Icom Ic-r2 Communications Reciever Service Manual

SERVICE
MANUAL
COMMUNICATIONS RECEIVER 

INTRODUCTION
DANGER
ORDERING  PARTS
REPAIR  NOTES
This service manual describes the latest service information
for the 
IC-R2at the time of publication.
NEVERconnect the receiver to an AC outlet or to a DC
power supply that uses more than 3.5 V. Such a connection
could cause a fire hazard and/or electric.
DO NOTexpose the receiver to rain, snow or any liquids.
DO NOTreverse the polarities of the power supply when
connecting the receiver.
DO NOTapply an RF signal of more than 20 dBm (100mW)
to the antenna...

SECTION 1 SPECIFICATIONS
SECTION 2 INSIDE VIEWS
SECTION 3 DISASSEMBLY INSTRUCTIONS
SECTION 4 CIRCUIT DESCRIPTION
4-1 RECEIVER CIRCUITS  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1
4-2 PLL CIRCUITS  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3
4-3 POWER SUPPLY CIRCUITS  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....

SECTION 1 SPECIFICATIONS
1 - 1
MGENERAL
• Frequency range :
• Mode : FM, WFM, AM
• No. of memory channel : 450 channel 
• Frequency stability : ±6 ppm max. 
(–10˚C to +60˚)
• Tuning steps : 5, 6.25, 10, 12.5, 15, 20,
25, 30, 50, and 100 kHz
• Anntena Impedance : 50 ½
• Power supply requirement : 2 
´ AA(R6) Ni-Cd or alka-
line cell
• Polarity : Negative ground
• Frequency resolution : 5 kHz, 6.25 kHz
• Current drain (at 3.0 V) : 
Rated audio 170 mA typical
Standby 100 mA typical
Power saved 41 mA...

SECTION 2 INSIDE VIEWS
•LOGIC UNIT
2 - 1
•RF UNIT
AF power amplifier
(IC15: TA31056F)
AF mute switch
(Q37: 2SJ144)
AF filter
(Q30: XP6501)
+3.2 regurater
(IC4: S-81332H)
2nd mixer
(IC10: µPC2757T)
IF amplifer
(Q5: 2SC5231)
FM IF IC
(IC2: TA31136FN)
PLL circuit
PLL IC
(IC3: µPD3140GS)
PLL reference 
oscillator
(X1: CR593 19.200MHz)
VCO circuit
1st mixer
(IC1: µPC2757T)
BOTTOM VIEW TOP VIEW 

SECTION 3 DISASSEMBLY INSTRUCTIONS
3 - 1
•REMOVING THE REAR PANEL
1Unscrew 2 screws, A.2Remove the rear panel in the direction of the arrow.
•REMOVING THE RF UNIT
1Unscrew 1 screw, B.2Remove 1 knob, c.
Unscrew 2 nuts, 
Dand E.
3Unsolder 5 points, F, and then remove the RF unit.
•REMOVING THE LOGIC UNIT
1Unscrew 2 screws, G.2Unsolder 2 points, H, and then remove the LOGIC unit.
ARear panel
B
E
DCRF unit
F
H
G
LOGIC unit 

SECTION 4 CIRCUIT DESCRIPTION
4 - 1
4-1 RECEIVER CIRCUITS
4-1-1 ANTENNA SWITCHING CIRCUIT (RF UNIT)
The RF signals from the antenna connector pass through
the limitter (D68) and an attenuator (D69). The signals are
then applied to the RF circuit the antenna switching circuit
(D13, D73, D75) which suppress out-of-band signals.
4-1-2 RF CIRCUIT (RF UNIT)
The RF circuit amplifies the received signals within the
range of frequency coverage and filters out-of-band signals.
(1) 0.495 MHz–29.999 MHz
RF signals...

4 - 2
IC2 contains the 3rd mixer, limiter amplifier, quadrature
detector and S-meter detector, etc. A frequency from the
PLL reference oscillator is used for the 3rd LO signal (19.20
MHz).
(1) FM mode
The 3rd IF signal is output from FM IF IC (IC2, pin 3) and
passes through the ceramic bandpass filter (FI2). The fil-
tered signal is fed back and amplified at the limiter amplifier
section (pin 5), then demodulated AF signals at the quadra-
ture detector section (pins 10, 11) and detector coil (L21).
The...

4 - 3
• TONE SQUELCH
The tone squelch circuit detects AF signals and opens the
squelch only when receiving a signal containing a matching
subaudible tone (CTCSS). When tone squelch is in use, and
a signal with a mismatched or no subaudible tone is
received, the tone squelch circuit mutes the AF signals even
when noise squelch is open.
A portion of the AF signals from the FM IF IC (IC2, pin 9)
passes through the low-pass filter (LOGIC unit; IC9) via the
“WFMS” line to remove AF (voice) signals and is...

4 - 4
LINE
BATT
VP
R3V
+3S
+3V
DESCRIPTION
The voltage from the attached battery.
Common 13 V converted from BATT line by the
DC-DC convertors (IC10 and D3, D5, D15). The
output voltage is applied to the PLL circuit (RF
unit).
Receive 3V controlled by the R3V regulator cir-
cuit (Q4) using the “RX” signal from CPU (IC11).
Common 3V converted by the +3S regulator cir-
cuit (Q3, Q39) using the “+3SC” signal from CPU
(IC11).
Common 3V converted by the +3V regulator cir-
cuit (Q6) using the “POWERC” signal...