Panasonic RF-2800LBS Manual

ORDER No. RD8003-T1030
Technical Information
Radio
Poriable
ado
RF-2800LBS
RF-2900LBS
Subject: Frequency Counter Circuit
Table of Contents
P< Outline 223.028 ahat on ahecs ge added ele agp emoe awaits page 2
il, Block Diagram ... 0... cece eee page 3
ill, Preset Selector Circuit ............0.0.00.00 00.0 c eee eee page 4
As EM Bands scsi. t.ccccissed ia ian baeeoned deals ees page 5
Be AM Band 8 ste ice tie x Rateiciati se es Sota Dacia page 5
iV. Counter Signal Circuit........... 0.0022, page 5
V. Signal Selector Circuit ........000.0.0 00.0. eee page 6
Aes PM Band ssid thse see ies oar sdaagt Sobel Pod hi weches Gl tee de, page 6
Bs ‘AM Bands. felts ote ilar ot ee dae ne beeen keels page 6
tae o Matsushita Electric Trading Co., Ltd.
Panasonic P.O. Box 288, Central Osaka, Japan

RF-2800/RF-2900 Frequency Counter Circuit
4
|. Outline:
The RF-2800/RF-2900 displays the frequency of the received broadcast by counting the frequency of the local
oscillator and scaling accordingly. Figure 1 is a block diagram for the receiver. The following relationships exist
between the reception frequency (fs), the local oscillator frequency (fo), the intermediate frequency (fi) and the
display frequency (fo).
(A) fs+fi=fo...(1)
. (B) fo=fs=fotfi... (2)
LOCAL OSC
., CONVERSION
COMMAND
DEVICE
Fig. 1
With reference to figure 1, for example
Reception frequency (fs)=10 MHz
Intermediate frequency (fi)=455 kHz
Under these conditions, the local oscillator frequency (fo) must be, according to formula (1), 10.455 MHz (called
“upper local oscillation’’) or 9.545 MHz (called “lower local oscillation’’). Thus, if 10.455 MHz is used as the local
oscillator signal:
Display frequency (fo)= 10.455 (fo) — 0.455 (f)= 10 MHz (fs)...... (3)
Therefore, the display frequency is equivalent to the reception frequency.
The subtraction of the 0.455 MHz (fi) is accomplished by the conversion command device to the counter.
if the unit were designed to use the lower local oscillator frequency, a signal (preset frequency= + 0.455 MHz)
would be applied to the counter in order to add 0.455 MHz.
At the same time, in models which use different frequency, such as 2 MHz, for the intermediate frequency (fi), a
conversion signal is applied to the counter in order to add (or subtract) 2 MHz, so that the reception frequency will
be correctly displayed.
In short, the conversion signal must be equal to +fi. -

ll. Block Diagram
Figure 2 is a chart of the reception frequency, local oscillator frequency and intermediate frequency for each
band.
Intermediate Local Osc.
Frequency (MHz) Frequency (MHz) Frequency (MHz)
10.7 98.2 ~ 118.7
LW 0.150 ~ 0.410 0.605 ~ 0.865
8.0 ~ 16.0 2. | 10.0
16.0 ~ 30.0 2 | 18.0
Fig. 2
Because, the upper local oscillator frequency is used the conversion signal is subtracted from the counter circuit
for each band.
As can be understood from the table in figure 2, an intermediate frequency of 10.7 MHz is used for the FM band.
Because the upper local oscillator frequency is used, the reception frequency is displayed after 10.7 MHz has
been subtracted from the local oscillator frequency.
For the LW, MW bands, 455 kHz is subtracted from the local oscillator frequency.
For the SW bands, 2 MHz is subtracted from the local oscillator frequency.
Figures 3 and 4 are block diagrams which include the RF, Local Oscillator, IF and Counter circuits.
The subtraction is accomplished through logic signals applied to pins 3, 4, 5 and 6 of IC902.
ANT
F
RF AMP IF ; \F AMP ' IF AMP
LOCAL OSC
C101 Q103
3 1101
COUNTER COUNTER
BUFFER
e164
PRE-AMP
(3)
River
AM
CIRCUIT
Q901,0902
1C901
0000
FM Circuit
0
O
©
is
COUNTER
O AMP (2) Ree DISPLAY
O si7 Q907 1c902
2)
Swt/Swe/Sw3
TUNING CIRCUIT
L410,L109, L108
CIRCUIT
£102
EP
NOTE:
1.8902 terminal Nos. 3.4.5,6:for Preset
L. condition in terminals 3,4..5 and-6):—10.7MHz
2. $1:Band Selector
FMLW/MW/SW1/SW2/SW3 Fi ig. 3 FM Section Block Diagram
shown at FM position

C101
FM
O
==
©
.
SW
2nd
MIX
2)
T102 —™ 1102 15
O RF AMP
Q108
: SWITCHING
Ei Q105, Q106
000000
“oO l
O TUNING
O CIRCUIT
a
COUNTER COUNTER COUNTER COUNTER
PRE-AMP G} oriver (8) AMP @} circuit DISPLAY
Nore
Q901,0902
Ic901
a908
1C902
$1
Band
Selector
o
FM/LW/MW/SW1/SW2/SW3 (Q)@&E)
shown in MW position.
OSC COILS
L118,L117,
L1t6,0115.
L114
IC902 terminals '3)..4),.5':and 6, For Preset
Fig.4 LW/MW/SW Section Block Diagram
lll. Preset Selector Circuit
Figure 5 shows the relationship between the preset terminals (3, 4, 5 and 6) of IC902 and the preset frequency.
Preset terminal
Band
|
Preset Frequency
(MHz)
Fig. 5

Figure 6 shows the preset selector circuitry.
COUNTER
CIRCUIT
IC902
CONNECTER
CP2-CS2
$1-9 :
O
LW MW SW1SW2SW3
a or oy
DISPLAY
Preset
terminal
A. For FM:
(a) Terminal 6 of IC902 becomes an ‘'L” level. (through connectors Pin 1—-L120—Pin 7-+GRND)
(b) Terminal 5 of IC902 becomes an ‘'L" level. (through S1—9 .—Connector Pin 2.)
(c) Terminal 4 of C902 becomes an “'L”’ level. (through S1—-9—» D106—+Connector Pin 3)
(d) Terminal 3 of IC902 is set at an ‘‘L”’ level. (through S1—9->Connector Pin 4)
As a result, (refer to the table in figure 5) the counter circuit subtracts 10.7 MHz from the local oscillator
frequency (the input signal), and the result is displayed as the reception frequency.
B. Inthe same way, for the LW, MW and SW bands the condition of each preset terminal is changed by the band
selector (S1—9) consenquently, the preset frequency shown in the table in figure 5 is obtained, and the correct
reception frequency is displayed.
IV. Counter Signal Circuitry
Figure 7 shows the counter signal circuitry.
A.
For
each
band,
the
local
oscillator
signal
from
the
local
oscillator
circuitry
is
selected
(FM,
LW,
MW
or
SW)
by
SW-A,
and
is
supplied to
terminal 3
of
the
driver
circuit
(IC901).
B.
This
signal
is
frequency
divided
(1/8)
by
IC901,
and
is
output
from
terminal
8.
At
the
same
time,
a
signal
(frequency
divided
by 1/80)
is
output
from
terminal 9.
DRIVER CIRCUIT
C901 COUNTER CIRCUIT
IC902
Counted Frequency
from Local OSC
(9) X'tat OUT
FM: 98.2--118.7 MHz
LW: 605~865 kHz
MW: 987~2.072 kHz
Preset DISPLAY
terminal
SW1: 5.2-- 10.0 MHz
SW2: 10~18 MHz
SW3: 18~ 32 MHz

C. These two output signals are selected (by SW-B): the 1/8 frequency divided output (from terminal 8) for the
LW, MW band and SW:~SWSs bands, and the 1/80 frequency divided output (from terminal 9) for the FM band
are applied to the input terminal (terminal 2) of the counter circuit (IC902).
D. These frequencies are converted, by !C902, into the original local oscillator frequencies. Moreover,
depending upon the signal applied to the preset terminals, the necessary frequency for each band is
subtracted from the derived local oscillator frequencies and the resulting frequency is supplied to the display.
V. Signal Selector Circuitry
Figure 8 shows the signal selector circuitry for the counter.
A. For the FM band, since the band selector (S1-9) is in the ‘‘FM”’ position, the base of each transistor (Q904,
Q905 and Q906) becomes an ‘‘L”’ level, consenquently, Q904 and Q905 turn on, and Q906 turns off.
As a result, the signal from the FM band local oscillator flows as shown below, and is counted at the counter
circuitry.
FM Local osc + C902 — Q901 —» Q902 -» C908 — IC901(3) — IC901(9) + C914—» Q907 — IC902(2)
In this case instance, the local oscillator circuitry for the LW, MW and SW bands does not function (refer to
figures 3, 4 and the +B selector).
The signal (AM) from the 1/8 frequency divider is output from terminal 8 of |C901.
However, because Q905 is turned on thus shorting its collector to emitter junction, the base to emitter junction
of Q908 is also shorted, therefore, the signal current can not flow to the counter circuit.
NOTE:
é
ot
$1-8:
Band
Selector
Sw3
Se
te
a
FM/LW/MW/SW1/SW2/SW3
CLP
UP
Ail
FS.
shown
at
FM
position.
@)
+
G):
ee
»)
|
cp2
CONNECTOR
'
©
6)
O|
a
R908 DRIVER CIRCUIT
—> Q904 1c901
/8
R901
COUNTER CIRCUIT
Ic902
FM BAND C902 Q901 Q902
LOCAL OSC i) (Sh
CIRCUIT ss el
c303
AM BAND
LOCAL Osc].
CIRCUIT R907
(2) INPUT
Fig. 8
B. For the LW, MW and SW:~SWs bands, Si-9 is open, the base (Q904, Q905 and Q906) become an ‘‘H” level,
consenquently Q904 and Q905 turn off, and Q906 turns on.
As a result, transistor Q907 turns off (base to emitter junction shorted by Q906) which results in Q901 turning
off. Therefore, the signal from the AM local oscillator circuit flows as shown below, and is supplied to the
counter circuitry (IC902).
AM local osc — C903 — Q902 — C908 — 1C901(3) — 1C901(8) — C912 —. Q908 —. IC902(2)
In this case, the local oscillator circuitry for the FM band does not function.
The
above
is
a
description
of
the
operation
of
the
frequency
counter
circuitry
for
models
RF-2800/RF-2900.
The frequency
counter circuitry
for other
models is
similar.
Refer to
RF-4900
Technical
Information
(Order
No.
RD8002-T
1028),
because
the
counter
circuitry
for
models RF-2800/RF-2900
uses
the same
LSI
as
model
RF-4900.
|
RD
® x!
Printed
in
Japa

EM/LVW/MW/SW
6-BAND PORTABLE RADIO
Mi SPECIFICATIONS
Frequency Range: FM
LW
MW
SW:
SW2
SWs3
Intermediate FM
87.5~108 MHz
150~410 kHz (2000~731m)
525~1610 kHz (571~186m)
3.2~8 MHz (93.8-~37.5m)
8~16 MHz (37.5~18.7m)
16~30 MHz (18.7~10m)
10.7 MHz
Frequency: AM (LW, MW & SW) 455 kHz
Sensitivity : FM
LW
MW
SW;
SW2
SWs
2.5uV (S/N 26 dB),
2uV (3 dB down limitter sens.)
704V/m (S/N 6 dB), 600zV/m (S/N 26 dB)
302V/m (S/N 6 dB), 400“V/m (S/N 26 dB)
1.8uV (S/N 6 dB), 192V (S/N 26 dB)
0.82V (S/N 6 dB), 92V (S/N 26 dB)
1.24V (S/N 6 dB), 134V (S/N 26 dB)
Power Output: 3W DC Maximum
National Panasonic
Power Source:
Power Consumption:
Speaker:
Dimensions:
Weight:
Impedance:
ORDER NO. RD7803-1549
ervice Manual
Radio
RF-2800LBS
AC 110~125V/220—~240V 50-60 Hz or
9V (Six ‘‘D” Size Flashlight Batteries)
(National UM-1 or equivalent)
11W (AC Only)
10 cm (4’’) PM Dynamic Speaker
381(Wide) x 246(High) x 120(Deep)mm
(15° x 942"' x 43")
2.3 kg. (8 Ib. 10 oz.) without batteries
Speaker 2.0.0... .....ccccceccccue suas BQ
Earphone Jack..................... ixe)
Multiplex Out Jack ......... 10k. (40mV)
FM Antenna Terminal ......... 752
Phono Jack.................. 500k (50mV)
Recording Out Jack ...... 80ka2 | 100mvV)
Specifications are subject to change without notice for further improvement.
Matsushita Electric Trading Co., Ltd.
P.O. Box 288, Central Osaka, Japan

M@ TO REMOVE CABINET COVER
1.
Remove the battery cover.
2. Remove the six (6) screws (nos. 1~6) for the cabinet cover,
tf
as shown in fig. 1.
. Remove the cabinet cover.
. Pull out sockets from PC board.
. To reassemble, reverse the above procedure.
M@ TO REMOVE PC BOARD (IF, RF Circuit)
1.
Onno
7.
8.
Remove the cabinet cover. (Refer to cabinet cover removal
instruction.)
. Remove the band knob. (To remove the knob, wind a cord
around the control and pull it outward.)
. Turn the tuning knob fully counter-clockwise.
. Pull out the sockets from PC board.
. Unsolder lead from PC board.
Remove the eight (8) screws (nos. 1~8) for the PC board,
as shown in fig. 2.
Remove the PC board.
To reassemble, reverse the above procedure and note the
followings.
Notes
1.
2.
Turn the tuning knob fully counter-clockwise.
Turn the tuning capacitor shaft fully counter-clockwise.
M@ TO REMOVE FREQUENCY COUNTER
1.
o
Remove the PC board (IF, RF circuit). (Refer to PC board
removal instruction.)
. Remove the two (2) screws (nos. 1 & 2) for-the frequency
counter, as shown in fig. 3.
. Remove the frequency counter.
To reassemble, reverse the above procedure.
@ TO REMOVE PC BOARD (Frequency Counter)
1.
Remove the frequency counter. (Refer to frequency counter
removal instruction.)
2. Remove the four (4) screws (nos. 1~4) for the frequency
counter cover, as shown in fig. 4.
3. Remove the two (2) screws (nos. 1 & 2) for the PC board, as
shown in fig. 5.
4. Remove the PC board.
5. To reassemble, reverse the above procedure.
Screw No.1
(XTN3+6F)
Screw No.2
XTN3-+6F)
Fig. 5
[2] rr-2800LBS
Screw No.1(CA17) Screw No.2(CAi7) Screw No.3 (CA17)
Screw No.4 (CA) Screw No.5 (CAt7) ~~ Screw No.6 (CAi7)
Fig. 1
Screw No.1 Screw No.2 Screw No.3 Screw No.4
(XTN3-+6F) (XTN3+6F)
(XTW3-++10F) (XTW3+10F)
a
a
Screw No.5 Screw No.6 Screw No.7 Screw No.8
(XTW3-++10F) (XTW3-+10F) (XTW3+10F) — (XTW3-++-10F)
Fig. 2
Screw No. 1 Screw No.2 Screw No.3 Screw No.4
(XTW3+10F) (XTW3+10F) (XTW3-++10F) (XTW3+-10F)
acre
Screw No.5 Screw No.6 Screw No.7 Screw No.8
(XTW3+10F) (XTW3-+-10F) (XTW3+10F) — (XTW3-++10F)
Fig. 3
Screw No.1 Screw No.3
(XTN3+6F) XTN3+6F)
: Screw No.4
Screw No.2 XTN3-+-6F)
(XTN3-+6F)
Fig. 4

M@ TO REMOVE DIAL SCALE CHASSIS
1.
Remove the PC board (IF, RF circuit). (Refer to PC board
removal instruction.)
Remove the tuning knob.
Remove the six (6) screws (nos. 3~8) for the dial scale
chassis, as shown in fig. 3.
Remove the dial scale chassis.
M TO REMOVE DIAL MECHANISM
1.
Remove the dial scale chassis. (Refer to dial scale removal
instruction.)
2. Remove the dial belt, as shown in fig. 7.
3. Remove the two (2) screws (nos. 1 & 2) for the dial mech-
anism, as shown in fig. 6.
4. To reassemble, reverse the above procedure and note the
followings.
Notes
1. Turn the tuning shaft fully counter-clockwise.
2. Set the dial scale at the position, as shown in fig. 7.
3. Attach the dial belt.
4. Refer to dial scale removal instruction.
@ TO REMOVE DIAL SCALE
1.
Remove the dial scale chassis. (Refer to the dial scale
chassis removal instruction.)
2. Remove the one (1) screw for the dial scale spring, as
shown in fig. 7.
3. Remove the dial scale.
4. To reassemble, reverse the above procedure and note the
followings.
Notes:
1. Loosen the two (2) screws (nos. 1 & 2) for the dial scale
gear, as shown in fig. 8.
2. Set the catch of dial scale gear to the start point of dial
scale, as shown in fig. 9.
3. Turn the tuning shaft fully counter-clockwise.
4. After mounting the PC board (IF, RF circuit), turn the dial
scale by pushing the catch of dial scale and set the start
point of dial scale to the catch of cabinet, as shown in
fig. 10.
5. Tighten the two (2) screws (nos. 1 & 2) for the dial scale
gear, as shown in fig. 10.
Screw No.1
Catch of Cabinet Start Ponint (XXAR3H6S)
Fi
Bie S. se
Screw No.2
(XXAR3H6S)
Fig. 10
Seiew No.1 ‘a Sorew No.2
(XTW3-++10F) (XTW3+10F)
Fig. 6
0d.
Screw
(XTN23-+6C) : a
ae in OS
Dial
Belt
©
Sg
ae’
ge .
5 RSGBIBS
eas
Fig. 7
Screw No.1 Screw No.2
(XXAR3H6S) (XXAR3H6S)
Kw Kw | qed
-| SWI | SW2' Syvads
2 My
Catch Start Point
Fig. 9
RF-2810L-BS [3]

M@ TO REMOVE PC BOARD (AF Circuit)
Srey : een ( Subp
: e XTW3-+10F XTW3-+10F,
1. Remove the dial scale chassis. (Refer to the dial scale ( )
chassis removal instruction.)
2. Remove the six (6) knobs for the RADIO, LIGHT, BAND
WIDTH, VOLUME, BASS and TREBLE.
3. Remove the five (5) screws (nos. 2, 3, 5, 6 & 7) for the PC
board, as shown in fig. 11.
. Unsoider lead from PC board.
. Pull out sockets from PC board.
. Remove the PC board. :
. To reassemble, reverse the above procedure.
NOOO
Screw No.4 “Screw No.5 Screw No.6 Screw No.7
(XTW3-++H10F) (XTW3-+10F) (XTW3-F10F) (XTW3-+10F)
@ TO REMOVE PC BOARD (Control Circuit)
1. Remove the dial scale chassis. (Refer to the dial scale Fig. 11
chassis removal instruction.)
2. Remove the three (3) knobs for the SW CAL, RF GAIN and Indicator
PITCH. (To remove those control knobs wind a cord around
the control and pull it outward.)
3. Remove the two (2) screws (nos. 1 & 4) for the PC board.
. Remove the PC board.
5. To reassemble, reverse the above procedure.
>
@ TO REMOVE INDICATOR
1. Remove the PC board (AF circuit).
(Refer to PC board removal instruction.)
2. Unsolder the terminal of indicator, as shown in fig. 12.
3. Remove the indicator.
4. To reassemble, reverse the above procedure.
M@ HOW TO REPLACE CHIP
1. Remove solder for chip completely. Cc :
: ; Pe | Color | Original Parts Name Service Parts Name
2. Remove chip by nippers, as shown in fig. 13. hie Resistor Garbon Fegictor
3. Use tube for service parts as shown in fig. 14 and solder
)
service
parts
according
to
following
table.
(please
refer
Blue
Shi
Sapa
rerarie
Capecner
to
Circuit
Board
Wiring
View
for
the
value
of
resistor
and
capacitor).
Ceramic
Capacitor
Carbon
Resistor
Fig. 13 Fig. 14
[4] pr-2800LBs