Repair manual

oscilloscope pictures shown in sections 24.100 – I. The
camera shutter normally blocks the light from the photocell,
and oscilloscope spot moves over the same line until the
shutter is released and starts to pass light to the photocell
at “A”. As the shutter moves very rapidly, the spot rises
almost perpendicularly until the shutter is fully opened, “D”.
As long as the shutter stays fully opened, the spot will
travel horizontally to the right of “D”, but in a shutter
opening of 1/50 second it will get only to “E” before the
shutter starts to close. The period during which the shutter
is closing is depicted by the line from “E” to “F” as the full
brightness fades to total darkness at “F” and stops there,
permitting the spot to continue over across the bottom of the
screen.
D E
A F
When oscilloscope is adjusted properly, the trace will
“Trigger” only when shutter is released or flash circuit
closes’
As previously stated, the current through the shutter switch
contacts also controls the vertical motion of the spot. This
is done by a circuit using the same electrical characteristics
as a flash bulb in a flash gun, and is arranged to give a
conspicuous vertical spike at the instant the contact is
closed or opened. For example, if a camera with a properly
adjusted switch is attached to the flash connection, and the
release button operated without a light beam, the oscilloscope
spike will look thus when the button is pressed and the switch
closed:
And thus when the button is released and the switch opened:
This downward spie has no significance in out shutter testing,