HCD-EC68P, HCD-EC78P, MHC-EC68PI, MHC-EC78PI - Sony Audio Service Manual (repair manual)

2009A05-1

© 

2009.01

•  HCD-EC68P is the amplifi er, CD player and 

tuner section in MHC-EC68Pi.

•  HCD-EC78P is the amplifi er, CD player and 

tuner section in MHC-EC78Pi.

Photo : HCD-EC78P

Model Name Using Similar Mechanism

CDM77B-K6BD90-WOD

NEW

CDM88A-K6BD90-WOD

HCD-EC68

Mechanism Type

Except EC78P (UK)

CDM77B-K6BD90-WOD

EC78P (UK)

CDM88A-K6BD90-WOD

Base Unit Name

BU-K6BD90-WOD

Optical Pick-up Block Name

KSM-213DCP

AUDIO POWER SPECIFICATIONS
POWER OUTPUT AND TOTAL HARMONIC DISTORTION:

Low channel
With 8 ohm loads, both channels driven, from 120 – 10,000 Hz;
60 watts per channel minimum RMS power, with no more than
0.7% total harmonic distortion from 250 milliwatts to rated output.
High channel
With 8 ohm loads, both channels driven, from 2,000 – 13,000 Hz; 
60 watts per channel minimum RMS power, with no more than
0.7% total harmonic distortion from 250 milliwatts to rated output.

AUDIO POWER SPECIFICATIONS
POWER OUTPUT AND TOTAL HARMONIC DISTORTION:

With 6 ohm loads, both channels driven, from 120 – 10,000 Hz;
40 watts per channel minimum RMS power, with no more than
0.7% total harmonic distortion from 250 milliwatts to rated output.

RMS output power (reference):

Low channel
95 W + 95 W (per channel at 8 Ω, 1 kHz, 10% THD)
High channel
95 W + 95 W (per channel at 8 Ω, 8 kHz, 10% THD)

RMS output power (reference):

70 W + 70 W (per channel at 6 Ω, 1 kHz, 10% THD)

AUDIO IN (stereo mini jack):
Sensitivity 800 mV, impedance 22 kilohms

PHONES (stereo mini jack):
Accepts headphones with an impedance of 8 Ω or more
SPEAKER: impedance
HCD-EC78P: 8 Ω
HCD-EC68P: 6 Ω

System: Compact disc and digital audio system

Laser: Semiconductor laser (

λ

=770 – 810 nm)

Emission duration: continuous
Frequency response: 20 Hz – 20 kHz
Signal-to-noise ratio: More than 90 dB
Dynamic range: More than 88 dB

FM stereo, FM/AM superheterodyne tuner
Antenna:

FM lead antenna
AM loop antenna

FM tuner section:

Tuning range
North American model: 87.5 – 108.0 MHz (100 kHz step)
UK and Australian models: 87.5 – 108.0 MHz (50 kHz step)
Intermediate frequency: 10.7 MHz

AM tuner section:

Tuning range
North American model:
530 – 1,710 kHz (with 10 kHz tuning interval)
531 – 1,710 kHz (with 9 kHz tuning interval)
Australian model:

UK model:

531 – 1,710 kHz (with 9 kHz tuning interval)
530 – 1,710 kHz (with 10 kHz tuning interval)
Intermediate frequency: 450 kHz

North American model: AC 120 V, 60 Hz

UK model: AC 230 V, 50/60 Hz

UK model: 160 W

Australian model: AC 230 – 240 V, 50/60 Hz

USA model: 210 W
Canadian model: 270 VA

110 W

Approx. 200 × 306 × 415 mm

Approx. 5.8 kg

Approx. 4.7 kg

Power output (rated):

Low channel
50 W + 50 W (at 8 Ω, 1 kHz, 1% THD)
High channel
50 W + 50 W (at 8 Ω, 8 kHz, 1% THD)

RMS output power (reference):

Low channel
70 W + 70 W (per channel at 8 Ω, 1 kHz, 10% THD)
High channel
70 W + 70 W (per channel at 8 Ω, 8 kHz, 10% THD)

531 – 1,602 kHz (with 9 kHz tuning interval)
Intermediate frequency: 450 kHz

0.5 W (in Power Saving Mode)

Approx. 6.1 kg

(HCD-EC78P The United States model only)

(HCD-EC68P The United States model only)

Notes on chip component replacement
• 

Never reuse a disconnected chip component.

• 

Notice that the minus side of a tantalum capacitor may be dam-
aged by heat.

Flexible Circuit Board Repairing
• 

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.

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

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

COMPONENTS  IDENTIFIED  BY  MARK 0 OR  DOTTED  LINE  
WITH  MARK 0 ON  THE  SCHEMATIC  DIAGRAMS  AND  IN  
THE  PARTS  LIST  ARE  CRITICAL  TO  SAFE  OPERATION.
REPLACE  THESE  COMPONENTS  WITH  SONY  PARTS 

LES  COMPOSANTS  IDENTIFIÉS  PAR  UNE  MARQUE  0 SUR  
LES  DIAGRAMMES  SCHÉMATIQUES  ET  LA  LISTE  DES  
PIÈCES  SONT  CRITIQUES  POUR  LA  SÉCURITÉ  DE  FONC-
TIONNEMENT.  NE  REMPLACER  CES  COM-  POSANTS  QUE  
PAR  DES  PIÈCES  SONY  DONT  LES  NUMÉROS  SONT  DON-
NÉS  DANS  CE  MANUEL  OU  DANS  LES  SUPPLÉMENTS  
PUBLIÉS  PAR  SONY.

SAFETY  CHECK-OUT
After correcting the original service problem, perform the follow-
ing safety check before releasing the set to the customer:
Check the antenna terminals, metal trim, “metallized” knobs, 
screws, and all other exposed metal parts for AC leakage.
Check leakage as described below.

LEAKAGE  TEST
The AC leakage from any exposed metal part to earth ground and 
from all exposed metal parts to any exposed metal part having a 
return to chassis, must not exceed 0.5 mA (500 microamperes.). 
Leakage current can be measured by any one of three methods.
1.  A commercial leakage tester, such as the Simpson 229 or RCA 

WT-540A. Follow the manufacturers’ instructions to use these 
instruments.

2.  A battery-operated AC milliammeter. The Data Precision 245 

digital multimeter is suitable for this job.

3.  Measuring the voltage drop across a resistor by means of a 

VOM or battery-operated AC voltmeter. The “limit” indication 
is 0.75 V, so analog meters must have an accurate low-voltage 
scale. The Simpson 250 and Sanwa SH-63Trd are examples 
of a passive VOM that is suitable. Nearly all battery operated 
digital multimeters that have a 2 V AC range are suitable.  (See 
Fig. A)

  .............................................   3

  ..................................................................   6

3-1. Disassembly 

Flow 

...........................................................  10

3-2.  Side Panel (L)/(R) ...........................................................   11
3-3. Panel 

(Top) 

......................................................................  11

3-4. MAIN 

Board 

...................................................................  12

3-5.  Front Panel Block (EC78P: UK) ....................................   12
3-6.  Front Panel Block (EC68P/EC78P: US, Canadian) ........   13
3-7.  Back Panel Block ............................................................   13
3-8.  3 CD Mechanism Block (EC78P: UK) ...........................   14
3-9.  Base Unit (EC78P: UK) ..................................................   14
3-10.  1 CD Mechanism Block 
 

(EC68P/EC78P: US, Canadian) ......................................   15

3-11.  Base Unit (EC68P/EC78P: US, Canadian) .....................   15
3-12.  Belt (EC68P/EC78P: US, Canadian) ..............................   16
3-13.  Belt (EC78P: UK) ...........................................................   16
3-14.  OP Base Assy (KSM-213D) ...........................................   17

TEST  MODE 

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

ADJUSTMENTS 

 ........................   22

6-1.  Block Diagram - CD SERVO, TUNER Section - ...........   25
6-2.  Block Diagram - MAIN Section - ...................................   26
6-3.  Printed Wiring Board - CD Board - ................................   28
6-4.  Schematic Diagram - CD Board - ...................................   29
6-5.  Printed Wiring Boards - MAIN Section - .......................   30
6-6.  Schematic Diagram - MAIN Section (1/3) - ...................   31
6-7.  Schematic Diagram - MAIN Section (2/3) - ...................   32
6-8.  Schematic Diagram - MAIN Section (3/3) - ...................   33
6-9.  Printed Wiring Board - HI AMP Board (EC78P) - .........   34
6-10.  Schematic Diagram - HI AMP Board (EC78P) - ............   34
6-11.  Printed Wiring Board - LOW AMP Board - ...................   35
6-12.  Schematic Diagram - LOW AMP Board - ......................   35
6-13.  Printed Wiring Board - PANEL Board - .........................   36
6-14.  Schematic Diagram - PANEL Board - ............................   37
6-15.  Printed Wiring Boards - KEY Section - ..........................   38
6-16.  Schematic Diagram - KEY Section - ..............................   38
6-17.  Printed Wiring Board - MOTOR Board 
 

(EC68P/EC78P: US, Canadian models) - .......................   39

6-18.  Schematic Diagram - MOTOR Board 
 

(EC68P/EC78P: US, Canadian models) - .......................   39

6-19.  Printed Wiring Board - PT Board - .................................   40
6-20.  Schematic Diagram - PT Board - ....................................   41

7-1. Panel 

Section 

...................................................................  47

7-2.  Front Panel Section .........................................................   48
7-3. Chassis 

Section 

...............................................................  49

7-4. Main 

Section 

...................................................................  50

7-5.  3 CD Mechanism Section (EC78P: UK) 
 (CDM88A-K6BD90-WOD) 

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

51

7-6.  1 CD Mechanism Section (Except EC78P: UK) 
 (CDM77B-K6BD90-WOD) 

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

52

  ..............................   53

The laser diode in the optical pick-up block may suffer electrostat-
ic 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 fl exible board is easily damaged and should be handled with 
care.

NOTES  ON  LASER  DIODE  EMISSION  CHECK
The laser beam on this model is concentrated so as to be focused 
on the disc refl ective surface by the objective lens in the optical 
pickup block. Therefore, when checking the laser diode emission, 
observe from more than 30 cm away from the objective lens.

UNLEADED  SOLDER
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 viscou-s (sticky, less prone to fl ow) 
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.

RELEASING  THE  DISC  TRAY  LOCK
The disc tray lock function for the antitheft of an demonstration 
disc in the store is equipped.

Releasing Procedure:
1. Press 

[I/

1

] button to turn the power on.

2.  Press the [FUNCTION] button to select CD function.
3.  While pressing the [

x

] button, press the [

Z

] button for more 5 

seconds).

4.  The message “UNLOCKED” is displayed and the disc tray is 

unlocked.

Note: When 

“

LOCKED

”

 is displayed, the slot lock is not released by 

turning power on/off with the

 [I/1]

 button.