Panasonic RF-B20L - User Manual

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ORDER

NO.

GAD8512037C2

Service

Manual

Radio

BSarit

Recoker

RF-B20L

(Black)

This

the

Service

Manual

for

the

following

areas.

[Z].

..For

all

European

areas

except

United

Kingdom.

[E]...For

United

Kingdom.

SPECIFICATIONS

Frequency

Range:

FM;

87.5~108

MHz

Power

Requirement:

Battery;

4.5

MW;

520~1610

kHz

(Three

UM-3,

“AA”

size

LW;

150~285

kHz

batteries)

SW1;

5.95~6.20

MHz

(49

(Panasonic

UM-3

equivalent)

SW2:

7.10~7.30

MHz

(41

AC;

with

optional

adaptor

RP-AC4

SWS;

9.50~9.90

MHz

(31

Power

Output:

400

(max.)

SW4;

11.65~12.05

MHz

(25

Speaker:

6.5

Dynamic

Speaker

(8Q)

SW5;

15.10~15.60

MHz

(19

Impedance:

Earphone;

8Q,

23.5

SW6;

17.55~17.90

MHz

(16

Dimensions:

[173

(W)

x92

(H)

x29

(D)]

Intermediate

Frequency:

FM;

10.7

MHz

Weight:

320

without

batteries

(MW,

LW,

SW);

455

kHz

Sensitivity:

462

kHz

(For

U.K.)

FM;

2yV/50

output

(—3

aB,

Limit

Sens)

MW;

100

pV/m/50

output

LW;

126

uV/m/50

output

SW1;

1.8

uV/50

output

SW2;

1.3

yV/50

output

SW3;

1.4

uV/50

output

SW4;

1.3

yV/50

output

SW5;

1.3

yV/50

output

SW6;

1.4

uV/50

output

Design

and

specifications

are

subject

change

without

notice.

Panasonic

Matsushita

Electric

Trading

Co.,

Lt.

Need help?

Do you have a question about the Panasonic RF-B20L and is the answer not in the manual?

The Panasonic RF-B20L is a versatile 9-band receiver, offering a wide range of listening options across FM, MW, LW, and six Shortwave (SW) bands. Designed for portability and ease of use, this black-colored radio is suitable for various regions, with specific configurations for European areas (excluding the United Kingdom) and the United Kingdom.

Function Description:

The RF-B20L primarily functions as a multi-band radio receiver. It allows users to tune into local FM, Medium Wave (MW), and Long Wave (LW) broadcasts, as well as international Shortwave (SW) transmissions across six distinct meter bands (SW1-SW6). The receiver incorporates a double superheterodyne system for enhanced SW reception, aiming to provide stable and clear audio across its broad frequency range.

Key controls include a Power Off Button, a Hold Switch to prevent accidental operation, and dedicated Band Select Buttons for FM, MW, LW, and SW. For Shortwave, a SW1-6 Band Selector allows for precise selection of the desired meter band, indicated by a SW1-6 Band Index Indicator. Tuning is managed via a Tuning Control, complemented by a Tuning Indicator that illuminates when a station is correctly tuned. Audio output is controlled by a Volume Control and can be adjusted for tonal quality using a Tone Control, offering bass accentuation in the "LOW" position and treble accentuation in the "HIGH" position.

The device is equipped with both a telescopic antenna for FM and SW reception and a sensitive ferrite core antenna for MW/LW, ensuring optimal signal capture across different bands. For private listening, an Earphone Jack (Ø3.5, 8Ω) is provided, which automatically disconnects the internal speaker when in use. Power can be supplied by batteries or an optional AC adaptor (RP-AC4) via the DC Input Jack (DC IN 4.5V). A DX-LOCAL Sensitivity Selector (SENS) allows users to optimize reception for MW, LW, and SW by switching between "DX" for normal reception and "LOCAL" to mitigate interference from powerful stations or impaired signals. This selector does not affect FM reception.

Important Technical Specifications:

Frequency Range:
- FM: 87.5~108 MHz
- MW: 520~1610 kHz
- LW: 150~285 kHz
- SW1: 5.95~6.20 MHz (49 m)
- SW2: 7.10~7.30 MHz (41 m)
- SW3: 9.50~9.90 MHz (31 m)
- SW4: 11.65~12.05 MHz (25 m)
- SW5: 15.10~15.60 MHz (19 m)
- SW6: 17.55~17.90 MHz (16 m)
Intermediate Frequency:
- FM: 10.7 MHz
- AM (MW, LW, SW): 455 kHz (462 kHz for U.K.)
Sensitivity:
- FM: 2µV/50 mW output (-3 dB, Limit Sens)
- MW: 100 µV/m/50 mW output
- LW: 126 µV/m/50 mW output
- SW1: 1.8 µV/50 mW output
- SW2: 1.3 µV/50 mW output
- SW3: 1.4 µV/50 mW output
- SW4: 1.3 µV/50 mW output
- SW5: 1.3 µV/50 mW output
- SW6: 1.4 µV/50 mW output
Power Requirement:
- Battery: 4.5 V (Three UM-3, "AA" size batteries, Panasonic UM-3 or equivalent)
- AC: With optional AC adaptor RP-AC4
Power Output: 400 mW (max.)
Speaker: 6.5 cm PM Dynamic Speaker (8Ω)
Earphone Impedance: 8Ω, Ø3.5
Dimensions: [173 (W)×92 (H)×29 (D)] mm
Weight: 320 g without batteries

Usage Features:

The RF-B20L emphasizes user-friendly operation. The Hold Switch is a notable feature, allowing users to lock the current settings and prevent accidental changes or power-offs, which is particularly useful when carrying the unit or to conserve battery life. When the Hold Switch is engaged, the Band Select Buttons and Power Off Button become inoperative.

Antenna adjustment is crucial for optimal reception. For FM, the telescopic antenna should be fully extended and angled. For MW/LW, the internal ferrite core antenna requires orienting the entire set in the direction that yields the best results, as it is directional. For SW1-6, the telescopic antenna should be fully extended and kept vertical. A specific caution is provided for adjusting the telescopic antenna: the base must be pulled free until a click is heard before extending the remaining sections. When folding, the base should be pushed back first, followed by the thicker antenna elements.

The Tuning Indicator serves as a visual aid, lighting up when a station is correctly tuned. However, users are advised that the indicator may not light up with weak signals or low battery power, even if audio is audible. It can also be falsely triggered by nearby TV receivers or fluorescent lamps. The DX-LOCAL Sensitivity Selector is a practical feature for improving reception quality in varying signal environments, though it is not applicable to FM.

Maintenance Features:

The service manual provides detailed instructions for disassembly and alignment, indicating that the device is designed for maintainability by qualified technicians.

Disassembly: Step-by-step instructions are provided for removing external components like the telescopic antenna, battery cover, rear cabinet, knobs, and internal circuit boards. Specific screw types and quantities are listed for each step. Special care is advised when removing the SW1-6 Band Switch Knob to avoid losing the steel ball and spring.
Dial Threading: Detailed instructions are given for threading the dial cord, including connecting dial drums, meshing them, winding the cord, attaching the pointer, and securing it with locking enamel paint. This ensures accurate frequency indication.
Alignment: Comprehensive alignment procedures are outlined for AM-IF, LW-RF, MW-RF, SW1-6 2nd Local OSC, SW1-6 1st IF, and FM-IF/RF. These procedures require specific signal generator settings, radio dial settings, and the use of an electronics voltmeter or scope for precise adjustments. Key alignment points include various coils (OSC, ANT), IFTs, and trimmer capacitors. Cementing antenna bobbins with wax after alignment is specified for SW1-6 2nd Local OSC.
Replacement Parts: An extensive electrical parts list and cabinet parts list are included, providing part numbers and descriptions for various components such as integrated circuits, transistors, diodes, coils, transformers, capacitors, resistors, switches, and mechanical parts. This facilitates accurate component replacement.
Circuit Board and Wiring Connection Diagram: Detailed diagrams illustrate the layout of the main circuit board and LED circuit board, including component locations and wiring connections. Test points are clearly marked to aid in troubleshooting and alignment. Instructions for replacing chip parts are also provided, emphasizing careful handling with tweezers and soldering irons to prevent damage to the circuit board plating.

Overall, the Panasonic RF-B20L is a robust and feature-rich multi-band receiver, designed with both user convenience and technical serviceability in mind. Its comprehensive specifications and detailed service manual underscore its quality and potential for long-term use.