background image

3. Automatic by Memory

Closing the "Memory" switch in either automatic

mode instructs the CPU to store the brightness reading

used in the last exposure. That is, after the shutter has

run, the same speed will be used for all subsequent
exposures regardless of light conditions. Changes in
aperture and ASA will cause comparable changes in
shutter speed. The condition will remain for about one

hour or until the "Clear" switch is closed,

The first Auto-by-Average exposure in Memory mode

will be off-the-film using IC-103's integrator All other
exposures will be controlled by IC-102 in the same

manner as for Auto by Spot.

4. Manual by Average

Manual speeds are selected by turning the speed

selector ring behind the lens. A variable resistor
(TV-VR) under the Shutter Board is turned by a gear
coupled to the speed selector ring. In manual mode the

CPU instructs IC-102 to convert voltage changes from

the TV-VR to binary code along with voltage changes
from brightness, aperture, and ASA.

The CPU calculates proper exposure based upon ASA

and light. The difference between the correct exposure
and that resulting from aperture and speed settings is
indicated by the bar graph in the viewfinder display.

When the two are equal, the end of the bar graph is at the
index mark in the center.

Shutter speed is controlled by IC-102 in the same

manner as Auto by Spot. The current to charge C-104 is

proportional to the manual speed selected.

5. Manual by Spot

Exposure calculations by the CPU are based upon an

average of up to eight spot light readings. The bar graph

indicates the result of this average, Shutter speed control
is the same in all manual modes, since the speed selected
will be used regardless of exposure error.

6. Highlight and Shadow

In any "Spot" mode of operation, pressing the "Hi,

Light" or "Shadow" switches will change the indicated
exposure. "Shadow" shortens exposure time by about 2 1/2
Ev, while "Hi. Light" extends exposure time by 2 Ev. In
auto modes, the actual shutter speed is changed
accordingly,

7- Off-The-Film Flash Exposure Control

When a suitable flash, such as the T-32, is installed on

the camera, operation changes to Off-The-Film Flash

mode. All other modes are cleared by the flash operation.

The CPU gathers light, ASA, and aperture conditions,
then calculates an exposure. If shutter speed is less than

1/60, the flash will be triggered during exposure. Light

from the flash is integrated by IC-I03, the same as Auto

by Average mode. When a proper exposure has been
made, pin 48, IC-102 goes high signaling the flash

through its dedication contact. The flash quenches, the
shutter times out at 1 /60 second, and the system resets for
the next exposure.

After a flash exposure, the strobe LED (viewfinder)

will flicker if exposure was correct. For insufficient light,
the "Under" LCD will flicker and the "Over" LCD flickers
to indicate too much light.

The Sync Switch does not connect directly to the hot

shoe contact. When the opening curtain runs to close the
Sync Switch (X-Contact), pin 59, IC-102 is connected to
the chassis or B+, Pin 50, IC-102, then goes low to turn on
transistor Q-101. Q-101 switches B+ to the gate of an
SCR which turns on to connect the hot shoe contact to
the body. If the auto speed will be faster than 1/60, the
SCR is not switched on and the flash does not fire.

Connecting the positive side of a 2v power source to the

shoe and the negative side to the right-side dedication
contact should set flash mode operation. The red LED
indicating the flash symbol will light in the viewfinder
and shutter speed will be 1/60.

Readout

The LCD viewfinder indication is driven by IC-104

situated under the flex circuit between the prism and

rewind shaft. Capacitor C-302 between pins 3 and 4,

IC-104, acts as a voltage booster (+/- 3v to Vcc) to

provide the necessary 6 volts to operate the LCD, Power
(Vcc) is supplied through transistor Q-301 (PNP) which
is controlled by pin 54, IC-102.

As the CPU determines exposure and mode, that

information is transmitted to IC-104 for decoding and
display, Data transmission takes place about once every

100ms through a series line,

1. Data Sync signal is sent from pin 12, IC-101 to

pin  l l

s

 IC-104.

2. Timing clock signal is sent from pin 10, IC-101 to

pin 13, IC-104.

3. Series data is sent from pin 11, IC-104 to pin 12,
IC-104.

The display is made up of 41 horizontal rows and back

plates in three vertical rows. Voltage differences of 4.0v

between any horizontal and vertical will result in that

segment being darkened. There is a RAM included inside

IC-104,

There is a backlight lamp for viewing the display in

dark conditions. Pressing the "Lamp" switch sets the
light on for about 8 seconds.

OLYMPUS OM-4, PAGE 3

Содержание OM-4

Страница 1: ...going to the viewfinder to the photodiodes on IC 103 A BV voltage changing 18mv Ev with light is output from pin 16 IC 103 to pin 7 IC 102 At the same time IC 102 watches aperture setting AV VR at pi...

Страница 2: ...e the equivalent ofexposure with a signal from pin 80 to pin 14 IC 103 Voltage on the integrator s output begins to increase at a rate proportional to light intensity at the film plane The same voltag...

Страница 3: ...ight ASA and aperture conditions then calculates an exposure If shutter speed is less than 1 60 the flash will be triggered during exposure Light from the flash is integrated by IC I03 the same as Aut...

Страница 4: ...ry 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...

Страница 5: ...Pins 16 and 17 Memory Yellow to Brown or Pins 18 and 14 Clear Yellow to Red or Pins 16 and 18 8 The circuit may be cleared by moving the Mode Switch to the battery check position 9 Take care to avoid...

Страница 6: ...o metering mode You can drive the circuit bonkers with random highs to pin 30 Pin 31 is output to Memory LED on Spot button Pin 32 is output to Q 105 to operate LCD backlight lamp Pin 33 is output to...

Страница 7: ...CPU Pins 21 and 22 are mode control from CPU Pins 56 55 IC 101 Pin 23 is signal from CPU to power LCD Pin 24 is power on signal from IC 101 Should go high when release is pressed one half stroke Pin 2...

Страница 8: ...Pin 60 is charge signal to C 201 for MG 1 Voltage will pulse high at release then fall to near zero to recharge C 201 Pin 61 is release signal to Q 201 for MG 1 Pulses low for release Pin 62 is B in...

Страница 9: ...ives under a circuit board between the prism and ASA resistor It is not easy to reach for tests but important inputs can be checked at ICs 101 and 102 Its output of course is the LCD Pin 1 is CLK inpu...

Страница 10: ...de Manual and Spot Auto speeds are normal LCD normal 1 A 1 B 2 A 2 B 2 C 3 A 3 B 4 A 4 B Shutter slow or open in Manual and Spot Average Auto Average speeds normal LCD normal Shutter fast or running t...

Страница 11: ...1 Power Circuit Malfunctions A External Observations No LCD No battery check No shutter operation except mechanical OLYMPUS OM 4 PAGE 11...

Страница 12: ...B External Observations Batteries run down quickly Shutter functions may or may not be normal LCD may or may not function OLYMPUS OM 4 PAGE 12...

Страница 13: ...or under Spot Auto speeds slow Auto speeds slow or normal Manual speeds normal First check bar graph response to light ASA and AV changes to isolate problem Follow the same pro cedure as 2 A but look...

Страница 14: ...onnects across pins 7 and 8 IC 102 Value is 0 015 MF 2 Check if bar graph is stable in BC mode If so check R 130 near IC 101 3 Check for dirty wipers on AV VR and SV VR 3 Release Malfunctions A Extern...

Страница 15: ...Shutter releases once then will not release again until circuit is reset LCD normal 4 Shutter Malfunctions A External Observations Shutter stays open in Auto and Manual Mechanical speeds OK LCD norma...

Страница 16: ...ual speeds normal Spot Auto speeds normal LCD normal C External Observations Shutter slow or open in Manual Shutter slow or open in Spot Auto Auto speeds normal LCD normal Note Be sure LCD indicates c...

Страница 17: ...D External Observations Shutter fast or runs through Auto and Manual LCD is normal Mechanical operation is normal OLYMPUS OM 4 PAGE 17...

Страница 18: ...mal LCD is normal G External Observations Manual speeds not correct or won t respond to adjustment Auto mode speeds OKt 1 Check each Manual speed with LCD If LCD does not correspond to speed dial TV V...

Страница 19: ...5 Display Malfunctions A External Observations No LCD or weak or erratic Shutter functions normal Exposure is normal OLYMPUS OM 4 PAGE 19...

Страница 20: ...isplays wrong characters for mode Shutter function appears to be normal Look for poor solder connections at wires to Display Board 6 Flash Malfunctions A External Observations Flash will not fire Flas...

Страница 21: ...r not working Self timer function is normal 1 For LED apply B to pin 41 IC ID2 through 1000 ohm probe If LED flashes IC 102 may be defective If no LED check B to LED Black wire from TP 1 Also Q 401 an...

Страница 22: ...OLYMPUS OM 4 PAGE 22...

Страница 23: ...OLYMPUS OM 4 OLYMPUS OM 4 PAGE 23...

Страница 24: ...s a violation of the law Willful violations of the been taken in the preparation of this manual the publisher Copyright Law of the United States can result in civil assumes no responsibility for any e...

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