Sansui AU 217 Service Manual

Page 3

217

2. OPERATION OF DRIVER SECTION

fig. 2-1 Driver Section

+35V

§
7" :
BIASVR i. K TRII

>

KTRos -
B

-35V

3. ADJUSTMENT

oThe first stage on driver section employs a differential

amplifier circuit, therefore one of two output signals from
ICOI on the driver section is supplied to base of TROS and
the other is added to base of TRO9.

The input phase of the current mirror circuit including
TROS and D01 is inverted by TROS and its inverted signal is
added to base of TR07. Since the input signals] A 8r B, as
Fig. 2-1, of TRO7 and TR09 are in same level and inphase,
the function of this section is complete push-pull operation
by which even harmonic distortion is extremely decreased.

1) Bias Current Adjustment (See the Picture of Top View on page 7)

(Measure output on both channel)

TRI7.18
Note: 1. Confirm the AC Power Supply voltage,
2. Master Volume ....Minimum VOHmEIEIQ
3. Room Temperature .18 C~28° C mV
(65° F~83° F) _- Ii : m
4. For this adjustment, run the unit for more than 3 l, V ® = 7
minutes after power is switched ON. 6 D33
5. Before this adjustment, turn VRO1 and VROZ fully R4950 : 21 2 mA
counterclockwise. I
TFHQ'ZO Volt metere
(L-CH. . . .R49 and R-CH. . . .RSO)
(l-CH. , . .TRI7, TRI9 and RCH.. . rTR18, TR 20) ' I
STEP SUBIECT EQUIPMENT MEASURE OUTPUT ADIUST ADJUST FOR
1 Bias Current DC Volt Meter TP Termina|(+)(-) F-2760 DC 7mV i0.5mV
L-CH of F-2760 VROl
2 Bias Current DC Volt Meter TP Termina|(-i-)(~)
R-CH of F-2760 VROZ

i
l
F-2760 DC 7mV :tO.5mV
2