TM 11-6720-239-35
Figure 1-6. Finder assembly, optical schematic diagram.
charge through timing switch S2, and the shutter
and it will pass more current. When the selected
circuits are ready for another exposure.
capacitors are fully charged, the excess current is
b. Shutter Flash Circuit. Operation of the shut-
diverted through resistors R6 and R2 to the base
ter flash circuit is controlled by flash switches S3
of transistor Q1. When the current at the base of
and S4. When the shutter is uncocked, flash
Q1 builds up to a high enough level, Q1 is trig-
gered. Current now flows from the battery,
switch S4 is held closed by the make pin on the
opening blade and flash switch S3 is held open. As
through battery switch S1, variable resistor R1,
the shutter is cocked, flash switch S4 is released,
the collector and emitter of Q1, and potentiometer
and opens. The break pin on the closing blade
R3 to the negative side of the battery. Since the
forces flash switch S3 to close. When the shutter
collector of transistor Q1 and the base of transis-
is tripped, the opening blade slides forward, and
tor Q2 are connected (at the junction of resistor
the make pin strikes flash switch S4, forcing it to
R1), Q1 draws the base current of Q2. When the
close. Flash switch S3 is held closed by the break
current at the base of Q2 has been sufficiently
pin on the closing blade which is in the grip of the
reduced, Q2 is cut off. The magnet hold circuit is
electromagnet. Thus the flash circuit is completed
now broken, and electromagnet L1 is deenergized.
and will cause an attached flashgun (c below) to
The closing blade is released, and snaps closed.
fire. When the closing blade is released by the
The light exposing the negative is cut off, and a
picture has been taken. When the pressure on the
electromagnet, flash switch S3 opens, and breaks
the flash circuit. Since the flash circuit is only
shutter release button is removed, battery switch
closed while the film is being exposed, there is no
S1 opens, and all current is removed from the
circuit. When the shutter is re-cocked, timing
danger of an accidental firing of the flashgun.
When a flashgun is plugged into the shutter, flash
switch S2 is closed. The timing capacitors dis-