Final update on Nikon Photomic FTn CLA

Now I am officially finished. I installed 2x BAT41 Schottkly Diodes in the lower unit of the meter. This in theory will drop the voltage down to usable levels for the meter. After installing I tested the voltages and they are just +/- 1.5mv depending on where one takes the measurement.

 

Here is an out of focus (handheld) image of the installed diodes.

 

 

The diodes are in the white heat-shrink tube. They are placed in series and the cathode of the lead diode is connected to the brown wire from the battery compartment. Installation was a little harder than I expected because the solder is so old. Took some patience to heat it up to melting point.

 

So this is a wrap. Next project is another FTn that I purchase as parts/repair. The battery test works on this new FTn but it does not have any activity other that the test. New challenge. Should be fun.

so you did get that stuborn last screw out. nice job.

Yes I did. Took using a set of precision screwdriver that look to be JIS compliant. Plus some more Isopropyl Alcohol. Thanks

when doing work on that scale, tools do make a difference.

That'S great Brian.. I wish I could look back on my projects and say... it'S a wrap!! IF this is your idea of fun... well looks like you've got your fun just waiting for you on the the Ftn.... Have a blast and let us know how it works out!!

Did you measure the metering error before modification? How far out was it with standard 1.5 volt cells?

I did make voltage measurements before and after. Before levels were 3.15vdc with the switch on and measuring across the battery wires. After installing the diodes I measured 2.9vdc at the same location. This is without a load on the meter, meaning no light. With the diodes in, I can now adjust the Meter Sensitivity pot on a known shutter speed, aperture, and ASA (I love using that instead of ISO - LOL).

 

As for the other FTn, I took it apart and immediately found the CDS Sensitivity Pot was maxed out. I put the wiper where it should be (SWAG based on where the wiper is on the other FTn) and am now getting light readings. Still need to do a few other things but I think I can get this FTn working. Whoot! The luck of the Irish is with me. LOL

It's been a long time since I did mine, but my recollection is that with alkaline batteries readings were approximately two stops off before adjusting and maybe a little more with silver oxide. One could compensate simply by offsetting the ASA, but the battery check is not much use, so you have to monitor battery condition, especially if using alkalines.

Matthew, again you are correct in the ASA compensation. But not everyone will think like that. It is obvious that you are an old school photographer who is always thinking about the three settings for a correct exposure. I asked some younger digital shooter about that one day and they kind of stared at me. Hmmm... (not so say all young digital shooters do not know).

 

[uSER=2403817]@rodeo_joe|1[/uSER], I retook some measurements before applying the leatherette. The no-load voltage is 2.95vdc at the battery terminals (S625PX Silver Oxide batteries). When the battery is on and there is a load (this is the entire metering circuit), the voltage is about 2,47vdc. This is to be expected. This morning I double checked against a Luna Pro SBC meter and confirmed that the meters match. (My LP-SBC, Minolta IV F, and my F2AS all match for light readings).