Harman kardon hk 450

Page 2

PRECAUTIONS

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.

NOTE TO WARRANTY STATIONS: Printed circuit board assembly numbers are
shown for reference only. Harman/Kardon does not normally supply assembled
printed circuit boards.

NOTE: To speed handling of your order be sure to include both the model and
serial numbers, in addition to the quantity, part number and part description of
the items ordered. Orders from independent dealers, independent servicemen, and
retail customers will be shipped on a cash in advance basis. Harman/Kardon
reserves the right to substitute equivalent parts for those originally installed in
this chassis. All parts should be ordered from Harman/Kardon, 55 Ames Court,
Plainview, L.l., N.Y. 11803, Att: Parts Department.