Why do the Nikon F and F2 meters fail?

First- When batteries are left in the meter over long periods of time corrosion will occur. However, the effects of the corrosion are not easily seen in the battery compartment. The corrosion effects the main power wire that leads from the battery compartment to the rest of the circuit. This corrosion is only evident from the inside of the meter.

Second- The switch in the photomic, T and Tn are all about the same. Spring loaded contacts that loose their spring in time resulting in a open circuit. The Ftn meter switch is a little different because it has both the ON/OFF and battery test in the same switch. All of these switches can and do cause the meters to fail.

These first two causes are likely suspects if the meter is completely dead. The next two causes will only make the meter erratic and inaccurate.

Third- The photomic meter has one large Cds cell in the front window. All of the other meters have two smaller Cds cells connected in parallel. The resistive properties of the Cds cells change with time. Which means that if the meter was accurate in 1969 then there is a good chance that it is not accurate in 1999. Good Cds cells will have a resistance between around 100 ohms in bright light to 1 Meg ohms in a dark room. However, most of the Cds cells that I have seen in these meters only range from 100 ohms (light) to 10 k ohms (dark). This causes the meter to be inaccurate.

Forth- Another thing that will cause these meter to be erratic is the ring resistor. This resistor changes its resistance according to the shutter speed and f-stop set on the camera body. It is a carbon strip that is glued to the inside of a metal ring. There are two spring loaded contacts that ride along the strip which provide the two ends of the resistor. The carbon stip can get dirty and produces a wildly fluctuating resistance. This in turn causes the needle to fluctuate wildly as well. A gentle cleaning of the resistor with cotton swabs and isopropyl alcohol will clean the resistor. However, after the resistor is clean, it does necessarily have the same resistive properties that it did when it was new. So the resistance must be measured at each F-stop and shutter speed to know how it behaves.

Nikon used a the same type of ring resistor in the photomic, T, and Tn meters. Then they changed the ring resistor in the Ftn to accommodate the semi- auto indexing. The DP-1 and DP-2 have another type of ring resistor which can come apart into two separate rings. The ring resistor of the DP-11 is the best kind of ring resistor because of its better design. It looks just like the DP-1 ring but it has a gold colored strip instead of black. Instead of a continuous strip of carbon that the two contacts rubbed against, The ring resistor of the DP-11 uses the fact that resistors that are connected in series will add mathematically. The continuous strip of carbon is cut up along its length with taller pieces of metal between them. It is similar to a series of mountains and valleys where the mountains are the metal pieces and the valleys are the carbon resistive material. This design allows the two metal contacts to run along the top of the "mountains" and not rub against the softer carbon deposits "valleys". Therefore, the ring resistor of the DP-11 will last much longer than the ring resistors that Nikon used in their earlier meters.

Fifth- Another problem with these meters is the needle assembly. With time, the needle wears out and begins to stick. It may also loose its electrical conductance in the coil of wire which causes the needle to be stationary regardless of how much voltage is placed across it. Since these needles are very small and delicate, they are extremely difficult to repair and the best option is to replace a bad needle. The photomic, T and Tn all have similar needle assemblies which had a little open window to adjust the needle through. However, these needles are more prone to failure. With the introduction of the Ftn meter, Nikon used a sealed needle assembly which does not fail nearly as often as the earlier ones. Nikon continued to use sealed needle assemblies in the DP-1 and DP-11 meters.

These are the main reasons that cause the Nikon photomic meters to fail. As stated above, these 5 causes do not have anything to do with poor engineering, but are just due to the nature of the electronic devices available at the time the meters were produced.

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