Advertisement
• The AMP + B voltages vary from about +25v to +42v; depending on the power output of 7
channels at final stage before speaker terminal (The voltages are higher in models
RX-D401/402/702)
• When the audio output level (the analog negative feedback [A NFB] that comes from the
audio final output) is increasing, the DC level at the cathode of diodes D211-D311...
(7 diodes) is increased proportionally.
• This increased DC voltage via buffer Q1501 turns on Q541 first (0.7v), and will turn on
both Q541 and Q542 if the DC level rises higher (2.57v). Then the low state will input to
pins 66 and 90 of IC501 (OUT_LEVEL 1 and OUT_LEVEL 2). This causes IC501 to output
a low state on pins 62 and 65 (V CHANGE_1 and V CHANGE_2) to DCDC CONVERTOR
CONTROL board.
• These low state inputs (through CN151 pin 7 & 8) switch off Q1151, Q1152, and it effects
the DC level at pin 1 of IC111 (error amp). Finally, it changes the PWM pulse's duty cycle
duration at IC112 pin 1, thus rises the AMP + B voltage to around + 35v ( VCHANG_1
active only) or + 42v (both VCHANGE_ 1 and _2 are active).
• The 'FEEDBACK' from 'AMP+B' goes into ERROR AMP IC111 pin 3 through CN151 pin 2,
it is for stabilizing the 'AMP+B' regulation.
CPU IC501
PIN 62
PIN 7
CN151
H
L
L
PIN 65
PIN 8
AMP +/- B
H
25V
H
35V
L
42V
POWER SUPPLY 3/5
Hide quick links:
Advertisement
