Kenwood KRC-646D Service Manual page 8

Component
CIRCUIT DESCRIPTION
Use/Function
Operation/Condition/Compatibility
Q27
LW PLL LPF inhibition switch
Q28
FM/MW PLL LPF gain select
Q29,Q31
FM/MW PLL LPF
Functions only when FM or MW is selected. Supplies Vt.
Q30,032
|
LW PLL LPF
Functions only when LW is selected. Supplies Vt.
Q33
METAL SW
Turns OFF when METAL is selected.
Q34,035
4
MONO/STEREO switch
L only : Turns OFF when MONO is selected and turns ON when STEREO
is selected to control the STEREO circuit of MPX.
Q36,0Q37
SK key input contro!
Donly : When SDK mode is selected and SK is present, Q36 is OFF and Q37 is
ON. This turns 1C4(1/4) output to 'L"' so that the data "SK input is
present'' is transmitted to the SK input of 1C1. When SK is not present,
it executes the operation in reverse way as above. When SK signal is not
present for more than 5 seconds, starts SK Seek operation.
Q38
SD Key input control
When ANT input level is more than Seek stop level, Q38 is turned ON. This turns
the 1C4(4/4) output to "L'' so that the data "SD input is present" is transmitted
to the SD input of 1C1, When ANT input level is lower than the Seek stop level,
it executes the operation in reverse way as above.
Q39 ,Q40
—+
ST key input control
——-
When ST is present, O39 is turned OFF and Q40 is turned ON, and it turns IC4
(3/4) output to ''L" so that the data ''ST input is present" is transmitted to ST
input of 1C1. When ST signal is not present, it excutes the operation in reverse
way as above.
Q41
TAPE/RADIO select control
Donly : !n SDK mode during TAPE operation, it is turned ON when interrupt-
ed by DK, and outputs "L"' signal then turns !C4(1/4) output to "L"
and transmits the RADIO select data to change to the RADIO mode.
Also, it turns the !C3(2/4) output to ""L"' and Q18, Q17 to OFF and
releases the head. At this time, the output of 1C5(2/4) is turned to 'L"
and makes the SK ON/OFF circuit ON status to inhibits the SK OFF
operation by fluctuation of electric field.
042
SK ON/OFF control
043,044
MW/LW select
When MW is selected, the output of 1C2(6/6) goes ''H" and 043 and O44 are
turned ON, then + 9V signal is applied to the BS pin of AM tuner so that the
AM tuner is set to the MW mode.
Q45 ,046
DK interrupt switch
Q47 048
LOUDNESS switch
Q49 ,Q50
Audio mute