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The Harman Kardon
Model HD755 silver
COMPACT DISC PLAYER
Technical Manual
HD755
Standby
CONTENTS
1. LASER BEAM SAFETY PRECAUTIONS ............. 2 9. BLOCK DIAGRAM ............................................. 54
2. CONTROL AND FUNCTIONS ............................. 4 10. SCHEMATIC DIAGRAMS .................................. 55
3. SPECIFICATIONS AND FEATURES ..................... 7 11. PCB LAYOUT ..................................................... 59
4. AUDIO CHARACTERISTICS TEST PROCEDURE 12. EXPLODED VIEW .............................................. 62
.............................................................................. 9 13. PACKING DRAWING ......................................... 63
5. CIRCUIT DESCRIPTION ....................................11
6. CRITICAL I.C. SPECIFICATION ........................ 15
7. PART LIST ......................................................... 41
8. TROUBLE SHOOTING GUIDE .......................... 48
* Harman/ kardon continually strives to improve its products. The HD750 Compact Disc Player design and
specifications are subject to change and may differ from the published specifications and descriptions, but will
always equal or exceed the original specifications unless otherwise stated.
DANGER: Invisible laser radiation when open and interlock failed or defeated.
AVOID DIRECT EXPOSURE TO BEAM.
Parts and Service Office
250 Crossways Park Dr., Woodbury, N.Y. 11797
1112-FL8350 P9603 1200 Printed in Hong Kong
HD755
LASER BEAM SAFETY PRECAUTIONS
CLASS 1 LASER PRODUCT
CAUTION
Invisible laser radiation when the unit is open.
Do not stare into beam.
CAUTION: USE OF ANY CONTROLS, ADJUSTMENT, OR
PROCEDURES OTHER THAN THOSE SPECIFIED HEREIN
MAY RESULT IN HAZARDOUS RADIATION EXPOSURE.
Do not look directly at the laser beam
coming from the pickup or allow it to
strike against your skin.
This compact disc player uses a pickup that emits a laser beam. The laser beam is emitted from the
location shown in the figure. When checking the laser diode, be sure to keep your eyes at least 1 foot away
from the pickup lens when the diode is turned on. Do not look directly at the laser beam.
CAUTION:
Using controls and adjustment, or doing procedures other than those specified herein, may result in
hazardous radiation exposure.
2
HD755
SAFETY PRECAUTIONS
This symbol is intended to alert the user to
the presence of uninsulated "dangerous
voltage" within the product's enclosure that
may be of sufficient magnitude to consti-
tute a risk of electric shock to persons.
This symbol is intended to alert the user to
the presence of important operating and
maintenance (servicing) instructions in the
literature accompanying the appliance.
Caution: To prevent electric shock do not use this
(polarized) plug with an extension cord, recep-
tacle or other outlet unless the blades can be
fully inserted to prevent blade exposure.
Attention: Pour prevenir les chocs electriques ne pas
utiliser cetre fiche polarisee avec un
prolongateur, une prise de courant ou une au-
tre sortie de courant, sauf si les lames prevent
etre inserees a fond-sans en laisser aucune
WARNING partie a decouvert.
To prevent fire or shock hazard, do not
expose the unit to rain or moisture.
HANDLING LASER PICKUP
The laser diode in the optical system of this player can be damaged by electrostatic discharge from
your clothes or your body. Proper electrostatic grounding for service personal is required during servicing.
BEFORE REPAIRING THE COMPACT DISC PLAYER
Preparation
Human Body Grounding:
Many of the components used in this compact disc player, including the laser pickup, are sensitive to
electrostatic discharge. Service personal should be grounded with an electrostatic armband (1 Mohm).
Caution:
Static charge on clothing does not escape through a body grounding wrist band.
Be careful not to contact the pickup or electrical components with your clothing.
Workbench and Tool Grounding:
A properly-grounded electroconductive plate (1Mohm) or metal sheet should be fitted to the workbench
surface. Tools and instruments (such as soldering irons and scopes) should be grounded to prevent AC
leakage.
Note: Laser diodes are so susceptible to damage from static electricity that, even if a static discharge does
not ruin a diode, it can shorten its life or cause it to work improperly.
3
HD755
Front Panel Controls
1 1
2 4 13 11 17 16 15 10 9
Standby
1 2 3 4 5 6 7 8
0 Power Switch 5 Open/Close Button A Repeat Button 16 Random Button
1 Status Mode Indicator 6 Search Button B HDCD Indicator 17 Repeat Button
2 Headphones Jack 7 Skip Button C Information Display
3 Headphones Level Control 8 Stop Button D Remote Sensor
4 CD Drawer 9 Play/Pause Button 15 Program Button
0 Power: Press this switch to apply power to 3 Headphones Level Control: Turn this knob 9 Play/Pause Button: Press this button to
the HD750. Then the Status-Mode Indicator to increase or decrease the volume level for start the playback of a CD. If the CD drawer is
1 will turn green, the Information Display headphones connected to the HD750's open, pressing this button will automatically
C will illuminate and all trays will be checked Headphones Jack 2. Note that changing this close the drawer. When a disc is playing press
automatically for discs. Press the switch again to level will not change the sound level for the this button once to momentarily stop a disc.
turn the unit off; the Status-Mode Indicator unit's main output, as that remains constant. When the button is pressed again, the disc will
1 will turn amber, indicating that the unit is in resume play at the point it was stopped.
4 CD Drawer: This drawer holds the discs
Standby. When the HD750 is connected to a
that will be played. Press the Open/Close but- A Intro Button: Press this button to put the HD750
switched AC outlet, such as those found on the
ton 5 to open the drawer so that discs may be in teh Intro Scan mode. When you press the button, the
back of many audio products, and the AC outlet
inserted. unit will play the first 10 sec of each track on the disc, and
will be turned on, the unit will turn to Standby
then move to the next track. Press the button again to
mode only. 5 Open/Close: Press this button to open or
defeat the function and continue full play of the current track
close the disc drawer. DO NOT push the drawer
1 Status-Mode Indicator: When the
to close it or damage to the transport mecha- B HDCD Indictaor: The LED will light automatically
HD750 is in the On mode, this indicator will
nism may result. when a CD with HDCD encoding is playing. No
glow green. When the unit is off, the indicator
further action is needed to enjoy the benefits of HDCD.
will glow amber, indicating that the unit is still 6 Search: Press one side of this button to
connected to AC power. search forward -- or the other side of the C Information Display: This display
button to search backwards , through a provides details about the operation of the
2 Headphones Jack: Connect a set of stan-
disc to locate a particular portion of the disc HD750.
dard headphones to this jack for private listening.
being played.
D Remote Sensor: The sensor behind this
1 Program Button: This button is used to
5
7 Skip: Press the right side of this button to window receives commands from the remote
program the playback of a disc in a particular
move to the next track fl