HCD-RG121, MHC-RG121 - Sony Audio Service Manual (repair manual)

AEP Model

UK Model

E Model

Australian Model

2004D1679-1
© 2004.04

• HCD-RG121 is the tuner, deck, CD and

amplifier section in MHC-RG121.

DIN power output (rated): 50 + 50 watts (6 ohms at 

1 kHz, DIN)

Continuous RMS power output (reference):

65 + 65 watts (6 ohms at 
1 kHz, 10% THD)

Music power output (reference):

130 + 130 watts (6 ohms at 
1 kHz, 10% THD)

The following measured at AC 120, 127, 220, 240 V 
50/60 Hz
DIN power output (rated): 50 + 50 watts (6 ohms at 

1 kHz, DIN)

Continuous RMS power output (reference):

60 + 60 watts (6 ohms at 
1 kHz, 10% THD)

System

Compact disc and digital 
audio system

Laser

Semiconductor laser 
(

λ=780 nm)

Emission duration: 
continuous

Frequency response

2 Hz – 20 kHz (

±0.5 dB)

Wavelength

780 – 790 nm

Signal-to-noise ratio

More than 90 dB

Dynamic range

More than 90 dB

FM stereo, FM/AM superheterodyne tuner

FM tuner section

Tuning range
North American model:

87.5 – 108.0 MHz 
(100-kHz step)

Russian model:

65.0 – 74.0 MHz
(There is no stereo effect. 
10-kHz step)
87.5 – 108.0 MHz 
(50-kHz step)

Other models:

87.5 – 108.0 MHz
(50-kHz step)

Antenna

FM lead antenna

Antenna terminals

75 ohms unbalanced

Intermediate frequency

10.7 MHz

Recording system

4-track 2-channel, stereo

Frequency response

50 – 13,000 Hz (

±3 dB), 

using Sony TYPE I 
cassettes

Model Name Using Similar Mechanism

New

CD

CD Mechanism Type

CDM74-K6BD80

Section

Optical Pick-up Name

KSM-213DCP/Z-NP

Tape deck

Model Name Using Similar Mechanism

New

Section

Tape Transport Mechanism Type

CWM43FF-05

– Continued on next page –

2

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Power requirements
European and Russian models:

110 watts
0.25 watts (at the Power 
Saving Mode)

Other models:

110 watts

Dimensions (w/h/d) incl. projecting parts and controls 
Amplifier/Tuner/Tape/CD section:

Approx. 280 

× 327 × 

425 mm

Mass 
European and Russian models:

Approx. 8.5 kg

Other models:

Design and specifications are subject to change 
without notice.

Approx. 8.5 kg

AM tuner section

Tuning range
Pan-American models:

530 – 1,710 kHz 
(with the tuning interval 
set at 10 kHz)
531 – 1,710 kHz 
(with the tuning interval 
set at 9 kHz)

European, Russian and Saudi Arabian models:

531 – 1,602 kHz (with the 
tuning interval set at 
9 kHz)

Other models:

530 – 1,710 kHz 
(with the tuning interval 
set at 10 kHz)
531 – 1,602 kHz 
(with the tuning interval 
set at 9 kHz)

Antenna

AM loop antenna

Antenna terminals

External antenna terminal

Intermediate frequency

450 kHz 

There is a disc lock function for the disc theft prevention for a
demonstration at a shop front in this machine.
Procedue:
1. Press the  ?/1  button to turn the set on.
2. Press two buttons of  x  and  Z (EJECT)  simultaneously for

five seconds.

3. The message “LOCKED” is displayed and the tray is locked.

(Even if exiting from this mode, the tray is still locked.)

4. Press two buttons of  x  and  Z (EJECT)  simultaneously for

five seconds again.

5. The message “UNLOCKED” is displayed and the tray is

unlocked.

6. To exit from this mode, press the  ?/1  button to turn the set

off.

This appliance is classified as a CLASS 1 LASER product. The
CLASS 1 LASER PRODUCT MARKING is located on the rear
exterior.

• Never reuse a disconnected chip component.
• Notice that the minus side of a tantalum capacitor may be

damaged by heat.

• Keep the temperature of soldering iron around 270˚C

during repairing.

• Do not touch the soldering iron on the same conductor of the

circuit board (within 3 times).

• Be careful not to apply force on the conductor when soldering

or unsoldering.

The laser diode in the optical pick-up block may suffer electrostatic
break-down because of the potential difference generated by the
charged electrostatic load, etc. on clothing and the human body.
During repair, pay attention to electrostatic break-down and also
use the procedure in the printed matter which is included in the
repair parts.
The flexible board is easily damaged and should be handled with
care.

The laser beam on this model is concentrated so as to be focused on
the disc reflective surface by the objective lens in the optical pick-
up block. Therefore, when checking the laser diode emission,
observe from more than 30 cm away from the objective lens.

Use of controls or adjustments or performance of procedures
other than those specified herein may result in hazardous radiation
exposure.

Laser component in this product is capable
of emitting radiation exceeding the limit for
Class 1.

3

...............................................

4

...................................................................

6

3-1.

Cover (Top) ...........................................................

9

3-2.

CD Door ................................................................

9

3-3.

Front Panel Section ............................................... 10

3-4.

CD Mechanism Deck (CDM74-K6BD80) ............ 10

3-5.

Tape Mechanism Deck, GAME JACK Board ....... 11

3-6.

PANEL Board ........................................................ 11

3-7.

Back Panel Section, SUB-TRANS Board ............. 12

3-8.

Power Transformer ................................................ 12

3-9.

MAIN Board ......................................................... 13

3-10. AMP Board ........................................................... 13
3-11. BD80A Board ........................................................ 14
3-12. CONNECT Board ................................................. 14
3-13. DRIVER Board, SW Board .................................. 15
3-14. Optical PICK-UP (KSM-213DCP/Z-NP) ............. 15
3-15. SENSOR Board ..................................................... 16
3-16. MOTOR (TB) Board ............................................. 16
3-17. MOTOR (LD) Board ............................................. 17

............................................................... 18

5-1.

Block Diagram – PANEL Section – ...................... 22

5-2.

Block Diagrams – MAIN Section – ...................... 23

5-3.

Block Diagrams – BD/DRIVER Section – ........... 24

5-4.

Printed Wiring Board – BD80A Section – ............ 25

5-5.

Schematic Diagram – BD80A Section – ............... 26

5-6.

Printed Wiring Board
– CD MECHANISM Section – ............................. 27

5-7.

Schematic Diagram
– CD MECHANISM Section – ............................. 28

5-8.

Printed Wiring Board – MAIN Section – .............. 29

5-9.

Schematic Diagram – MAIN Section (1/2) – ........ 30

5-10. Schematic Diagram – MAIN Section (2/2) – ........ 31
5-11. Printed Wiring Board

– PANEL COMB Section – ................................... 32

5-12. Schematic Diagram

– PANEL COMB Section – ................................... 33

5-13. Printed Wiring Board – PANEL Section – ............ 34
5-14. Schematic – PANEL Section (1/2) – ..................... 35
5-15. Schematic – PANEL Section (2/2) – ..................... 36
5-16. Printed Wiring Board – TRANS Section – ........... 37
5-17. Printed Wiring Board – AMP Section – ................ 38
5-18. Schematic Diagram – AMP POWER Section – .... 39
5-19. IC Pin Function Description .................................. 42

6-1.

MAIN Section ....................................................... 48

6-2.

Front Panel Section ............................................... 49

6-3.

MAIN Board Section ............................................ 50

6-4.

CD Mechanism Deck Section-1
(CDM74-K6BD80) ............................................... 51

6-5.

CD Mechanism Deck Section-2
(CDM74-K6BD80) ............................................... 52

.................................. 53

Boards requiring use of unleaded solder are printed with the lead-
free mark (LF) indicating the solder contains no lead.
(Caution: Some printed circuit boards may not come printed with
the lead free mark due to their particular size.)

Unleaded solder has the following characteristics.
•

Unleaded solder melts at a temperature about 40°C higher than
ordinary solder.
Ordinary soldering irons can be used but the iron tip has to be
applied to the solder joint for a slightly longer time.
Soldering irons using a temperature regulator should be set to
about 350°C.
Caution: The printed pattern (copper foil) may peel away if the
heated tip is applied for too long, so be careful!

•

Strong viscosity
Unleaded solder is more viscous (sticky, less prone to flow) than
ordinary solder so use caution not to let solder bridges occur
such as on IC pins, etc.

•

Usable with ordinary solder
It is best to use only unleaded solder but unleaded solder may
also be added to ordinary solder.

4

To inspect the AMP board, turn both of the front panel and the
CD mechanism deck so that the left side of the product faces
down.

front panel

CD mechanism deck

AMP board