Leica R3 MOT ELECTRONIC: Jumping metering needle repaired; front panel fixed with LEICA lettering

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Andreas Thaler

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Today I unpacked the Leica R3 MOT ELECTRONIC that @miha sent me some time ago for an attempt to repair.

After practicing on a well-worn R3 MOT for the last few days, I felt sufficiently prepared to get to work.

See the story here describing all the technical details and guesses where the error, a jumping metering needle in the viewfinder, may be:



Miha reported that the metering needle in the viewfinder was jumping around in aperture priority mode.

So I checked the camera for functionality.

Result:
  • Jumping needle in aperture priority mode confirmed.
  • Shutter-speed times in aperture priority mode irregularily longer than indicated, errors often at 1/4 s indicated.
  • All manual times plausible.
  • When measuring selectively, the needle goes down when the trigger is activated.
  • The battery check light on the side of the camera does not work.
  • No change in status after I replaced the two LR44 batteries (1.5 volts) with a fresh 3 volt lithium battery.
Conclusion:

Contact problems



1.jpg


2.jpg


3.jpg


Unboxing


4.jpg


5.jpg


6.jpg


7.jpg


Cleaning all battery contacts thorougly with electronics cleaner including the metal screw-in battery holder that connects the batteries to ground.

Some dirt has come off.


8.jpg


The two LR44 batteries that were in the camera and which I cleaned too should still have sufficient voltage even under load.


11.jpg


The 3 volt battery shows a little more open circuit voltage, but there should be more volts. So it's no longer completely fresh.


12.jpg


The aperture simulator ring which couples to the aperture on the lens and transmits the set aperture to the camera's electronic measuring mechanism.

The transmission takes place with a cable pull. Here I had problems with my practice camera because the cable slipped out of its guide when I played with the ring.

The ring on Mihaโ€™s R3 MOT doesn't run smoothly, so I just turn it carefully against its spring with the Spudger so that the cable doesn't jump out of the guide. But with a lens attached, the rotation of the aperture ring occurs more slowly and in stages.

Cleaning would therefore make sense, but this would require the camera to be deeply disassembled.


9.jpg


The manual shutter speeds are plausible.


10.jpg


Selective and integral exposure metering, a Leica specialty, work.


13.jpg


The battery check light on Miha's R3 MOT stays dark when I press the small button with the triangle.


14.jpg


Anyway the lamp works on my practice R3 MOT.

So I'll swap the lamps later, assuming the lamp on Miha's camera is broken.


15.jpg
 
Last edited:
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Andreas Thaler

Andreas Thaler

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Vienna/Austria
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16.jpg


17.jpg


The area with the suspected contact problems is under the ASA wheel with the exposure compensation.

To get to it, I remove the left part of the top cover.


18.jpg


In order to be able to remove the left part of the top cover, this screw must be loosened. There's a crack in the cover here, so I'm careful.


19.jpg


The cover is off.


21.jpg


20.jpg


I check whether the disk with wipers rotates which is connected to the aperture simulator ring in the mirror box via the cable.

At this point I suspect the error: dirty contacts.


22.jpg


The area from above.

There is a plate with gold-plated contact tracks on the top and bottom over which the wipers slide.

The upper contact track is for the ASA/exposure compensation settings, the lower one is for transferring the aperture values to the camera's measuring system.

Depending on the position of the wipers on the contact tracks, different voltage values arise, which the camera interprets as ASA, correction and aperture values.

Analog electronics at its best ๐Ÿ˜


23.jpg


The contact for the battery check lamp is also located here, which I close by pressing with the Spudger.

Even now there is no reaction, the lamp does not light up.


24.jpg


I remove the bracket and ring with the upper wipers.


25.jpg


To remove the contact plate, these two screws must be loosened.


26.jpg


The lower wipers are now accessible, running against the contact track above. Here I suspect the contact problem.


27.jpg


I thorougly clean the contact tracks and wipers with electronics cleaner.


29.jpg


I unsolder the small battery check lamp, which I assume is defective.


30.jpg


For soldering, the R3 MOT goes into my ESD-safe vice.

Here I can adjust the position of the camera using a ball joint.
 
Last edited:

miha

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I'm thrilled @Andreas Thaler Let me just comment on one of your findings:

Result:
  • Jumping needle in aperture priority mode confirmed.
  • Shutter-speed times in aperture priority mode irregularily too long than indicated, errors often at 1/4 s indicated.
  • All manual times plausible.
  • When measuring selectively, the needle goes down when the trigger is activated. This is normal - the needle retracts when the shutter button is pressed halfway down and locks the exposure
  • The battery check light on the side of the camera does not work.
  • No change in status after I replaced the two LR44 batteries (1.5 volts) with a fresh 3 volt battery.
Looks like the surgery goes as planned ๐Ÿ˜€
 
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Andreas Thaler

Andreas Thaler

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Joined
Nov 19, 2017
Messages
1,424
Location
Vienna/Austria
Format
35mm
31.jpg


The intact lamp is unsoldered from my practice R3 MOT ...


32.jpg


โ€ฆ and soldered into Miha's R3 MOT.


33.jpg


But unfortunately the battery control doesn't work either.

I clean the contacts, but since that doesn't help, I rework them with a file and resolder all the associated soldering points that can be reached.

But no success ๐Ÿคจ

In order to investigate the problem further, I would have to remove the top cover over the prism. But that's not without risk; the contact on my practice camera broke when I put it back on.

So I remain committed to my mission to solve the crazy gauge needle problem and leave the lamp dark.


34.jpg


35.jpg


I clean the removed parts as best as possible with isopropyl alcohol and Aqua Purificata.


Success, but โ€ฆ

I reassemble the unit with the contact plate, insert the batteries into the camera and check the meter needle in aperture priority mode.

And actually, the needle is now stationary and no longer jumps around.

The shutter speeds determined by the automatic system now correspond with those indicated and therefore are plausible.

So cleaning the contacts helped ๐Ÿ‘

But at >1/500 the needle continues to jump around like it's drunk ๐Ÿคจ


37.jpg


36.jpg


38.jpg


My last option is to remove the contact plate from my practice R3 MOT and exchange it for the obviously faulty contact plate in Miha's camera.

To do this, three cables have to be unsoldered.


39.jpg


Before soldering the plate, I clean the contact tracks with electronics cleaner.


40.jpg


Soldering the cables wasn't easy because the solder on the contact tracks only bonded in two places.

But after a few tries it worked.


And now the problem was completely solved.

The measuring needle moves smoothly over the entire shutter speed scale and the automatically formed shutter speeds also match. No more jumping.

Wonderful! ๐Ÿ˜Š


0.jpg


I'm pleased that I can now send Miha back an almost fully functioning R3 MOT.

I suggest that we will keep the battery check light as an honorable memory ๐Ÿ™ƒ

This Summicron is from my inventory and therefore remains in Vienna ๐Ÿ˜‰


41.jpg


Especially for @Bearman:

These equipment, tools and materials were used today ๐Ÿ™ƒ
 
Last edited:

miha

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Amazing work Andreas, thank you!! The old Lady underwent a brain surgery and is now fully recovered. Without your engagement this R3 would end as a doorstep - I don't think there are still experts out there that work on old R cameras. With your competence and willingness this Lady was indeed saved. More via PM.
 
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Andreas Thaler

Andreas Thaler

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00.jpg


The tamed metering needle that no longer jumps and that now shows shutter speeds that are actually set by the automatic system ๐Ÿ˜Œ


+++

All information provided without guarantee and use at your own risk.
 
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Andreas Thaler

Andreas Thaler

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Nov 19, 2017
Messages
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Location
Vienna/Austria
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Amazing work Andreas, thank you!! The old Lady underwent a brain surgery and is now fully recovered. Without your engagement this R3 would end as a doorstep - I don't think there are still experts out there that work on old R cameras. With your competence and willingness this Lady was indeed saved. More via PM.

Thank you!

You're welcome, Miha! ๐Ÿ™‚

This was a nice and very educational project for me.

And with this there is hope of getting other Leica R3 and Minolta XE back to work, which otherwise disappear into the closet with โ€žmysterious electronic problemsโ€œ.

Here is the video again that shows how to repair the measuring needle of a Minolta XE.

Big thanks to the author!

 
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Andreas Thaler

Andreas Thaler

Subscriber
Joined
Nov 19, 2017
Messages
1,424
Location
Vienna/Austria
Format
35mm
I'm thrilled @Andreas Thaler Let me just comment on one of your findings:

Result:
  • Jumping needle in aperture priority mode confirmed.
  • Shutter-speed times in aperture priority mode irregularily too long than indicated, errors often at 1/4 s indicated.
  • All manual times plausible.
  • When measuring selectively, the needle goes down when the trigger is activated. This is normal - the needle retracts when the shutter button is pressed halfway down and locks the exposure
  • The battery check light on the side of the camera does not work.
  • No change in status after I replaced the two LR44 batteries (1.5 volts) with a fresh 3 volt battery.
Looks like the surgery goes as planned ๐Ÿ˜€

Thanks!
 

miha

Member
Joined
Feb 15, 2007
Messages
2,591
Location
Slovenia
Format
Multi Format

  • When measuring selectively, the needle goes down when the trigger is activated. This is normal - the needle retracts when the shutter button is pressed halfway down and locks the exposure

In Selective/Spot mode only.
 
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Andreas Thaler

Andreas Thaler

Subscriber
Joined
Nov 19, 2017
Messages
1,424
Location
Vienna/Austria
Format
35mm
  • When measuring selectively, the needle goes down when the trigger is activated. This is normal - the needle retracts when the shutter button is pressed halfway down and locks the exposure

In Selective/Spot mode only.

Confirmed ๐Ÿ™‚
 
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Andreas Thaler

Andreas Thaler

Subscriber
Joined
Nov 19, 2017
Messages
1,424
Location
Vienna/Austria
Format
35mm
  • When measuring selectively, the needle goes down when the trigger is activated. This is normal - the needle retracts when the shutter button is pressed halfway down and locks the exposure

In Selective/Spot mode only.

Your R3 MOT was missing a thin plastic cover disc over the unit with the contact plate.

This disc probably protects the contact tracks underneath from dust and dirt (left side):

000.jpg


That could be an explanation for the contact problem.

Unfortunately, I couldn't use the disc from my practice camera because it has a dent and therefore gets stuck when turning the ASA wheel.
 

miha

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Interesting. The camera had at least two owners before I got it - the first owner's name is even engraved on the camera - so one of them must have it serviced and the disc left out. Anyway I think the camera will live happily ever after even without the disc ๐Ÿ˜ƒ
 
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Andreas Thaler

Andreas Thaler

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I just have looked at the tape underneath the front cover of the prism. The cover hangs down a bit on the left side.

If it's just a missing screw, I'll fix it.

0 3.jpg
 

miha

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It's the broken plastic underframe. But in order to change it, the prism cover needs to be removed. I used a piece gaffer tape to hold it on place. Works since 2008 when I got the camera. ๐Ÿ˜ƒ
 
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Andreas Thaler

Andreas Thaler

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Messages
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Location
Vienna/Austria
Format
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It's the broken plastic underframe. But in order to change it, the prism cover needs to be removed. I used a piece gaffer tape to hold it on place. Works since 2008 when I got the camera. ๐Ÿ˜ƒ

Then I'd better leave it like that. I want to tinker with a working camera as little as possible.
 

miha

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Andreas Thaler

Andreas Thaler

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Messages
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What I can definitely do and without risk is to remove the tape and stick the front cover with the Leica lettering on with Pliobond. This should be sufficiently tight and can be loosened again if necessary. I don't have to remove the top cover on the prism to do this.

 

miha

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What I can definitely do and without risk is to remove the tape and stick the front cover with the Leica lettering on with Pliobond. This should be sufficiently tight and can be loosened again if necessary. I don't have to remove the top cover on the prism to do this.


I would definitely look better than with the gaffer tape :smile:
 

miha

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A diplomatically given order. I take full responsibility ๐Ÿ˜‡
I might not recognize the camera anymore, it will not only undergone a brain surgery but a rejuvenation procedure as well ๐Ÿ˜…
 
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