Minolta XD-11 Repair Manual page 7

Figure 15
Figure 16
Figure 17
BLACK PURPLE
W HITE TO S7
The components for the diaphragm-
control circuit also mount to the circuit
board at the bottom of the camera, Fig. 15.
But you can't as yet see switch S7. Switch
S7 is part of the mirror-release-magnet
assembly M1. As the armature of M1 jumps
VIOLET
away from the core to release the mirror, it
opens S7. Notice in Fig. 14 that S7 must be
BROWN
TO M2
open in order for transistor T13 to conduct.
In effect, opening S7 turns on the
BLUE
diaphragm-control circuit. A t the same
time, S7 provides power for the shutter
electromagnet (the electromagnet that
holds open the closing blade fo r the
length of the exposure). Opening S7 also
switches off the LED display.
A problem w ith S7, then, could cause
quite a few problems. Although you can't
as yet reach S7, you can check its opera­
tion. Locate the w hite wire attached to
the lower circuit board, Fig. 15. Measure
the voltage between the white wire and
ground; you should measure 0 volt, in­
dicating that S7 is closed.
W ith S7 open, you should measure
around 1.3V at the white wire. But how
can you open S7 to measure the voltage?
One way is to hold open the shutter at the
bulb setting. Then push the M1 armature.
Fig. 16, away from the M1 core (toward
the fro n t of the camera). The M1 ar­
mature now opens switch S7. Conse­
quently, you should measure around 1,3V
at the white-wire connection, Fig. 15.
The technique for holding open switch
S7 also allows you to conveniently check
the coil of M2 and capacitor C5, Fig. 14.
Consider that the diaphragm-control cir­
cuit fails to latch the diaphragm-closing
lever; the diaphragm-closing lever always
moves its full distance in the " S " mode.
You might first check for the charge
across the diaphragm-control capacitor
C5. Measure the voltage between ground
and the positive C5 lead. Fig. 15; you
should measure -t-3V.
If you're getting the full battery voltage
across C5; the problem could be w ith T5,
T13, or the coil of M2. Another possibility
is that T13 isn't getting the turn-on signal
from the aperture-control comparator.
But you can quickly check the transistors
and the M2 coil w ith shorting tests.
There are a couple of ways you can
check to see if M2 repels its armature
when C5 discharges. Try setting the mode
selector to the " S " position. Then watch
the diaphragm-closing lever, Fig. 5, as you
release the shutter. If there's a problem in
th e
diaphragm-closing lever always travels its
full stroke.
Now short between the emitter and
collector of transistor T5, Fig. 15, as you
release the
closing lever should stop after traveling a
d ia p h ra g m -co n tro l c irc u it,
shutter. The diaphragm-
the