JVC RX-D201, Training Book

Page: 62 / 105

•With Q1101/1102 disconnected, the DCDC CONVERTER CONTROL
SECTION can function normally; and it is safe to check the circuit.
•The DC level at pin 3 of IC112 controls the pulse width of the clock at pin1
and it farther controls the DC level of the ‘AMP +/- B’.
•The DC level at pin3 of IC112 is effected by ‘Vout_DET’, ‘VCHANGE_1,
VCHANGE_/2, and ‘FEEDBACK’.
•Until the AMP_+/-B voltages are stabilized, Q1772 and Q1773 are active.
After the mentioned voltages are stabilized, the two transistors turn off. If
the PWM too wide at IC113 pin11, it will be turned on Q1173 and shuts off
the AMP_ +/-B.
•Connect the ‘Vout_DET’ (CN152 pin 4) to ground (or to +12v) through 1K
Ohm resistor. This makes PWM duty cycle change at CN152 pin 11.
Otherwise this board is defective.
•CN152 has 12 pins on models RX-D401/402/702; the 12th pin is for SSS
(Smart Surround Setup) function ON/OFF.
•The purpose to add 47k Ohm resistor is eliminate the noise at the
‘AMP_ +/-B’ when power switch ON/OFF, this noise may cause Q1101 and
Q1102 to become damaged.
•To prevent noise when power is switched ON, do not touch the signal path
that connect to the Gate of the MOSFETs until the power becomes stable.