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Battery Check

Turning the Mode Switch to "Battery Check" sets

IC-101 to the check condition. IC-101 directs IC-102 to
drive the Piezo Buzzer through pin 25 and the Timer
LED through pin 41. The display is also involved:

1. When voltage is above 2.75v, the tone is steady

and the LCD and LED are steady,

2. When voltage is between 2.65v and 2.75v, the

tone, LED, and LCD are intermittent.

3. Below 2.65v there is no indication.

4. Below 1.9v there is a constant warning tone.

Remember also, when voltage is below 2.65v, release is

inhibited but will reset by itself when new batteries are
installed.

Winder Dedication

There are five winder or motor drive dedication

contacts on the camera's bottom. From front to back
they connect as follows:

1. SF Switch located near the battery case. The

switch is closed, shorting the contact to chassis when

there is no film on the spool,

2. RK Switch which closes, shorting the contact to
chassis when the rewind button is pressed,

3. & 4, MD Switch located near the contacts.
With the mirror down, the contacts are shorted
together. With the mirror up, #3 is open and #4 is
shorted to chassis,

5. U Switch located on bottom rewind side. The
switch closes, shorting the contact to chassis when

film door is open.

Self-Timer

Closing the Timer Switch (SW-104) connects pins 20

and 26, IC-101. This programs an electronic delay
between the time SW-101 closes (mirror rises) and

when IC-102 signals MG-1 to release the opening
curtain. The timer interval is 12 seconds with flashing
LED and buzzer to call plenty of attention to the
situation.

II. EXTERNAL TESTS

1. Try operating the camera in mechanical mode, "B"

and "60." There should be normal shutter and

transport function. If not, remove the bottom cover,
then check the shutter charge gears, mirror charging
lever, and release lever.

1 Move the Mode Switch to "Battery Check." There
should be audible and visual (LED) indications. If not,
test battery voltage. Below 2.65v the LED and Buzzer will
not function. If the voltage is above 2.65v

there may be a

power circuit problem or possibly a dirty battery contact.

3. Set the Mode Switch to "Auto," the shutter speed

control ring to 1/125, then press the release button one-
half stroke. The LCD in the viewfinder should show a bar

graph and list shutter speeds from 1 through 2000, If

there is no display and no battery check in the previous
step, there is a power circuit problem. Test power
consumption,

4. Watch the viewfinder LCD as you change aperture,

ASA, and scan different subject brightnesses. The bar
graph should change one Ev for each Ev change you
make with the controls. If changes are erratic, wipers are
dirty or making poor contact. If there is no change with
brightness, look for the word "Memo" in the LCD. If it is

flashing, memory has been set Move the control switch
to "Clear" to reset the system. Still no change in the bar
graph with light suggests a flex or IC problem,

5. If LCD response was normal in step 4, press the

"Spot" button while the circuits are on. The word "Spot"
should appear and the bar graph should remain
unchanged with light. Try several more tests for spot

metering on different subject brightnesses. The bar graph

should adjust to an average of the settings. Also

test

"Highlight" and "Shadow" buttons. Finally, move the
control switch to "Clear." The "Auto" mode with bar
graph should reappear If any functions fail, the most
likely cause is poor switch contact or a broken connection
to the top cover.

6. See if "Auto" exposure (without "Spot") delivers

speeds near to bar graph indications, (Be sure to use film
or similar material in front of pressure plate.) If the
speeds sound fast, check the aperture. If speeds do not
match LCD indications, there is an off-the-film circuit

problem.

7. See if "Spot" mode speeds correspond to the bar

graph. If not but the "Auto" speeds do, there is a possible
problem with IC-102 or the variable resistors. If speeds in

steps 6 and 7 are both wrong, there is a problem with

MG-2's circuit or the timing switch.

8. Test several shutter speeds in "Manual" mode. If the

speeds are incorrect, but "Spot" speeds are normal,
suspect the TV-VR under the shutter board. If manual
speeds are normal but "Spot" are not, there is a logic
problem between IC-101 and IC-102 — probably an open
connection.

9. Apply 2 volts (—) to the wind-side flash dedication
contact with the mode set to "Auto" and circuits on. The
"Flash" LED should appear in the viewfinder and the
shutter speed should be near 1/60.

10. Try the auxiliary functions such as self-timer and

LCD lamp switch.

Finally, always keep these important facts in mind:

A. "Auto-Average" exposure is controlled by IC-103 at

the time, of exposure and may not be what the LCD
indicates in advance.

B. "Spot" and "Manual" exposures are calculated in

advance by the CPU and are indicated by the LCD,

Those exposures should always equal the indication.

OLYMPUS OM-4, PAGE 4