Minolta XD - Page 21

4) When S; is turned OFF, the following circuit operations are performed.
@7T i operates and power supply to camera continues even with finger off shutter button,
and LED in finder goes out.
@T.2 operates to supply power to shutter magnet (M3) in shutter block.
® Voltage is applied to the base of Ti3 and preparation is made for the operation of
diaphragm magnet (Mz) by exposure control circuit output k.
The exposure control operation is explained in the following.
{0 Operation in S mode
(Diaphragm control switch S,, is at S)
® Exposure control] circuit compares shutter speed information h with stop-down metering
information g (SPC metering information and film speed information in stop-down) and
sends the output k to diaphragm magnet in the form of signal.
@ When LED in finder before camera operation is F 5.6 for instance, h<g before preset
operation and diaphragm magnet is kept attracted and preset lever is operated to stop
down.
@ Just before F 5.6, h=g, and signal is given to diaphragm magnet by output k to turn on
magnet M2. Then magnetic piece lever, held by permanent magnet, is operated to stop
preset lever and to stop lens side aperture at F 5.6.
© When over-range (A) is lighted, h<g before present operation and still h<g even
when aperture is minimum (F16). Therefore, no signal is given to diaphragm magnet,
and preset lever operates over full stroke.
® When under-range (VY) is lighted, h=g before preset operation. So, signal is given
to diaphragm magnet by output k when S; is turned ON, thus stopping preset lever
to keep lens side aperture fully open.
@ When shutter speed dial is set at X, B, O, information h is nearly earthed, and its
relation with stop-down metering information g is always h<g, and the aperture on lens
side is the value set at that time.
© When exclusive strobo is mounted and completely charged, information h is nearly earthed
by signal p irrespective of shutter speed dial position. And always h<g, and the aper-
ture on lens side is the value set at that time.
[2] Operation in A mode
(Diaphragm control switch S,, is at M, A.)
@ Irrespective of shutter speed dial position ranging from 1 to 1/1000, input h to exposure
control circuit is nearly set at 1V because Sy, is at M or A.
@ Even when the exposure of this camera is minimum, stop-down metering information g is
over 1V. Therefore, h<g, and no signal is sent to diaphragm magnet the same as in the
abovementioned over-range (4) indication. Then, preset lever operates over full stroke,
and the aperture on lens side is the value set at that time.
@ When shutter speed dial is set at X, B, O, and when exclusive strobo is used, the opera-
tions are the same as in S mode.
5) On completion of exposure control and releasing of mirror, memory switch S¢. is turned
OFF.
When in A or S mode, the scene brightness, passed through the aperture, is measured by
SPC and stored in condenser C2. When in M mode, only shutter speed setting informat-
ion is stored in condenser C2.
6) When mirror raising is completed, shutter is released and trigger switch S, is turned
OFF by the function of timing cam for exposure control on shutter side.
7) When S, is turned OFF, transistor switch Qs: is turned OFF via counter circuit and
Qs turned ON. Then shutter time is counted by the expansion collector current of
transistor Q,; and counting condenser, and the result is transmitted to speed control
circuit.