Kenwood TS-990S Service Manual

TS-990S
19
CIRCUIT DESCRIPTION
Table 12 BPF range
Band Filter range
135kHz 30~522kHz
BC 522kHz~1.705MHz
1.8MHz 1.705~2.5MHz
3.5MHz 2.5~4.1MHz
5MHz 4.1~6.9MHz
7MHz 6.9~7.5MHz
10MHz
7.5~10.5MHz
10.5~13.9MHz
14MHz 13.9~14.5MHz
18MHz
14.5~21.5MHz
21MHz
28MHz 21.5~30.0MHz
50MHz (TX) 49.0~54.0MHz
50MHz (RX) 30.0~60.0MHz
4-2. From the Sub Preamplifi er (Q219) to the 2nd IF
Frequency (10.695MHz/11.374MHz)
The signal from the sub preamplifi er (Q219) to the 2nd
IF amplifi er (Q481) is separated into two paths, SRX-1 and
SRX-2, depending on the frequency band (Refer to Table
13.). The SRX-1 path is selected if the “L” signal is input to
Q958, and the SRX-2 path is selected if the “H” signal is in-
put.
The signal on the SRX-1 path passes through the LPF for
IF trap, is mixed with the SLO1 (12.495MHz to 32.195MHz)
in the quad-balanced 1st mixer (Q351 to Q354), and is
then converted to the 1st IF (11.374MHz). The 1st IF signal
passes through the 2-pole MCF(XF351) as a branch circuit
to the scope unit (X42-343 A/10) and is applied to the 2nd IF
amplifi er 1 (Q481).
The SRX-2 path signal passes through the LPF for IF
trap, is mixed with the SLO1 (73.120 to 133.095MHz) in the
quad-balanced 1st mixer (Q401 to Q404), and is then con-
verted to the 1st IF (73.095MHz). The 1st IF signal passes
through the 2-pole MCF (XF401) as a branch circuit to the
scope unit (X42-343 A/10) and is amplifi ed by approximately
12 dB by the 1st IF amplifi er (Q408: negative feedback with
transformer type).
The amplifi ed signal is mixed with the SLO2 (62.4MHz)
in the 2nd mixer (D405 and D406) and is converted to the
2nd IF (10.695MHz), and is applied to the 2nd IF amplifi er 1
(Q481).
The 2nd mixer is a passive type that uses a diode, and is
a bilateral circuit that performs the frequency conversion of
received and transmitted signals.
Fig. 17 From the sub preamplifi er (Q219) to the 2nd IF frequency (10.695MHz/11.374MHz)
From
Sub PRE AMP
SRX-2
LPF
~60MHz
Q401~404
Sub RX 1st Mixer2
Q351~354
Sub RX 1st Mixer1
Q355, 356
SLO1 AMP1
MCF
Q405, 406
SLO1 AMP2
MCF
TX
XF351
11.374MHz
XF401
73.095MHz
Scope unit
11.374MHz 73.095MHz
LPF+
11.374M NOTCH
13.174~32.195MHz
73.125~133.095MHz
SLO1
TX
Q408
Sub 1st IF AMP
D405,406
Sub 2nd Mixer
Q410
SLO2 AMP
SLO2
62.4MHz
TX
11.374MHz
10.695MHz
To
Sub 2nd IF AMP1
(Q481)
SRX-1
DIV.
DIV.

Kenwood TS-990S Specifications

General

Receiver Type	Triple Conversion Superheterodyne
Antenna Tuner	Built-in automatic antenna tuner
DSP	Yes
IF DSP	Yes
Modes	SSB, CW, AM, FM
Display	7-inch TFT color LCD
Weight	25 kg (55.1 lbs)
Antenna Connectors	SO-239
Power Supply	13.8V DC