Harman kardon hk 300 xm service manual

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PRECAUTIONS

1.

Always disconnect the chassis from power line when soldering. Turning the power switch OFF is not enough. Power line
leakage passing through the heating element may destroy the transistors.

Never attempt to do any work on the transistor amplifiers without first disconnecting the AC line cord and waiting until
the power supply filter capacitors have discharged.

Replacement for output and driver transistors, if necessary, must be made from the same beta group as the original type.

If one output transistor burns out (open or short) always remove all the output transistors in that channel and check the bias
adjustment, the control and other parts in the network with an ohmmeter before inserting a new transistor. All transistors
in one channel will be destroyed if the base biasing circuit is open on the emitter end.

When mounting a replacement power transistor, be sure that the bottom of the flange, the mica insulators and the surface of
the heat sink are free of foreign matter, for they may cause transistor failure.

Silicon grease must be applied between the transistor and the mica insulator, and between the mica insulator and the heat
sink for better heat conduction.

Fuses must be replaced with size and type indicated. Use of other types can expose components to destructive current levels.

ALIGNMENT PROCEDURES

General Conditions (unless otherwise noted)

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Tape Select Switch is LN position.

Dolby NR Switch is OFF position.

Dolby HX Switch is OFF position.

MPX Filter Switch is OFF position.

Line Level Controls at maximum.

Output Level Control at maximum.

Bias Fine Trim Control at center.

Microphone Level Controls at minimum.

Connect 10 k9. (1/4 W) carbon resistors across both left and right line output jacks.

vrvm oscmoscope
TAPE OUTPUT -.__ _
R
u 0
Q 0
n
Fneouencv
I] L Cl El :xé/é/E' =' a ll COUNTER

DEUCE
ooO o©©' g

VARIABLE RESISTOR

M01
DC MOTOR

9___-

REC/PLAY
HEAD

HEAD AZIMUTH

ADJUSYMENT scnew Fig. 1

Noise Reduction System and Headroom Extension System manufactured under license from Dolby Laboratories Licensing Corporation.
Dolby and the double-D symbol are trademarks of Dolby Laboratories Licensing Corporations

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