Bulletin Hk2002-04 - Harman Kardon AVR8000 Service Manual

AVR8000
harman/kardon
Service bulletin # H/K2002-04 April 2002
To: All harman/kardon Service Centers
Model: AVR8000
Subject: Idle Current Adjustment Procedure
In the event you receive an AVR8000 with the complaint "The receiver is overheating, or the protection
circuit is engaging, or intermittently shutting down after the unit warms up" the DC idle current should
be checked and adjusted as described below. Top cover may feel abnormally hot to the touch.
Synopsis: Set DC idle current of output devices by adjusting five potentiometers
Specialized equipment/parts needed:
Variable AC transformer ("Variac" type) to adjust and monitor AC line voltage.
Two pin harness plug to connect DMM to idle current test points. Order hk part# 55212910NR.
Note: Unit that no longer functions when cool may have damaged components: output transistors, resistors,
diodes, etc, in the output stage which must be replaced before performing adjustment so protection circuit is
not activated.
1) Unplug any external connected cables to the AVR8000.
2) Remove the top cover, (18) black Phillips screws.
3) Locate the five idle current-current adjustment potentiometers (see illustration page 2). Facing the front of
the AVR8000, they are located on the left and right sides of the unit along the top of the vertical PCB's.
They are also marked on the PCB's "Idle-Adj."
4) The white 2 pin Connectors (test points) and their related adjustment pots are referenced below. First,
with the unit turned OFF, adjust with a small screwdriver so that all idle current pots are "centered".
Test Point (Check with DMM)
CP903
CP904
CP922
CP923
CP924
Do not confuse the idle current adjustments with the DC offset adjustment pots which are located
directly adjacent to them !
5) Replace the top cover (no screws); turn unit ON. Unit should be connected to a "Variac" type (variable
transformer) adjusted to 120VAC. Let receiver idle with no load, no signal input, and volume control at
minimum (full CCW), for five minutes to stabilize the amplifiers.
6) Remove cover again. Plug in the two pin harness plug at first test point and connect to DMM set on the
mV scale. Check and adjust AC line voltage to 120 volts again if necessary. Using a non-metallic
screwdriver, adjust each of the idle current pots, one at a time, in the following manner: The final desired
voltage at each test point is 10.5 mV, but you should arrive at this voltage by reducing a higher amount in
25% increments with each adjustment, with the final adjustment set at 10.5 mV. This adjustment should
be made gradually in steps, so the amplifiers will have time to stabilize. Repeat this procedure at least
three additional times, each time replacing the top cover (no screws necessary), and letting unit idle
turned ON for at least five minutes between each adjustment. Monitor the AC line voltage and adjust to
120 volts when necessary.
7) If a wattmeter is available, total wattage drawn from line should be 165 to 170 watts at idle.
8) Replace the top cover and screws after the final adjustment.
Service Bulletin
Warranty labor rate: MINOR repair
Adjust Idle current Pot
Affected by
Affected by
Affected by
Affected by
Affected by
15
harman/kardon
VR902
VSR902
VC902
VL902
VSL902