Leicameter MR-4

[AllNoAll]

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On 8/3/2021 at 11:30 AM, andrew01 said:

You can also get adapters that do not reduce the voltage for a couple of £ on ebay, compared to the MR-9 voltage reducing adapter which is £25.  The former solution would be perfect if the meter has been adjusted to run on 1.55V.  

 

Example below.  Use with one SR44 battery:

https://www.ebay.co.uk/itm/283957488602?_trkparms=aid%3D1110018%26algo%3DHOMESPLICE.COMPLISTINGS%26ao%3D1%26asc%3D20200818142838%26meid%3D2661adcd3eff42618f80006764e36b81%26pid%3D101197%26rk%3D3%26rkt%3D12%26sd%3D203303537156%26itm%3D283957488602%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DItemStripV101HighAdFee%26brand%3DUnbranded&_trksid=p2047675.c101197.m1850&amdata=cksum%3A2839574886022661adcd3eff42618f80006764e36b81|enc%3AAQAGAAACAKPhsuSvp3Nk5tD6h5OSuSH%2F8Zpar8bUTSwzm3ahWmugdgwG2fdmhEXDNCNABYko8Uuv0pwK7ViTFsbi4A97RLJW3pYf4RcK6OJu8BI%2BXcMqW4pEAqx2haurfIybyIGWLdFiT7UlFVm5XuHSp1D3eRRGFOUtRInGHiqRfuu5YWkw1f1RmWS43FJF1PAIpbGHBMQFwiSXT2cZ%2FDxKpB%2BiY0lOf7smigKer1RX3I0phElSJtHRTyI0T3aTzOizcRbxQuPJ82dCu3Cj8u9JRk19ZrlqEnJON2CiNNorxagsi0Cp0RaqNxLH6s2SSJPnGPdCgKqq67YJByw3rEDXoI%2B3xQDdHnnZoIgDF26QrFPZkyybZjSDNDYC3nKQn3FO0xG2mfzOaopHsHqUaCtUmttNE%2Fbywn7mXmEAD3fI88LgmE%2BOpFVoRvfQv7jpQtEy7rxwNx2gnBlvGExVUjvu9W4mEUTuZXaaPZcWGvr7Y4lYt0aiPketXS9mkdeBXXbVvrgoTgH3po4UxG6mkhiPUsJJ3SKdL599THkBSLs1CosImGOlihBS5kDDU32Ux0xRKGkZx%2BHLgpWuJ98E9zS7XrJjciXi2bc%2FM6EwKDydyuL6Gtn7SuqlhAOoTiUndRFa5SSlTLqC2gpFpRSdT8RGpXCxIgxH8EfSQDwpuCAwLaEUjNQh|ampid%3APL_CLK|clp%3A2047675

Thank you for this. I will probably be getting this as the meter has been refurbished and converted to 1.55v

[Helge]

Am 3.8.2021 um 18:30 schrieb andrew01:

You can also get adapters that do not reduce the voltage for a couple of £ on ebay, compared to the MR-9 voltage reducing adapter which is £25.  The former solution would be perfect if the meter has been adjusted to run on 1.55V.  

 

Example below.  Use with one SR44 battery:

The turkish seller does „some“ calibration to 1.5V, so a calibration to 1.55V has to be requested probably. Since he demonstrates not really good knowledge about the difference between alkaline and mercury/silver cells regarding stability, I wouldn’t really rely in the accuracy over the whole magnitude of both meter ranges.

I would go for that adapter for silver cells linked here and buy a meter that is accurately adjusted to the original supply voltage.

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[AllNoAll]

11 minutes ago, Helge said:

The turkish seller does „some“ calibration to 1.5V, so a calibration to 1.55V has to be requested probably. Since he demonstrates not really good knowledge about the difference between alkaline and mercury/silver cells regarding stability, I wouldn’t really rely in the accuracy over the whole magnitude of both meter ranges.

I would go for that adapter for silver cells linked here and buy a meter that is accurately adjusted to the original supply voltage.

Well a bit late for that for me, as it shipped a bit ago. Their reviews are pretty good. I guess I will see.

[MikeMyers]

On 8/2/2021 at 4:32 PM, Michael Geschlecht said:

Hello AllNoAll,

The scratches on the top plates of "M" Leicas come about because the attachment shoe is improperly adjusted to that specific camera.

If you turn the meter upside down & look at the shoe: There are 3 screws with wide heads & 2 headless screws.

First: With the meter off the camera & in your hand: turn the meter dial to "B". Lift up the wheel GENTLY & continue turning to 30 Seconds (Yes), or, to where the wheel stops.

Set the CAMERA'S shutter speed dial to "B".

START to slide the meter into the camera shoe with you looking from the back to make sure that the meter bottom clears the camera top.

If it appears to being ABOUT to touch: Stop.

Pull out the meter.

Turn the meter upside down & look at the 5 screws described above in this Post.

With appropriate small screw drivers loosen the 3 large headed screws 1/4 or so of a turn. Loosen the 2 smaller screws until they do NOT protrude above the METER shoe on the camera side. Turn the 3 larger screws until they just stop LIGHTLY. Turn the 2 headless screws until they stop LIGHTLY.

Now slide the meter in until it is either: Clear of the top of the camera. Or else it HITS the camera top.

If the meter clears the camera top by about 2 millimeters: Snug the 2 headless screws alternately & incrementally. Not too tight.

Then little by little do the same with the 3 large headed screws checking that the meter is parallel to the camera top & continues to be appx 2mm away.

If, when you went to slide the meter in, in the beginning: The meter touched the top of the camera: Do what I just explained after turning the 2 headless screws a little so that they stick out between the meter shoe & the top of the camera. So that they lift the meter body above the meter shoe.

All of this is easier to do than it is for me to write.

I'll be back.

Best Regards,

Michael

Amazing timing - I just bought one of these meters from KEH.com earlier today, and I'll have it this coming Monday I think.  I noticed this thread, and decided to read it, only to find your instructional posts.  Gee, otherwise the meter would have arrived on Monday, and I would just slide it into place.  Now that I have found this information, I'll follow your guidelines/instructions.  Thanks again!

[jerzy]

Am 2.8.2021 um 21:37 schrieb AllNoAll:

Each meter is individually adjusted with the help of two trim pots on the circuit board and tested. 

impresive what the seller is writing, impressive, but bullsh....t. This is NOT the way how the lightmeter shall be calbrated for 1,5V. 
Electronical circuit has been designed having 1,35V in mind,  1,55v input voltage will increase the current flowing through the cell falsifying the measurent. By adjusting trim pots you may  correct measurement at one certain LV value but it will  not be correct for other values (ohms rule: U=I*R). Trim pots in MR are to compensate tolerancies in production of eletronical components, i.e. resistor with 1Kohm and tolerance of 2% may have between 980 and 1020 ohm and trim pots are for this reason. The correct way to convert any lightmeter device to 1,55V is to reduce the input voltage and this may be done in 2 ways: either use adapter with built-in voltage reduction, or modify the circuit by adding some passive component. I prefer the second way, it more reliable. Although you will need an adapter as well, but only for mechanical fit of an SR (LR)44 battery. 

[AndreasG]

Here is an excellent summary about background and possible solutions of the MR-4 battery problem:

http://www.buhla.de/Foto/batt-adapt-US.pdf

[Helge]

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vor 3 Stunden schrieb AndreasG:

Here is an excellent summary about background and possible solutions of the MR-4 battery problem:

http://www.buhla.de/Foto/batt-adapt-US.pdf

He‘s basically explaining in detail everything I did mention in my post:

either use a Shottky diode in series to a silver oxide cell (as a lot of the available real adapters do) or get a zinc air battery as a full replacement (with limited lifetime).

[MikeMyers]

What battery can I buy from Amazon, drop into an MR4, and expect it to work?  I understand it may not last as long as others, but I don't expect to use my M3 all that much to begin with.  

[Michael Geschlecht]

6 hours ago, jerzy said:

impresive what the seller is writing, impressive, but bullsh....t. This is NOT the way how the lightmeter shall be calbrated for 1,5V. 
Electronical circuit has been designed having 1,35V in mind,  1,55v input voltage will increase the current flowing through the cell falsifying the measurent. By adjusting trim pots you may  correct measurement at one certain LV value but it will  not be correct for other values (ohms rule: U=I*R). Trim pots in MR are to compensate tolerancies in production of eletronical components, i.e. resistor with 1Kohm and tolerance of 2% may have between 980 and 1020 ohm and trim pots are for this reason. The correct way to convert any lightmeter device to 1,55V is to reduce the input voltage and this may be done in 2 ways: either use adapter with built-in voltage reduction, or modify the circuit by adding some passive component. I prefer the second way, it more reliable. Although you will need an adapter as well, but only for mechanical fit of an SR (LR)44 battery. 

Hello Jerzy,

From the time when mercury batteries PX13 & PX625 were no longer available, up to & including today, my solution to the battery problem has been to take a 15mm HIGH QUALITY stainless steel split ring from a hardware store & pull 1 of the ends inward until it looks like the inside coil of a watch balance spring. So that the 15mm outside diameter fits in the place where the PX13/PX625 mercury batteries fit & the inside coil is tight enough to hold an SR44/357/303 battery tightly. Silver batteries are important for smooth & consistent readings.

Then, VERY IMPORTANT, the ISO number of the film/sensor in use that is set on the meter: MUST be raised +1/2 stop. That is then same as adding DIN +1.5 to the film/sensor speed.

Then the meter is simply used as it was before. Indicating exposures correctly. The resting point when activating the "Battery Test" button moves the needle a little further than the mark.

I have used this for years in an MR meter, a Metrastar meter & a Minolta 101. Often with slides. The readings all matched my next door neighbor's Minolta Flashmeter IV. 

What do you think? Would you try that?

Best Regards,

Michael

Edited August 8, 2021 by Michael Geschlecht

[Michael Geschlecht]

38 minutes ago, MikeMyers said:

What battery can I buy from Amazon, drop into an MR4, and expect it to work?  I understand it may not last as long as others, but I don't expect to use my M3 all that much to begin with.  

Hello Mike,

You can use a Wein, Zinc Air battery, 1.35 volt, as a direct "drop in" replacement for a PX13/PX625 without having to do, or change, anything. They read & act like their PX13/PX625 predecessors. They do not have as long of a usable life as some other types after the seal is opened for the battery to be put in the meter. 

Best Regards,

Michael

Edited August 8, 2021 by Michael Geschlecht

[MikeMyers]

THANK YOU!!!!

My meter should arrive later today.   This?   https://www.amazon.com/MRB400-Mercury-Replacement-Battery-Single/dp/B06Y3MGB6K/ref=sr_1_4?

dchild=1&keywords=Wein%2C+Zinc+Air+battery%2C+1.35+volt%2C&qid=1628436528&sr=8-4

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[AllNoAll]

7 hours ago, jerzy said:

impresive what the seller is writing, impressive, but bullsh....t. This is NOT the way how the lightmeter shall be calbrated for 1,5V. 
Electronical circuit has been designed having 1,35V in mind,  1,55v input voltage will increase the current flowing through the cell falsifying the measurent. By adjusting trim pots you may  correct measurement at one certain LV value but it will  not be correct for other values (ohms rule: U=I*R). Trim pots in MR are to compensate tolerancies in production of eletronical components, i.e. resistor with 1Kohm and tolerance of 2% may have between 980 and 1020 ohm and trim pots are for this reason. The correct way to convert any lightmeter device to 1,55V is to reduce the input voltage and this may be done in 2 ways: either use adapter with built-in voltage reduction, or modify the circuit by adding some passive component. I prefer the second way, it more reliable. Although you will need an adapter as well, but only for mechanical fit of an SR (LR)44 battery. 

Thanks for this! I’ll take your word for it. So will my readings be off then? Will the meter become defective?

Edited August 8, 2021 by AllNoAll

[Pyrogallol]

31 minutes ago, Michael Geschlecht said:

Hello Mike,

You can use a Wein, Zinc Air battery, 1.35 volt, as a direct "drop in" replacement for a PX13/PX625 without having to do, or change, anything. They read & act like their PX13/PX625 predecessors. They do not have as long of a usable life as some other types after the seal is opened for the battery to be put in the meter. 

Best Regards,

Michael

I tried a Wein Cell once in my Leica CL but it did not last long, by the next time I put a film in the camera it was dead.

[MikeMyers]

I guess I'd be better off buying a "blister pack", or maybe removing the battery when I'm not using the camera.

[AllNoAll]

26 minutes ago, MikeMyers said:

THANK YOU!!!!

My meter should arrive later today.   This?   https://www.amazon.com/MRB400-Mercury-Replacement-Battery-Single/dp/B06Y3MGB6K/ref=sr_1_4?

dchild=1&keywords=Wein%2C+Zinc+Air+battery%2C+1.35+volt%2C&qid=1628436528&sr=8-4

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Simply register for free here – We are always happy to welcome new members!

This is the battery they are referring to.

2 x WeinCell MRB625 Replacement Battery for PX625/PX13 https://www.amazon.com/dp/B07JCPG9YN/ref=cm_sw_r_cp_api_glt_fabc_V8F383RYEN96S49FD5CZ?_encoding=UTF8&psc=1

[analog-digital]

http://www.kantocamera.com/english/adapter/adapter_en.html

[a.noctilux]

1 hour ago, MikeMyers said:

I guess I'd be better off buying a "blister pack", or maybe removing the battery when I'm not using the camera.

Yes, blister pack is the way to go with zinc-air hearing aid batteries.

Removing zinc-air batteries needs to close also the "breath" ( air-hole ) with airtight tape.

Even then as the process of blending air to zinc oxide begins, the battery can have short life.

[Helge]

Covering the „breathe hole“ of an air zinc battery has some however small effect on the lifetime, the air is already in.

In any case don’t expect from an air zinc battery more than 6 months, may be 1 year.

[Michael Geschlecht]

2 hours ago, Pyrogallol said:

I tried a Wein Cell once in my Leica CL but it did not last long, by the next time I put a film in the camera it was dead.

Hello Pyrogallol,

Some people take the Zinc Air batteries out of the cameras/meters when they are not using them.

Some people say (I do NOT know this personally.) that putting a piece of masking tape (Comes off with minimal residue.) over the air holes in the batteries which have been removed from cameras/meters & then re-inserting them when the cameras/meters are used again: Extends the usable battery life somewhat.

Best Regards,

Michael

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Hallo,

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[MikeMyers]

5 hours ago, AllNoAll said:

2 x WeinCell MRB625 Replacement Battery for PX625/PX13 https://www.amazon.com/dp/B07JCPG9YN/ref=cm_sw_r_cp_api_glt_fabc_V8F383RYEN96S49FD5CZ?_encoding=UTF8&psc=1

Ordering now, it comes as a pack of two batteries.  If it lasts 6 months, that will be fine, ditto for a year.  The meter just arrived - now I need to read the instructions again before attaching it to my camera.  The batteries arrive Tuesday - I'll do all this then, and see how well I do over this coming week shooting B&W with my M3.  Thanks again - without you guys, I'd never have figured this stuff out!