[Milsurplus] Vibrator failure

[aGEnuine Ham]

John:

One reason the "ACC." position* was developed for automobile ignition
switches was vibrator failure during the voltage dip when the starter is
engaged.  It also reduces the battery load during cranking, and that is
an understandable explanation to a mechanic, so it is the one usually
given.  You see, the vibrator does not have enough drive voltage to the
reed, and the back contacts weld together, leading to the destruction of
the vibrator, and the transformer if the fuse is too large.  It also lets
the smell out of the radio.

Now for the milsurplus content.  I had a cousin who was a paratrooper in
Korea, and he once told me that they had a radio in their Jeeps which
experienced this problem with vibrator contacts sticking when the radio
was left turned on during starter engagement, and there was a field mod
which came out to overcome the problem.  I do not remember the specific
circuit, but I do recall it seemed overly complicated to me.  This ring a
bell with anyone?

*The power is removed from the accessory connection when the starter is
engaged, and only the ignition (and fuel pump etc. these days) is left
connected during starting.  Some of the automobile trade school texts
from the 40s and 50s explain this a lot clearer than I can.

73,
George
W5VPQ

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