Help! No one can fix my Leica M6 TTL light meter (not even Leica)

[pedaes]

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10 hours ago, wlaidlaw said:

has got round to it yet.

Can't see that happening any time soon. Equally. can't see high demand for the service.

I think Will and Cathy's big advantage is their timescale for the work done, as well as the quality of the work. 

[wlaidlaw]

43 minutes ago, pedaes said:

Can't see that happening any time soon. Equally. can't see high demand for the service.

I think there would be a fair demand from folks with the older drip coated (very soft coating) Leica lenses plus pre-war uncoated lenses. My father had a habit of cleaning the front of his coated (by Oude Delft in 1948) Summar with his tie. By the time I got round to taking the IIIa and Summar to Wallace Heaton for him in 1965, there was only a very thin rim of coating left round the edge of the front element. Whoever Wallace Heaton used, did a lovely job, repolishing the front element and then hard coating it. 

Wilson

Edited January 3, 2021 by wlaidlaw

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[Matlock]

Wallace Heaton, that's a blast from the past. 

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[pedaes]

14 minutes ago, Matlock said:

Wallace Heaton, that's a blast from the past

Indeed! Still have a 68/69 Blue Book that is a interesting browse. In that year they were selling M3, M2 and new M4, as well as Leicaflex of course. The latter being their most expensive camera.

Edited January 3, 2021 by pedaes

[wlaidlaw]

This is the Wallace Heaton receipt for my currently owned IIIa and Summar from 1937. I bought it from the daughter of the original owner. WH was bought by Dixons in the 1970's and vanished a few years later. 

Wilson

 

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[pedaes]

2 hours ago, wlaidlaw said:

This is the Wallace Heaton receipt for my currently owned IIIa and Summar from 1937. I bought it from the daughter of the original owner. WH was bought by Dixons in the 1970's and vanished a few years later. 

Wilson

 

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Fabulous! I would love to know who the original owners were of my 30's cameras.

The photo's of the WH store managers at the front of the Blue Book is also a real step back in time. 

 

[Danner]

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Data point:  My M6 was serialized on May 8, 1986, in the third batch of M6 classics ever assembled by Leica, and it's meter still works flawlessly.

I do hope I haven't cursed it by making this statement.

[Peter_308]

Having read this thread with interest, I wonder if anyone has had a similar experience to me.

I have 2 M6TTL’s, a 0.85 and 0.58. Both were bought second hand over the last 4 years. The 0.85 was CLA’d not long after I purchased it by Aperture UK as the VF frameline selector was sticking. I have not had the .58 CLA’d as it was MIB.

The lightmeter on both cameras works fine but give consistently different readings. Testing to other cameras and a handheld meter the 0.85 meter is spot on. However, the 0.58 is a good 1.5 stops under exposed. I wonder if this is a sign of a poor circuit board that’s going to go “pop” in the not to distant future, or is the meter just not calibrated properly (from factory?) and this is something that could be adjusted as part of a CLA.

Any thoughts greatly received. 

[Pyrogallol]

If the meter on the 0.58 camera is consistent in its reading, adjust the ISO to correct the exposure so that it matches the other camera. If it is always 1.5 stops underexposed reduce the ISO by 1.5 stops, ie for a 400 ISO film set it to around 150.

I assume you have tried a new battery first?

[Peter_308]

Yep, fresh batteries always and I use the ISO comp method to deal with the issue. However, the OCD in me wants an accurate meter and I do worry that this is a sign that my meter is going to fail.

[a.noctilux]

Hello Peter,

just curious,

and if ...

had you swapped the back doors of your two M6 TTL ?

[Peter_308]

I haven’t swapped the back doors on either body but that’s not to say a previous owner hasn’t done so. Or are you saying swap them over and see if the under exposure moves too?

BTW, I have rotated the ISO dial in both cameras back and forth to make sure contacts are as ‘clean’ as possible. 

[a.noctilux]

Yes to see if the problem moves with the back door.

 

[wlaidlaw]

Are you using silver oxide batteries? These give more stable voltage than either alkaline or lithium batteries do. The M7 has a Schottky diode regulator, so a pair of 1/3 DN lithium are fine in it rather than 4 x SR44 but I am not sure if the M6/M6TTL have a regulated PSU or not. My guess otherwise would be a dry solder joint on the battery compartment. Batteries do exude some corrosive vapour and these can corroded the solder joints. Contax SLR's were notorious for this fault. 

Wilson

[Peter_308]

Wilson, I’m using 2 x fresh SR batteries but will try a 1/3 DN. I’m also going to swap the back doors as a. Noctilux suggested.

Thanks for the ideas and I’ll report back.

 

[plasticman]

There are companies that reproduce circuit boards. I'm guessing the cost for doing so is only acceptable if enough boards need to be produced. So if the scale of this problem begins to warrant it, this could be a KickStarter-type project, I imagine.

This is totally outside my area of expertise, so please correct me if I'm wrong - for instance, if these circuit boards have some elements that are impossible to reproduce?

[Peter_308]

On 1/24/2021 at 1:41 PM, Peter_308 said:

Wilson, I’m using 2 x fresh SR batteries but will try a 1/3 DN. I’m also going to swap the back doors as a. Noctilux suggested.

Thanks for the ideas and I’ll report back.

 

Well, swapping back doors made no difference - even cleaned the gold contact points on both doors and the camera bodies. Also tried various different batteries but to no avail. The 0.58 is consistently 2 stops under exposed compared to my accurate 0.85. 

My understanding from an earlier post on this tread is that meter calibration could only be carried out by Leica with specialist equipment. Anyone know how true this is and whether they are still able to calibrate - assuming this is a different solution to repairing or replacing the circuit board that no longer is available?

[wlaidlaw]

17 minutes ago, Peter_308 said:

Well, swapping back doors made no difference - even cleaned the gold contact points on both doors and the camera bodies. Also tried various different batteries but to no avail. The 0.58 is consistently 2 stops under exposed compared to my accurate 0.85. 

My understanding from an earlier post on this tread is that meter calibration could only be carried out by Leica with specialist equipment. Anyone know how true this is and whether they are still able to calibrate - assuming this is a different solution to repairing or replacing the circuit board that no longer is available?

My thinking would be to send it to Will van Manen in the Netherlands, who is I understand, more flexible on what he will/can repair than Leica are. Leica usually do a CLA which is a minimum of €800 + Tax for a film Leica, before they start charging for work on anything else. From my experience with Will, his charges are based on the work he actually has to do and less formulaic. If in the USA I would send it to Don Goldberg. 

Wilson

[Peter_308]

2 minutes ago, wlaidlaw said:

My thinking would be to send it to Will van Manen in the Netherlands, who is I understand, more flexible on what he will/can repair than Leica are. Leica usually do a CLA which is a minimum of €800 + Tax for a film Leica, before they start charging for work on anything else. From my experience with Will, his charges are based on the work he actually has to do and less formulaic. If in the USA I would send it to Don Goldberg. 

Wilson

Thanks for the suggestion Wilson, I’ll contact Will.

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[adan]

A couple of thoughts:

1) the M6TTL has fairly complex circuitry. At least two "circuit boards," each with a number of "chips" or integrated circuits on them.

One flexible CB wraps over the camera from the battery well on the front all the way to the ISO contacts that connect to the ISO dial on the back. Passing the shutter dial on the way, where it detects the shutter speed dial position. Another is across the top of the rangefinder, and likely contains the "drivers" for the viewfinder LEDs and the flash-quench (among other things). It has quite a large chip (probably a RISC processor). The top CB is why the TTL had to be 3 mm taller than the classic M6.

There is a picture here of a partly-disassembled M6TTL that shows both CBs in position (the extra part on the table is - I believe - a much simpler M6 Classic CB).

https://www.photo.net/discuss/threads/help-m6ttl-and-problem-with-exposure-dot-and-arrows.430897/

Of note, one can see the fine twisted black+white wires leading out of the front board to the two metering cells (one for ambient light, top, the other for flash metering, bottom)

I suspect the dedicated integrated circuits are likely the hardest part to source if they fail. Once the chip factory throws away the "blueprints," they have to be re-engineered from scratch. Not cheap, in a small run. Possibly more per chip than the value of a used M6TTL at this point.

2) However, I would also expect that the meter calibration is done by a variable resistor (or potentiometer, or "pot," or "trim-pot") - a device in the circuit with a tiny knob or screwhead that can be turned back and forth with a jeweler's screwdriver to change the flow of electrons. Something that can easily be done in the factory during manufacture (and later, if needed) without needing a degree in EE.

There is a "pot" visible on the vanilla M6 board (coppery "doughnut" in the center) - but that is the one driven by the shutter dial, as an analog computer (current passed is proportional to exposure time). There should be another (may look quite different) somewhere for meter calibration.

Provided the CBs and the parts on them are working, the "pot" can be tweaked pretty easily with minor disassembly (as in the photo, pull the core of the camera out of the metal/leatherette casing).

Edited January 27, 2021 by adan