Re: SRSG timing light

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

All,

The TV field scanning frequency is just under 60Hz, at 59.94Hz.
It used to be exactly 60Hz in the old days of black and white TV. 
They changed the frequency when they added color because
they needed a submultiple of the color subcarrier frequency to
permit the color subcarrier frequency to better fit into the 
relatively "unused" frequency areas between the harmonics in
the signal.  Because of all this, if a rotary sync gap is observed
by TV picture light, the gap rotor pattern will appear to slowly
rotate and will make a full rotation in about 16.6 seconds.
(*correction, see my test below)
Since the TV freq is slower than the AC freq, the pattern will
rotate in the same direction as the motor rotation.

So the answer is yes, a TV can be used to tell if a motor is
locked, but you must take into account that the pattern will
make a full rotation in 16.6 seconds in the direction of motor
rotation.  (*correction, see my test below).

*I got curious and did a test.  I just ran my sync gap in a dark
room with the TV on, and the pattern rotated 1/4 of a turn in
just about 8.3 seconds, which would be about 33.2 seconds
for a full rotation.  So the pattern actually rotates twice as
fast as I calced above.   Maybe it's
because the TV frame RATE of 59.94 divided by 2, or 29.97Hz,
is dominating the situation, and making the pattern appear
to rotate twice as fast as expected from the faster FIELD rate. 
In any case, this test shows that the pattern will actually rotate
one turn in 33.2 seconds when the motor is sync-locked, and
observed with a TV as a stobe source.  The 33.2 seconds for
one rotation may cause confusion and inaccuracy in determining
if the motor is locked, so it's probably a lot better to use a 
fluorescent light.

The pattern was kind of hard to see anyway.  It is much
much easier to see the pattern by using a fluorescent light,
and of course the pattern is rock-steady under fluorescent light.

John Freau