dismantle the entire aperture mechanism an demagnetize each single blade with a demagnetizing coil.

View attachment 370976


As I never had this before an the spring ring (the golden shimmering thing in this photo) had scratches in the surface I guess that a former repair man dismantled the aperture an magnetized the blades to replace them comfortably...

Great!

Which tool did you use to demagnetize the aperture blades and how does it work?

 

[forest bagger]

Interesting, I've used a magnet to hold aperture blades in place and thought myself smart, that was a rangefinder lens though, so no quick action needed. I'll try to remember not to do that with SLR lenses.

It's better to add some oil to the blades during mounting so that they stick together. After complete assembling the oil will be washed out by gasoline.

 

[forest bagger]

Great!

Which tool did you use to demagnetize the aperture blades and how does it work?

ELEKTRISCHER TONKOPF-ENTMAGNETISIERER, art.nr. 304856 from CONRAD ELECTRONIC SE

It works. The magnetism vanishes not completely but enough to bother no longer.

 

[Andreas Thaler]

ELEKTRISCHER TONKOPF-ENTMAGNETISIERER, art.nr. 304856 from CONRAD ELECTRONIC SE

It works. The magnetism vanishes not completely but enough to bother no longer.

Interesting so one could use this device to demagnetize other tools like screwdrivers?

 

[Sanug]

Yes, it works.

Question: Why did you deassemble the aperture blades? Why did you not use the demagnetizer with the blades assembled?

 

[forest bagger]

Why did you deassemble the aperture blades? Why did you not use the demagnetizer with the blades assembled?

At first I tried the demagnetizer in the assembled status, it worked not enough.
So I deassembled the aperture completely and demagnetized every single blade separately.

 

[forest bagger]

could one use this device to demagnetize other tools like screwdrivers?

Maybe it will work - however most of my screwdrivers are to strong magnetized for this simple coil.

 

[ic-racer]

I use the head demagnetizer for my audio tape deck when I need to demagnetize things, though I have never encountered magnetized shutter components. Thanks for sharing your experience.

 

[forest bagger]

Since I had one of these lenses yesterday for repair (actually for assembly, since it arrived in two parts), here is an "explosion photo":

In order to access the straight line guide and the aperture mechanism from behind, you have to unscrew the large ring (the middle of the 5 at the bottom of the image) around the rear part of the lens.

This is difficult because it sits very tightly and there is no surface for pliers or similar tools to grip.