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

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Andreas Thaler

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Problems with the automatic aperture on the Minolta XE are described here, everything is very similar to the R3:

Minolta XE Group

This group is dedicated to providing a place for Minolta XE series photographers to exhibit quality work. We welcome as submissions any photographs taken by a Minolta XE-7 camera as well as any photographs of a Minolta XE series camera (using any type of camera, even digital). The group will be...
www.flickr.com


That means I can continue researching the XE, which is obviously more popular than the related R3 and there is also the service manual for it, at least.
 

miha

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Andreas Thaler said:
I am sorry @miha, it would have been nice if the problem had already been solved.
Click to expand...

It's not a problem, one can't have it all I use it in manual and selective metering (a matter of choice) and in this way the camera works flawlessly.
 
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Andreas Thaler

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The recommendation here is to treat all pots on the prism with electronic cleaner:

Minolta XE Group

This group is dedicated to providing a place for Minolta XE series photographers to exhibit quality work. We welcome as submissions any photographs taken by a Minolta XE-7 camera as well as any photographs of a Minolta XE series camera (using any type of camera, even digital). The group will be...
www.flickr.com


I thought about that too, but didn't pursue it further because I thought the problem had already been solved.

Anyway, I'll try it on my patients, I hope they have the same fault

I haven't found any concrete information about the cause of the problem with aperture priority mode.
 
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Andreas Thaler

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miha said:
It's not a problem, one can't have it all I use it in manual and selective metering (a matter of choice) and in this way the camera works flawlessly.
Click to expand...

Do I understand correctly that aperture priority mode does not work in both measurement modes (integral and selective)?

But the exposure meter always shows correctly in both modes and you set the shutter speed manually?
 
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Andreas Thaler

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I'll also take a look at that one tantalum capacitor.

That's at least an approach, I would prefer to know what is causing the error.

We‘ll see.
 
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Andreas Thaler

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The „Exposure interlocking system“ (memory) of the Minolta XE is described in detail over several pages in the XE service manual.

My understanding is that this system is part of the aperture priority mode.

It's worth working through it. Of course nothing is easy there.

Among other things, the camera stores the exposure value in a capacitor (C1), since measurement is no longer possible after the mirror is folded up. This should be the tantalum capacitor mentioned, which is at least easily accessible in the related Leica R3 MOT.

So I'll start there and I'll check the capacitor later.

From page 15 (PDF numbering):

 
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miha

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Andreas Thaler said:
Do I understand correctly that aperture priority mode does not work in both measurement modes (integral and selective)?

But the exposure meter always shows correctly in both modes and you set the shutter speed manually?
Click to expand...

Correct.
 
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Andreas Thaler

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In the service manual for the Minolta XE, I identified a total of three tantalum capacitors on the two boards A and B, which should be accessible with a little disassembly.

They are therefore part of the Exposure interlocking system (memory) for automatic operation (aperture priority mode).

If something can break over time, these three capacitors are candidates. So I'm pinning my hopes on these three and will try to measure/replace them.

It's definitely worth a try, and I hope that these three capacitors can also be found in the R3.

Basically an attempt to work on two camera models in parallel


Conclusion
  • I am assuming that the Leica R3 MOT and Minolta XE are similar in terms of circuitry.
  • The three tantalum capacitors in the XE can be electronic components that lose their standard values over time. Since they play an important role in storing exposure values in Aperture priority mode, they are the first suspects.
  • Whatever the outcome trying to fix aperture priority mode, it will be educational. If I have already understood some of the electronic controls, I'm happy.
  • I can only do the troubleshooting based on suspicion because I don't overview the circuit.
  • It should not be possible that the potentiometers have adjusted themselves. More like oxidation, like with the switches. Electronic spray should help here without changing the pot settings.
  • There are adjustment procedures for the potentiometers in the service manual, but these require specific test equipment.
  • With that, for my part I'll close the topic and get back to you.
  • At least @miha can now work with his R3 MOT (measuring needle no longer jumps), so 50 % of the goal has been achieved. Anyway
  • I won't be the one to solve the problems, more competent people have probably tried that, but I'll try
 
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Andreas Thaler

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It's worth stocking up on supplies, in this case new electronic components.

Here is the replacement for the three tantalum capacitors in the Minolta XE at 2.2uF, 1uF and 0.22uF:



I don't know if the size will fit, but I can solder them tentatively onto the two boards.

Now I just have to find a Minolta XE here that also has problems with aperture priority.

Next steps:
  • Remove the top cover from the Minolta XE.
  • Remove both circuit boards.
  • Measure the three built-in capacitors and
  • definitely replace them.
  • Check whether the replacement of the tantalum capacitors achieved anything.
  • If so, I can transfer the knowledge gained to a Leica R3.
  • I work with the Minolta XE because I have the service manual for it.
 

herb reikers

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Guten Tag Herr Thaler!
Bitte kann ich sie um Rat fragen: Ich habe zur Reparatur eine R3 Mot bei der das Seil für die Blendenübertragung heraußen ist wie an Ihrem Bild oben.
Ich kann nicht finden wie man das Seil in die Rolle(n) zwischen den Schlitzen bekommt. Auch bei abgeschraubtem Bajonett sehe ich keine Möglichkeit die vordere Umrahmung abzunehmen. Es sieht aus als ob es ein Stück mit der Frontplatte ist.
Könen Sie mir bitte einen Tipp geben wie ich das Seil da wieder hinein bringe? Ich bin zwar versiert mit kamera Reparaturen, aber da komme ich nicht weiter.
Danke für einen Rat, herb reikers
 
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Andreas Thaler

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Hallo Herb,

danke für deine Rückmeldung!

Da es schon etwas länger her ist, dass ich mich mit der R3 MOT beschäftigt habe, muss ich mir das wieder ansehen.

Ich melde mich!


Hello Herb,

thanks for your feedback!

Since it's been a while since I looked at the R3 MOT, I'll have to take another look at it.

I'll be in touch!
 

herb reikers

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Thanks for your answer! I'm looking forward to get your reply. I hope you can give me advise to solf my problem.
 
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Andreas Thaler

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Leica R3 MOT ELECTRONIC







The cable guide on the top of the left housing part (please ignore the arrows).






The loose cable in the mirror box and rear view for overview.




Removal of the bayonett ring.




Below the support for the bayonet ring there are four screws for attaching the mirror box.




Mirror box unscrewed.




Now the two rollers for the cable are accessible.


I would attach the rope to the two rollers by pulling on and fixing it on the outside with adhesive tape and then reinstall the mirror box.

Certainly not an easy task.

But on the rest of my R3 MOT the cable is cut, so in your case there might be enough tension to get the cable taut on the rollers.
 
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