Minolta XG7 - Page 25

19
C. Description of circuit
The circuit of XG is explained in accordance with the block diagram.
1, Mode selector circuit
This is the general name for circuits which select the mode in accordance with the
switch operation or external signal (signal from strobo).
Auto mode: S,, S,. Sue A side Sg----ON
Manual
mode:
Sy,
S,,
Sige
M
side
S
geevees
ON
Bulb
mode:
Sa,
Sy.
Sipc**M
side
Sy---OFF
Exclusive strobo mode: .
On completion of strobo charge, the shutter speed control signal enters the control
circuit and the “60” LED blinking indication signal enters the indication circuit
respectively through the contact shoe.
Electronic SELF mode: S,:-----SELF side
2. Metering switch (Touch switch)
The switch (S,) operates when touch switch (S,,) and shutter button are lightly
pressed (about 0.5 mm).
Touch switch (S,,):
The periphery and the center of shutter button are electrodes. When it is touched,
the resistance between the electrodes decreases (co—>several M ohms).
This is electrically detected Tr;, Tr,, and then Tr, operate) and then power is
supplied to the metering circuit.
$s "
Metering
(Touch SW.) orrens
Tre
3. Voltage detecting circuit
If the power source voltage becomes lower than the specification during photography,
Tr turns off and the release circuit stops working. The basic construction is as shown
at left.
The B.C circuit is the same as this in principle of operation. It uses B.C indicating
LED instead of release circuit.
Sw.
Release
circuit
4. Metering operation circuit
This
circuit
converts
the
change
in
brightness
into
the
resistance
of
CdS,
adds
the
aperture
value
and
film
sensitivity
information,
performs
logarithmic
compression,
and
puts
out
the
signal
to
the
indication
circuit
and
memory
circuit.
,