Thursday, April 18, 2013


Besides a dead battery, there are a few things that could be affecting the needle movement / lightmeter operation...

1) The needle itself is 'stuck' to one side. This is typical after 50+ years of dirt and grime. The needle can 'stick" to the small, tubular, white colored,  plastic stop(s) on either side the galvanometer. Next time it happens, try rotating the ASA dial all the way in one direction and then the other, and finally back to your normal ASA setting. If the needle was stuck, this will usually dislodge it. The permanent cure is to remove the eyepiece diopter, and very, very carefully, clean the sides of the needle with a small swab soaked in alcohol. If you can see a 'fuzzy edge' on either side of the needle; the needle needs cleaning.

2) Some 'home-made' reflex battery adapters are built from a "stack of washers" or similar. The contact points between the washers can corrode or otherwise not make electrical contact. This causes an interruption in the battery circuit and the needle won't function. Loosening and re-tightening the battery cover may fix the problem temporarily. One of our customers even uses a wad of aluminum foil wrapped with tape as an adapter.

3) The 'U' shaped spring at the bottom of the battery may be permanently flattened. This can happen if the 'home-made' adapter length is too long. Sometimes the spring is broken in half at the bend section, and the new adapter is made to take up the difference in length. There will not be any tension from the spring so contact will depend on the battery cover being screw down tightly. If it is screwed down too tight, the spring holder (plug) itself will be pushed away from the cameras body. This in turn will prevent the ground ring from making a good ground connection with the camera body and the circuit may be interrupted.

4) Corrosion on the connections inside the camera located on the backside of the plug can cause an intermittent open. There are (2) wires. One connected to the grounding ring and 1 is connected (soldered) to the rivet holding the spring to the plug. If there is enough corrosion, the wires can have intermittent/bad contact. The fix is to replace the wires and/or the plug. Unfortunately, one of the wire going into the shutter is a "Litz wire". Litz wire is a woven strand type of wire. 

The weaving of the strands acts like a 'sponge" and leaking mercury can 'wick' its way all along the wire. As this happens, the wire corrodes and disintegrates. Typically up to the furthest point inside the shutter housing. Repair requires complete disassembly of the shutter housing and replacement of the Litz wire.

5) There is corrosion on the ground ring that is in between the plug and the camera body. The corrosion is caused typically, by a mercury battery being left in the camera too long and subsequently leaking creating a greenish-whitish powder-like coating. 

     BONUS! The ring is nickel plated steel and the camera body where is grounds is
     aluminum. Two dissimilar metals will most always promote corrosion.

This corrosion can be 1) on the threads of the cap and body or, 2) on or near the spring in the battery well. Sometimes the corrosion is superficial and while present, doesn't cause any problems. If corrosion is present, the battery contacts and related parts should be cleaned thoroughly. You can swab the battery well with plain vinegar, which is 5% acetic acid, and the acid will neutralize and dissolve the corrosion. Swap again with alcohol to remove any trace of the acid.
If, when installing a BolexRepair battery replacement kit, you notice that the battery well spring in your camera is damaged, bent, missing, corroded, etc, we can replace the plug/spring and/or make a custom length adapter to specification. The normal gap length at the tip of the spring should be about 1/8".  

If the spring is bend down slightly (less than 1/8" gap), don't pull it up! This may cause the spring to crack or break. Best thing to do here is to insert a small piece (1/8" thick or so) foam rubber between the spring back and the black plastic spring holder. This will add a small amount of pressure to the back side of the spring. Be sure not to add to much. Just enough to cause the spring to move away from the bottom of the battery well.

If the tip of the spring is nearly closed, or is smashed flat, the adapter probably will not work. There is only about .025-.040" of compression of the spring necessary when the battery cap is fully seated. Machined aluminum adapters, as supplied with our kit, take up the exact length required for use with the thinner PR44 or 675 battery. Our adapter does not allow for damaged springs. Please contact us for an estimate to repair the battery well spring and/or rewire the lightmeter circuit

For more information on the lightmeter battery adapter kit:

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