CONNECTIONS TO THE LED
READOUT CIRCUIT
Even w ith the mirror cage removed,
you can't reach IC2; the driver for the
LEDs mounts to the other side of the flex
circuit. Fig. 48. However, you can make
most of the tests w ith o u t further
disassembly.
A t the A and M settings, IC2 considers
four values — the shutter-speed setting,
the film-speed setting, the diaphragm set
ting, and the light level. It then turns on
the appropriate LED to indicate the cor
responding shutter speed.
You can follow the connections in Fig.
52. The diaphragm information (AV) ap
pears at pin 10 of IC2. A t pin 12, IC2
receives the light-level (BV) and film-
speed (SV) information. The shutter-
speed information (TV) from the shutter-
speed resistor RTV goes to pin 11.
When you select the S mode, IC2 also
receives the minimum-aperture informa
tion at pin 9. Switch S12 at the fro n t of
the camera, Fig. 53, selects a resistance
value according to the minimum aperture
of the lens. W ith no lens installed, notice
that the S12 brush rests at the center of
the first resistance path, Fig. 53. Installing
the f/1 6 MD lens set to the smallest aper
ture moves the brush to the second re
sistance path — the resistor labeled R47
in Fig. 52.
The f/2 2 lens moves the brush to the
third resistance path; here, the S12 brush
connects pin 9 of IC2 directly to positive
battery, Fig. 52. W ith the f/3 2 lens, the
brush moves o ff the resistors to an open
portion of the board.
Notice in Fig. 52 that the part of the
mode selector labeled S8 connects the
minimum-aperture switch S12 to pin 9 at
the S setting. Then, w ith the release but
ton partially depressed, you should
measure a voltage at pin 9 — a voltage
which corresponds to the position of S12.
This voltage — the MD common volt
age — causes IC2 to indicate the proper
diaphragm opening fo r the light condi
tions. But, if you fail to set the smallest
aperture, IC2 only lights the overexposure
or underexposure LED in the S mode.
W hat if the IC fails to receive the MD
common voltage signal? You'll then find
that the LED readout w on't display the
diaphragm setting at the S mode. Although
you can't reach pin 9 of IC2, you can check
the MD common voltage at the top of the
camera; just measure the voltage to the
connection from the minimum-aperture
resistor shown in Fig. 54.
Set the mode selector to the S posi
tion, Fig. 55. Then partially depress the
release button and measure the MD com
mon voltage. W ith o u t a lens, you should
measure around 1.4V. Minolta specifies
Figure 55
M O C O M M O N VOLTAGE
FLEX STRIP
Figure 53
Figure 54
