Leica R3: Mission Aperture Priority

TPrins

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Interesting!!!
Currently i feel a little lost. I picked it up again to work on the steps Nimbus wrote and suddenly the mirror would stay up after firing. Turns out some wires on top disconnected, so after fixing that i'm suddenly back on track.

- manual times seem to work okay now. 4s is very close to 4s
- automatic times are still up to 10s like you had too.
- C1 looks pretty bad to me. I've got a spare body with water damage, that i could take the C1 of. (2nd photo) Maybe i can measure first if C1 is the problem? How? i got a basic multimeter.
- Since you live in NL too, i'm secretly wondering if you're interested in me shipping or bringing you the body to have a go at it.
- also wondering how you are able to check the manual 500 and 1000 speeds. Do you have a shutter tester?
- Nimbus says, C2 could also be the problem. Is that the flat brown one under the shutter lever?
Thanks for all the involvement in this guys.
 

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Nimbus62

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I think : if you have manual times working, do not change C2 for the moment. I will work on automatic and will not focus on high speed for the moment.
If automatic too long, change the C1 cap. easy and at no risk.
 

jajong

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Hi TPrins, C1 is the beige capacitor under PCB-A (the board on top). C2 is the blue one on that same PCB-A. At least that is what I understood from the XE-1 service manual. I do have a basic shutter tester ( Photoplug, www.filmomat.eu) that plugs into a smartphone (3,5mm plug). If your manual speeds are (more or less) okay, then C2 is fine. C1 is the one that stores the energy in automatic mode needed to close the shutter in time. If C1 cannot store enough energy (I know it isn't the correct electrical term :0) the shutter will stay open far to long, whatever the lightmeter is indicating.
Replacing C1 is not too difficult if you cut off the old one leaving the leads sticking out of the PCB. You can then solder the new one to these leads. I would like to advise you to buy a new capacitor C1 2,2uF 16v is what I used. On Andreas's photo you can see C1 in all its glory: the lead on the left is PLUS.

By the way, my R3 is not yet working completely correctly. On auto 1/1000 caps, so I have to deal with that. And the spot/average switch is not working correctly: the camera is in spot all the time.
 

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TPrins

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Well, i'm back at it again. When firing, the mirror just stays up and won't come down anymore.
I replaced C1 with my spare body with water damage and soldered the other brown cap back too.
But now the mirror just stays up in manual and automatic until i remove the battery, then only B and X work...
 

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jajong

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Hi TPrins, looking at your picture no 2 I see some of the legs of IC1 in the air. Should not the be soldered to the PCB?
 

Nimbus62

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jajong said:
Hi TPrins, looking at your picture no 2 I see some of the legs of IC1 in the air. Should not the be soldered to the PCB?
Click to expand...

All IC1 Pin are not soldered to the PCB.
Pin 9 and 12 were cutted and not connected.

the plat pack is soldered back on top !

Body back in front of you, control PCB on the right,
Pin 1 is on the right / back. Then 2 and 3 to gnd/body gnd / 0V
you count the pin clock wise.


Body front
8 9 10 11 12 13 14



7 6 5 2 3 2 1
Body back.
 

Nimbus62

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C1 is not so small. It is a big one "flying" under the PCB, connected with two long wire
 

Nimbus62

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HI here enclosed the updated figure with the correct Pin number for IC1 ...
 

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Nimbus62

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jajong said:
By the way, my R3 is not yet working completely correctly. On auto 1/1000 caps, so I have to deal with that. And the spot/average switch is not working correctly: the camera is in spot all the time.
Click to expand...

About the spot/average selection: is the switch correctly connected to the knobe? is the travell of the switch OK?

About the 1/1000 in Auto : when displat 1/1000 the requested speed is too high ? or it is another problem?
 

Nimbus62

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Except possible error, looking at your picture, this is not C1 but the Th component in parallele with R4.

C1 is connected with to wire near pin 1 and 2 of the IC.
 

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Andreas Thaler

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I'm wondering how this complex analog circuit is temperature compensated so that the voltage values remain constant even when the temperature changes.

As far as I know, a thermocouple is also built in. Is that related to that?
 

Nimbus62

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The circuit is not complex. It is very simple:
They use 2 current generaotr (to obtain stable performance, idependently from battery voltage)
the current travel trought the cells (one or two bridge according Spot or M
The output of the bridge Uev (go to meter through pin 6) and charge C1 through S2.

When you press shutter button, S2 open C1 have the memory of Uev; S"2 open and stop the meter to indicate "memory" in spot mode

When you trig the shutter, the first curtain start, closing S4. Then pin 5 if IC is connected to 0V; an Ib current is created in Tr12 (C1 provide the voltage to create Ib of TR12 )
the result is an Ic current. This current charg C2. The voltage at pin 10 & 8 of M5128K decrease (the charge is negative). And the shutter stop when voltage reach 3V - 2,5V = 0,5V.
2,5V is the trigger level at pin 6 of the IC.


About, the compensation is very light. It is in parallele with R4.
The compensation as the same effect than moving R5 (speed alignment in average mode). It change the Uev voltage reference (same effect than a small ISO adjustment)
There is no compensation in Spot mode (Leica did not implement). R25 is used in spot mode and there is not compensation.

About the C1 cap here it is (thanks to you for the picture)
LEica use a bigger cap than Minolta because they promote the "MEmory function" in spot mode. In fact this feature exist also in average mode.

Preparing the answer, I discover there is another cap "not documented" in Minolta schema and I do not take care analysing the circuit during reverse ingenering.
I will study and will come back soon. Need to build a test bench with R3 or XE. This cap seems connected
 

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Andreas Thaler

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Thank you!

Could you briefly outline the difference between analog and digital camera circuitry for laypeople?

And where the Minolta X generation of cameras fits in? They already have clocked signal processing, but also analog elements such as voltage tapping via wipers and resistor paths. Anyway such analog/digital conversion elements can probably also be found in newer SLRs.

I'm also asking because the subject of „camera electronics“ always remains obscure.

Manufacturer documentation, for example, is only available for Canon up to the A series, and for Minolta up to the XD.

From then on, there are only block diagrams, since the representation of switching processes in ICs is already too complex to be shown in full.

However, if you cannot understand the circuit in its essence, you will remain in the dark when troubleshooting.
 

Nimbus62

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With a voltmeter, it is easy to test the charg value of C1, it is near 600mV and 700mV for EV9 (1/30 f5,6 100ASA)

If it is 0 or very low you obtain very long exposure time, the meter indicate long speed.
If it is +2,5 the meter indicate >1/1000. It appends when circuuit is open at pin 9 of ICM5129K: RSV broken, RAV broken.

If the metter do not move, check the power (pin 2), there is no current through CDS. Test the average mode because the cells are visible.
Disconnect C1 to see if it is

If the meter indicate a speed, look at C1 voltage.
If OK, change C1, (could be a failure of C1)
If C1 charged and always low speed, test continuity (in Automatic mode, B speed, Shutter Open) between in 5 of TR12/M5129K and GND - chassis. Must be 0 Ohms. No battery needed

If still KO, it could be a problem on S7 with bad trigger voltage in Automatic mode (must be 2,5V at pin 6 of M5128K). It gives low speed in automatic mode.
The measure is more difficult because this part is powered only during exposure time.
The solution is to put battery and to trig the shutter. with this long exposure you have time to measure the voltage at pin 6. Must be 2,5V. If lower check the D, S7 and R9.

I hop you will success.
 
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Andreas Thaler

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OFF TOPIC

I have tried to explain the electronics of the Minolta X-700 in a generally understandable way:

Minolta X-700 electronics: A closer look

I'd like to take a closer look at the X-700's electronics in the coming days. On the one hand, I would like to understand how the circuit basically works, and on the other hand, I am interested in details that can be seen on the flexible circuit board. It's always fascinating to me what...
www.photrio.com
 

Nimbus62

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Hi Andreas, no problem I will draft it "simply". I will open a new topic for that.
 

jajong

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Again about the spot/average switch. The problem I had with it after doing up the bodywork was that it remained in 1 setting (spot, in this case). As Nimbus62 hinted, it turned out to be a mechanical thing: the spot/average lever (under the speed setting knob) was not connected to the switch. I found out why. The switch is on a side-board, which I unscrewed and lifted to clean the switch. When I put it back it turns out you can put it back too low. This is because the holes in the board are larger in diameter than the screws that fasten the board to the body: when the screws are in you can move the board up or down for more than a millimeter before you tighten the screws.
So I solved my problem by holding the board as high as possible, and then thighten the screws.
 

TPrins

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Sorry for the radio silence. I've been busy with work past weeks. I've officially given up. I think i cracked the brown cap under PCB B, so now the shutter stays open for a long time, no matter the setting, and then comes down again.
I'm gonna sell the camera for parts probably.
Thanks for all the input, tips and thinking along with me!!! I've learned a lot in the process.
I'm gonna try and fix a Yashica Samurai 4.0 now.
Bless
 
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