military: TV-7 U; Fuse bulb & pilot lamp

I have a TV7/U,it use a bulb as a fuse.It is important to use the correct type: 81,(6,5V,1,02A;6,6W).

I have found that types 81 & 47 (pilot lamp) bulbs are used in Gottlieb flippers, so it is easy to buy them at sellers  of flippers spares parts  (in France there is one on Ebay.fr,he sell box of 10  at very reasonnable price)

On the picture,the; yellow bulb is original (GE81),he silver one is a 81 for flipper (exactly similar to original).

I have tested the spares,they runs as originals ones.Using european cars 6V bulbs is also a solution,but they do not complies exactly (6V; 5W ),flippers spares are preferables.

Olivier Palix

• Spares bulbs: GE81,81 for flipper (98 KB)

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Actually 6V car bulbs are really 7V and 12V car bulbs are really 14V. This is because the 12V car battery is over 14V on charge and traditionally was a nominal 13.8V. Car bulbs (lamps) also must give reasonable life. In contrast a 6V dry battery lamp may have a 4.8V lamp and be rated only 500 hours or much less (so as to be more efficient). The almost orange shade pilot bulbs are longest life and thus lowest efficiency, some may be 5,000 hours. As a rule of thumb, increase of 10% Volts is 1/2 life, or a 10% decrease might double life, very white filaments are short life and more orange filaments are long life.

The 6.3V of indirect valve filaments is derived from 6V lead Acid battery applications in 1930s, including early car radio sets. Modern low maintenance or "calcium" technology 12V batteries are closer to a nominal 14.2V than 13.8V when charged but on load (i.e. in a car with engine running).

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