STR-DB840, STR-DB940 - Sony Audio Service Manual (repair manual)

US Model

Canadian Model

AEP Model

UK Model

STR-DB840/DB940

E Model

Australian Model

Chinese Model

STR-DB940

Photo: STR-DB940 (AEP and UK models) (Black type)

– Continued on next page –

Manufactured under license from Dolby laboratories. “Dolby”, “AC-
3”, “Pro Logic” and the double-D symbol 

;

 are trademarks of Dolby

Laboratories.
Manufactured under license from Digital Theater Systems, Inc. US
Pat. No. 5,451,942 and other worldwide patents issued and pending.
“DTS” an d “DTS Digital Surround” are trademarks of Digital Theater
Systems, Inc.

2

• Abbreviation

AU : Australian model
CA : Canadian model
CED : AEP and UK models

CN : Chinese model
SP

: E model

U

: US model

3

– Rear View –

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

aged by heat.

• Keep the temperature of the 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.

Ω

µ

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.

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 pas-
sive VOM that is suitable. Nearly all battery operated digital
multimeters that have a 2 V AC range are suitable.  (See Fig. A)

Model

DB940: US model

DB940: Canadian model

E model

Chinese model

Australian model

DB940: AEP and UK models

DB840: US model

DB840: AEP and UK models

DB840: Canadian model

Part No.

4-227-151-0s

4-227-151-1s

4-227-151-2s

4-227-151-3s

4-227-151-4s

4-227-151-5s

4-227-151-7s

4-227-151-8s

4-227-151-9s

0

0

0

4

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

5

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

7

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

4-1. Block Diagram – MAIN Section (1/2) – ........................ 11
4-2. Block Diagram – MAIN Section (2/2) – ........................ 12
4-3. Block Diagram

– DISPLAY/POWER SUPPLY Section – ...................... 13

4-4. Note for Printed Wiring Boards and

 Schematic Diagrams ...................................................... 14

4-5. Schematic Diagram – DIGITAL Board (1/3) – .............. 15
4-6. Schematic Diagram – DIGITAL Board (2/3) – .............. 16
4-7. Schematic Diagram – DIGITAL Board (3/3) – .............. 17
4-8. Printed Wiring Board

– DIGITAL Board (Component Side) – ......................... 18

4-9. Printed Wiring Board

– DIGITAL Board (Conductor Side) – ........................... 19

4-10. Printed Wiring Boards

– VIDEO/JOINT (1) (Q) Boards (DB840) – .................. 20

4-11. Schematic Diagram

– VIDEO/JOINT (1) (Q) Boards (DB840) – .................. 21

4-12. Printed Wiring Boards

– OSD/JOINT (2) (Q) Boards (DB940) – ...................... 22

4-13. Schematic Diagram

– OSD/JOINT (2) (Q) Boards (DB940) – ...................... 23

4-14. Printed Wiring Board – AU SW Board – ....................... 24
4-15. Schematic Diagram – AU SW Board – .......................... 25
4-16. Printed Wiring Board – S-VIDEO Board – .................... 26
4-17. Schematic Diagram – S-VIDEO Board – ....................... 27
4-18. Printed Wiring Board –DISPLAY Board – .................... 28
4-19. Schematic Diagram – DISPLAY Board – ...................... 29
4-20. Printed Wiring Board – MAIN Board – ......................... 30
4-21. Schematic Diagram – MAIN Board (1/3) – ................... 31
4-22. Schematic Diagram – MAIN Board (2/3) – ................... 32
4-23. Schematic Diagram – MAIN Board (3/3) – ................... 33
4-24. Printed Wiring Boards – H.P/MUTING/POWER/SW/

VOL/VIDEO 3 Boards – ................................................. 34

4-25. Schematic Diagram – H.P/MUTING/POWER/SW/

VOL/VIDEO 3 Boards – ................................................. 35

4-26. Printed Wiring Boards – 5.1 IN/BIAS (C)/BIAS (L)/

BIAS (LS)/BIAS (R)/BIAS (RS) Boards – .................... 36

4-27. Schematic Diagram – 5.1 IN/BIAS (C)/BIAS (L)/

BIAS (LS)/BIAS (R)/BIAS (RS) Boards – .................... 37

4-28. Printed Wiring Boards –DC (1)/DC (2) Boards – .......... 38
4-29. Schematic Diagram –DC (1)/DC (2) Boards – .............. 39
4-30. Printed Wiring Boards –AC/SP Boards – ....................... 40
4-31. Schematic Diagram – AC/SP Boards – .......................... 41
4-32. IC Pin Function Description ........................................... 48

................................................ 59

............................... 63