Mother Unit; Sub-Power Switching; Sub-Power Control; Secondary Side Voltage Detector - Kenwood pds20-18 Service Manual

MOTHER UNIT (X67-1420)
+15 V Rectifier and Smoother
A m o n g e l e c t r i c p o w e r t r a n s m i t t e d f r o m t h e
pri ma ry si de t hro ug h th e m ai n tra ns fo rme r (T 1) ,
this circuit produces rectified and smoothed +15 V to
be supplied to IC1 in the AC unit.
Main Power Primary Side Rectifier
and Smoother
Diode D1 rectifies AC power and capacitor C4
smoothes it.
Capacitor C4 stores voltage about
high as the AC voltage.

Sub-Power Switching

Electric power having passed through diode D1 and
sto red in ca pac it or C4 pas ses t hro ugh th e s ub -
transformer (T1) and is switched by Q 1 by mean s
of ringing choke conversion (RCC). The oscillation
frequency is about 60 kHz when the input AC
voltage is 100 V or about 120 kHz when the input
AC voltage is 200 V. Q1 is controlled by signals
from the sub- power control (D).

Sub-Power Control

PH1 and IC2 o utput signal s from the ci rcuit (J) fo r
det ect in g t he vo lta ge of th e int er nal +5 V po we r
(CPU unit). This sub-power control circuit controls
switching of Q1 based on such signals.
Internal -3.5 V Rectifier and Smoother
This circuit produces rectified and smoothed internal
v ol ta ge of 3 .5 V at p ins 1 5 a nd 1 6 o f the s ub -
Tra ns fo rm er (T 1) , wh ic h s up pl ie d to th e po we r
Unit (X68-1970-0x) and control unit (X77-2120-0x).
Internal 15 V Rectifier and Smoother
Th i s c ir c u i t p r o d u ce s r e ct i f i e d a n d sm o o t h e d
Inte rnal v ol tage of 15 V at pin s 10 to 12 o f th e
sub-transformer (T1), which is supplied to the
power
unit (X68-1970-0x) and control unit (X77-2120-0x).
PDS20-18/PDS36-10/PDS60-6
CIRCUIT DESCRIPTION
Internal
Th i s c ir c u i t p r o d u ce s r e ct i f i e d a n d sm o o t h e d
In te rn al v ol ta ge o f
sub -T ra ns fo rm er (T 1) , wh ic h is su pp li ed t o th e
AC unit (X68-1980-0x).
Internal +5 V Rectifier and Smoother
Th i s c ir c u i t p r o d u ce s r e ct i f i e d a n d sm o o t h e d
Internal voltage of +5 V at pins 13 and 14 of the sub-
Transformer (T1), which is supplied to the CPU unit
(X77-2110-00).
2 times as

Secondary Side Voltage Detector

This circuit detects voltage using R22 and R23 and
outputs control signals to the sub-power control (D)
throu gh PH 1 and IC2 in o rder to ma ke th e int erna l
+5 V constant.
Main Switch Control
Thi s c ir cui t shu ts do wn th e m ai n s wi tch t hro ug h
PH2 using the Trip+ signal from the control unit.
15 V Rectifier and Smoother
1 5 V a t pi ns 7 t o 9 of t h e
9