Leicameter MR-4: Setting the zero position

Hi,

From the manual it is impossible to tell exactly where the needle

should sit in the zero position. My gut reaction is that it should

allign with the line going down to the number zero, However there is

enough leeway to cause the metter to give false readings so I thought

I'd ask what others are using as a guide. I set it as I thought and it

geives me approx. 1 stop more than my Gossen Luna-Pro digital.

 

Thanks,

- Carl

Carl, I brought back 4 out of 6 MR4s from the dead so I kind of got a crash course in MR4-basic. I found that the most accurate way to zero the meter is to take the battery out and then push the battery check button. Then turn the zero adjustment screw so the meter needle straddles the line coming from the zero (or put another way, the zero line points to the center of the thickness of the meter needle). Now you'll have your meter zeroed, but I can't guarantee it will give accurate readings across the meter's entire sensitivity range. If it does, or if it's off the same amount across the range so you can just fudge the ISO, you lucked out. Those CdS cells mellow out with age and require tweaking the resistor pots (there are 2)to get them to read in a linear fashion. While doing that since I had a new PX625A battery in them, I simultaenously calibrated them to the 1.5v.

Thanks Ben, that was very helpful.

Cheers,

- Carl

Carl,

 

Since the owners manual on the MR meter says to remove the battery before zeroing the meter, I would tend to believe Ben's recommendation.

 

Jerry

Ben,

 

How does one get access to the two potentiometers that you mentioned?

I want to calibrate my MR-4 meter to a 1.5 volt silver cell.

 

Jerry

Jerry, I would've RTFM if I'd _had_ AFM, but my six dead meters didn't come with one :(

 

To get to the pots you have to take the top cover off. A pointed-end spanner or probably a pair of strong, pointy tweezers is needed to remove the retaining screw in the center of the ISO dial, then there's 2 regular screws hidden beneath it, plus the 2 little screws on the side below the switch. Then, (THIS IS REALLY IMPORTANT!)you have to hold the battery check switch in the on position (as if checking the battery)while you wiggle the top cover off. If you look over the circuit board you'll see 2 holes beneath which lie the screwdriver slots for the pot adjustments. From this point, if you had a service manual and a VOM meter you'd undoubtedly be a giant leap ahead of me! Calibrating the meter involved a lot of trial-and-error, putting the top plate on and off (without screws but lining up the ISO wheels), and checking the reading against my Sekonic 308 at the middle and both ends of the MR4's sensitivity. Once I had the first one done I just calibrated the rest of them to it lining up the needle with the correct silver or black bar, didn't need to mess with the ISO wheels. When re-assembling the top cover, it's the reverse of taking it off (remember to hold the battery check on) except you have to make sure that the HI-LO switch in the meter and the one on the top plate are set to the same range or the cover won't go to place. And watch that HI-LO switch inside the meter, it likes to pop off its axis.

 

Honest to gosh, if Sherry only charges $38 to recalibrate it, I'd say DIY only if your time is worth as little as mine is (nowadays).

Ben,

Again great info!

Here is a link to a page I found describing how to take the meter apart, with illustrations. It's primary purpouse id to clean the window. It may be of interest to the people reading this thread.

http://feuerbacher.net/photo/frame.html?repair/Leicameter/Leicameter.html~Main

 

Cheers,

 

- Carl

Great! A little hard to see them but these are the pot adjusters, through those holes you can sort of see the screwdriver slots. One is behind a hole in the gear attached to the shutter dial, you have to rotate it so it lines up.<div></div>

I just bought one of these on ePrey, for about $100. It works, (can't tell how accurately yet) but has no manual. Would one of you gents be willing to photocopy your manual (assuming it isn't too lengthy) for $5 and send it to me? I really am rather lost after using only match needles and digital meters.

 

If this is a big copy job, just say so and I'll look for one to purchase.

Thanks,

Ray Hull

OCCULLUS-- It is a 24 page copying job for Kinko's, as I have no copying or scanning facilities.

 

Jerry

Oculus,

North West Collector Camera has one for $12 including shipping see

http://www.nwcollectorcamera.com/manuals/manualsl-m.htm You'll want item "LEI-028". I purchased an M4-P manual from him, very good experience.

Cheers,

- Carl

Excellent,thx.

 

Ray Hull