First Mixer - Kenwood TS-590SG Service Manual

TS-590SG
Ext. Speaker (second priority)

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 JFET (Q263 to Q266), and mixes with LO1 (12.495
to 32.195MHz) which is approximately +18dBm, and con-
verts 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 JFET (Q321 to Q324), and mixes with LO1 (73.120
12
CIRCUIT DESCRIPTION
IF input
(10.695M/11.374M)
D526
Switching
SSB, CW, AM
XC1-024 (A/2)
IC631
Multiplexer
FM
(AF)
SSB, CW, AM
(24kHz)
Headphone (first priority)
(XC1-022 F/6)
(XC1-024 A/2)
Int. Speaker (third priority)
(X45-398 A/2)
Fig. 5 From second IF to AF output
Q263
L261 VR261
RF
Q264
L262
LO
12.495~32.195MHz
Fig. 6 First mixer circuit of the RX-1 path
FM
IC591
FM IC
IC592
CF591
FM AF Amp
455kHz BPF
BW: 12kHz
Option Filter
BW: 9kHz
D551,D552
Q551
RX 3rd Mixer
IF Amp
XC1-021 (A/3)
IC64(A/2)
Buffer
RIF
IC64(B/2)
Active LPF
Q62 IC69
IC67 AF Mute (A/2)
AF
AF Power
Amp
AMU
to 133.095MHz) which is approximately +18dBm, and con-
verts into the fi rst IF (73.095MHz). No bias is added to this
LO1.
The volume resistance (VR261, VR321) within the first
mixer circuit is used to adjust mixer balance. After replac-
ing the JFET (Q263~Q266, Q321~Q324), transformer (L261,
L262, L264, L323, L324, L326), volume resistance (VR261,
VR321), or TX-RX unit (XC1-024 A/2), adjust the mixer bal-
ance in the adjustment mode.
+14V
Q265
Q266
+2.6V
FM
(AF)
SSB, CW,AM
(24kHz)
IC65(A/2)
Active LPF
IC66
A/D
Conv.
IC65(B/2)
Active LPF
IC301
DSP
IC69 IC71
(B/2) (B/2)
IC72
D/A
Conv.
Active LPF
L264
1st IF
11.374MHz