Kenwood TS-590S, Service Manual

Page: 12 / 162

TS-590S
12
First Mixer
There are 2 types of first mixers: for IF frequency
11.374MHz RX-1 path, and for IF frequency 73.095MHz
RX-2 path.
The fi rst mixer for the RX-1 path is a quad-balance type
mixer by MOS FET (Q263 to Q266), and mixes with LO1
(12.495 to 32.195MHz) which is approxi18dBm,
and converts into the fi rst IF (11.374MHz). Approximately
2.6V bias is added to LO1 in order to suppress distortion.
The fi rst mixer for the RX-2 path is a quad-balance type
mixer by MOS FET (Q321 to Q324), and mixes with LO1
Fig. 5 From second IF to AF output
CF591
455kHz BPF
BW: 12kHz
IC592
FM AF Amp
FM
(AF)
Option Filter
BW: 9kHz
SSB, CW, AM
D551,D552
RX 3rd Mixer
FM
IC591
FM IC
D526
Switching
IF input
(10.695M/11.374M)
Q551
IF Amp
SSB, CW,AM
(24kHz)
FM
(AM)
RIF
AF
Active LPF
AMU
SSB, CW, AM
(24kHz)
Headphone (first priority)
(X54-370 F/6)
Ext. Speaker (second priority)
(X57-785 A/2)
Int. Speaker (third priority)
(X45-391 A/2)
IC631
Multiplexer
IC64(B/2)
Active LPF
IC64(A/2)
Buffer
IC65(A/2)
Active LPF
IC65(B/2)
Active LPF
IC71
(B/2)
IC69
(B/2)
IC69
(A/2)
AF Power
Amp
IC67
Q62
AF Mute
X57-785 (A/2) X53-446 (A/3)
IC66
A/D
Conv.
IC72
D/A
Conv.
IC301
DSP
(73.120 to 133.095MHz) which is approxi18dBm,
and converts into the fi rst IF (73.095MHz). No bias is added
to this LO1.
The volume resistance (VR261, VR321) within the fi rst
mixer circuit is used to adjust mixer balance. After replac-
ing the MOS FET (Q263~Q266, Q321~Q324), transformer
(L261, L262, L264, L323, L324, L326), volume resistance
(VR261, VR321), or TX-RX unit (X57-785 A/2), adjust the
mixer balance in the adjustment mode.
Fig. 6 First mixer circuit of the RX-1 path
LO
12.495~32.195MHz
+14V
+2.6V
Q263 Q265
Q264 Q266
VR261
L264
1st IF
11.374MHz
RF
L261
L262
CIRCUIT DESCRIPTION