WQ-790W
SERVICE MANUAL
No. S7852WQ790W//
WQ-790W
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• In the interests of user-safety the set should be restored to its original |
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condition and only parts identical to those specified should be used. |
CONTENTS |
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SPECIFICATIONS ............................................................................................................................................................... |
1 |
VOLTAGE SELECTION ....................................................................................................................................................... |
2 |
AC POWER SUPPLY CORD AND PLUG ........................................................................................................................... |
2 |
FITTING OF DIAL POINTER ............................................................................................................................................... |
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NAMES OF PARTS ............................................................................................................................................................. |
3 |
DISASSEMBLY .................................................................................................................................................................... |
4 |
ADJUSTMENT ..................................................................................................................................................................... |
5 |
NOTES ON SCHEMATIC DIAGRAM .................................................................................................................................. |
6 |
VOLTAGE ............................................................................................................................................................................ |
7 |
TYPES OF TRANSISTOR AND LED................................................................................................................................... |
7 |
SCHEMATIC DIAGRAM / WIRING SIDE OF P.W.BOARD ................................................................................................. |
8 |
PARTS GUIDE / EXPLODED VIEW |
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SPECIFICATIONS
● General
Power source: |
AC 110-127 V/220-240 V, |
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50/60 Hz |
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DC 15 V ["D" size (UM/SUM- |
Power consumption: |
1, R20 or HP-2) battery × 10] |
20 W |
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Output power: |
PMPO; 120 W (60 W + 60 W) |
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(AC operation) |
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MPO (Max.); 30 W |
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(15 W + 15 W) (AC operation) |
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RMS; 15 W (7.5 W + 7.5 W) |
Speakers: |
(DC operation, 10 % T.H.D.) |
12 cm (4-3/4") free-edge |
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speaker × 2 |
Input terminal: |
5 cm (2") surround speaker × 2 |
MIC 1/2; 1 mV/600 ohms |
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Output terminal: |
CD/LINE; 350 mV/47 kohms |
Headphones; 16-50 ohms |
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Dimensions: |
(recommended; 32 ohms) |
Width; 630 mm (24-13/16") |
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Height; 205 mm (8-1/8") |
Weight: |
Depth; 215 mm (8-1/2") |
5.3 kg (11.7 lbs.) without bat- |
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teries |
● Radio section
Frequency range: |
FM; 88 - 108 MHz |
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SW1; 2.3 |
- 7.3 MHz |
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SW2; 7.3 |
- 22 MHz |
MW; 526.5 - 1,606.5 kHz
● Tape recorder section
Frequency response: |
60 |
- 12,000 Hz (Normal tape) |
Signal/noise ratio: |
40 |
dB (TAPE 1, recording/playback) |
Wow and flutter: |
55 |
dB (TAPE 2, playback) |
0.15 % (WRMS) |
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Motor: |
DC 15 V electric governor |
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Bias system: |
AC bias |
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Erase system: |
Magnet erase |
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Specifications for this model are subject to change without prior notice.
This document has been published to be used SHARP CORPORATION for after sales service only.
The contents are subject to change without notice.
WQ-790W
FOR A COMPLETE DESCRIPTION OF THE OPERATION OF THIS UNIT, PLEASE REFER
TO THE OPERATION MANUAL.
VOLTAGE SELECTION
Before operating the unit on mains, check the preset voltage. If the voltage is different from your local voltage, adjust the voltage as follows: Slide the AC power supply socket to the visible indication of the side of your local voltage.
AC POWER SUPPLY CORD AND PLUG
9FF24801830210 |
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9FF26802125120 |
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9FF24801600292 |
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9FF26802125210 |
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FITTING OF DIAL POINTER
1.Remove the main PWB. Attach the dial pointer as shown arrow A on the front cabinet, putting it into the section indicated by arrow B .
2.Install the main PWB in the front cabinet and secure it with the four screws.
3.Turn the tuning control knob in the direction indicated by C . Set the dial pointer to point "0", and then make the rest of
the adjustments. |
Dial Pointer |
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(234) |
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Front Cabinet |
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Dial Pointer (234) |
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"0" Point |
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A |
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Tuning Control |
C |
Knod (233) |
B
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Screw (608) |
Dial Drum (231) |
ø3x10mm |
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Main PWB |
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Figure 2 |
– 2 –
WQ-790W
NAMES OF PARTS
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1 |
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13 |
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14 |
15 |
2 3 |
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7 |
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9 10 11 12 |
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16 17 18 19 20 21 22 23 |
24 |
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29 |
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33 34 |
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36 |
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30 |
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25 |
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31 |
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26 |
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32 |
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27 |
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28 |
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1. |
(TAPE 1) |
Cassette Compartment |
13. |
(TAPE 2) Cassette Compartment |
27. |
Power/(TAPE 2) Play Direction |
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2. |
(TAPE 1) |
Record Button: |
14. |
Full-Range Speaker |
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28. |
Indicators |
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3. |
(TAPE 1) |
Play Button: |
15. |
Surround Speaker |
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Built-in Microphone |
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4. |
(TAPE 1) |
Rewind Button: |
16. |
Mixing Microphone Sockets |
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29. |
Dubbing Speed/Built-in |
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5. |
(TAPE 1) |
Fast Forward Button: |
17. |
Mixing Microphone Volume |
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30. |
Microphone/FM Mode Switch |
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Control |
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Extra Bass Control: X-BASS |
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6. |
(TAPE 1) |
Stop/Eject Button: |
18. |
Surround On/Off Switch |
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31. |
Graphic Equalizer Controls |
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7. |
(TAPE 1) |
Pause Button: |
19. |
Surround Mode Select Switch |
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32. |
Volume Control |
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8. |
(TAPE 2) |
Reverse Mode Switch: |
20. |
Function Selector Switch |
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33. |
FM/SW Telescopic Rod Aerial |
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9. |
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21. |
Surround Mode Indicators |
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34. |
CD/Line Input Sockets |
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(TAPE 2) |
Play Button: |
22. |
Band Selector Switch |
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35. |
Headphone Socket |
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10. |
(TAPE 2) |
Fast Wind Buttons: |
23. |
Tuning Control |
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36. |
Beat Cancel Switch |
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11. |
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24. |
Fine Tuning Control |
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37. |
Battery Compartment |
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(TAPE 2) |
Stop/Eject Button: |
25. |
Spectrum Analyzer |
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38. |
AC Power Input Socket |
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12. |
(TAPE 2) |
Direction Switch: |
26. |
FM Stereo Indicator |
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39. |
AC Voltage Selector |
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– 3 –
WQ-790W
DISASSEMBLY
Caution on Disassembly
Follow the below-mentioned notes when disassembling the unit and reassembling it, to keep it safe and ensure excellent performance:
1.Take cassette tape out of the unit.
2.Be sure to remove the power supply plug from the wall outlet before starting to disassemble the unit and remove the batteries from the unit.
3.Take off nylon bands or wire holders where they need to be removed when disassembling the unit. After servicing the unit, be sure to rearrange the leads where they were before disassembling.
4.Take sufficient care on static electricity of integrated circuits and other circuits when servicing.
STEP |
REMOVAL |
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PROCEDURE |
FIGURE |
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1 |
Front Cabinet/ |
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1. Battery Compartment Lid. |
4-1 |
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Rear Cabinet |
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(A1)x1 |
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2. |
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...................Screw |
(A2)x1 |
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3. |
Screw ................... |
(A3)x8 |
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4. |
Socket .................. |
(A4)x1 |
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2 |
Tape mechanism |
1. Screw ................... |
(B1)x2 |
4-2 |
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2. |
Socket .................. |
(B2)x4 |
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3. Open the cassette holder. |
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4. |
Screw ................... |
(B3)x6 |
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3 |
Main PWB |
1. Knob ..................... |
(C1)x1 |
4-2 |
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2. |
Screw ................... |
(C2)x4 |
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3. |
Socket .................. |
(C3)x5 |
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4 |
Graphic Equalizer |
1. Screw ................... |
(D1)x5 |
4-3 |
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PWB |
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5 |
Volume PWB |
1. Knob ..................... |
(E1)x1 |
4-3 |
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2. |
Screw ................... |
(E2)x2 |
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3. |
Screw ................... |
(E3)x1 |
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6 |
Power PWB |
1. Screw ................... |
(F1)x1 |
4-4 |
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2. |
Bracket ................. |
(F2)x1 |
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(A4)x1
Main PWB Front
Cabinet
(A2)x1 ø2.6x10mm
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Rear |
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(A1)x1 |
Cabinet |
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(A3)x8 |
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ø3x20mm |
Figure 4-1
Open
Casette Holder (Left/Right)
Open
(B1)x1
ø3x20mm
Front Cabinet |
(B3)x6 |
(B1)x1 |
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ø3x10mm |
ø3x20mm |
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Tape Mechanism |
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(C1)x1 |
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(C3)x4 |
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(B2)x1 |
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(C3)x1 |
(B2)x3 |
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(C2)x4 |
Main PWB |
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ø3x10mm |
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Figure 4-2
Graphic
Equalizer PWB
Front Cabinet
Volume PWB
(E1)x1
(D1)x5 ø3x10mm
(E2)x2 |
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ø3x10mm |
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(E3)x1 |
Lug Wire |
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ø2x6mm |
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Figure 4-3 |
Rear Cabinet
(F2)x1
Power
PWB
Pull
(F1)x1
ø3x10mm
Power
Transformer
Figure 4-4
– 4 –
WQ-790W
ADJUSTMENT
MECHANISM SECTION
• Driving Force Check
Torque Meter |
Specified Value |
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Play: TW-2412 |
Tape 1: Over 60 g |
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Tape 2: Over 50 g |
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• Torque Check
Torque Meter |
Specified Value |
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Tape 1 |
Tape 2 |
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Play: TW-2111 |
30 to 60 g.cm |
30 to 60 g.cm |
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Fast forward: TW-2231 |
80 to 135 g.cm |
55 to 120 g.cm |
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Rewind: TW-2231 |
80 to 135 g.cm |
55 to 120 g.cm |
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• Head Azimuth
Test Tape |
Instrument Connection |
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MTT-114 |
Headphones Socket |
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(Load resistance: 32 ohms) |
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*Open the cassette holder, and load the test tape directly into the mechanism. (Do not load the tape into the cassette holder.)
• Tape Speed (Normal only)
Test Tape |
Adjustment |
Specified |
Instrument |
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Point |
Value |
Connection |
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MTT-111 |
Tape 1,2:VR501 |
3,000 ± 60 Hz |
Headphones |
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Socket |
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(Loadresistance: |
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32 ohms) |
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DECK SECTION
•Bias Oscillation
•Beat Cancel Switch: A
Adjustment Point |
Specified value |
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Instrument |
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Connection |
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T301 |
100 kHz + 4 kHz |
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Pin 1 of CNS108 |
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Specified Value |
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Beat Cancel |
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A: 100 |
± 4 kHz |
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B: 94 |
± 4 kHz |
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C: 104 ± 4 kHz |
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TUNER SECTION
fL: Low-range frequency fH: High-renge frequency
• FM IF/RF
Test Stage |
Specified Value/ |
Instrument |
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Adjusting |
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Connection |
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Point |
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IF |
T201 |
Input: FM Antenna |
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Detection |
T202 |
Output:Pin 9 of IC202 |
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Band |
fL: L202 |
Input: Antenna |
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Coverage |
fH: TC202 |
Output: Headphone Socket |
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Tracking |
fL(88.0 MHz): L201 |
(Load resistance: |
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fH(108 MHz): TC201 |
32 ohms) |
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• AM IF/RF
Test Stage |
Specified Value/ |
Instrument |
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Adjusting |
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Connection |
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Point |
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IF |
T203 |
Input: Antenna |
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Output: Pin 9 of IC202 |
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MW Band |
fL: L203 |
Input: Antenna |
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Coverage |
fH: TC203 |
Output: Headphone Socket |
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(Load resistance |
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MW Tracking |
fL(600 kHz): L206 |
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fH(1,400 kHz):TC207 |
32 ohms) |
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SW1 Band |
fL(2.3 MHz): L204 |
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Coverage |
fH(7.3 MHz): TC204 |
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SW1 |
fL(2.6 MHz): L207 |
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Tracking |
fH(6 MHz): TC209 |
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SW2 Band |
fL(7.3 MHz): L205 |
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Coverage |
fH(22 MHz): TC205 |
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SW2 |
fL(8.5 MHz): L208 |
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Tracking |
fH(19 MHz): TC210 |
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• VCO Frequency
Adjustment |
Specified value |
Instrument Connection |
Point |
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VR201 |
76 kHz ± 200 Hz |
Pin 13, Pin 21 and ground |
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of IC202 |
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Note:
After preparing the test circuit shown in Fig. 5, connect the Pin 13, Pin 21 and ground of the IC202 with the test circuit, and measure the value.
Pin 13 of IC202 |
Pin 21 of IC202 |
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D |
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G |
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FET: 2SK212 |
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10 pF |
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(or Other 2SK Type FET.) |
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S |
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1M ohm |
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0.1 F |
TO FREQUENCY |
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10K ohm |
COUNTER |
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Figure 5 VCO FREQUENCY TEST CIRCUIT
– 5 –
WQ-790W
CNS110
T301
BIAS
OSCILLATION
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FM IF |
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FM |
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fL |
T201 |
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TRACKING |
fH |
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CNS108 |
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T203 |
1 |
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1 |
AM IF |
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IC201 |
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L201 |
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2 |
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L202 |
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3 |
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9 |
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1 |
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4 |
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TC |
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IC202 |
TC |
TC204 |
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VCO |
201 |
202 |
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13 |
21 |
T202 TC |
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FM |
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VR201 |
207 |
TC |
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DETECTION |
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203 |
TC205 |
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TC210 |
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SW2 |
fH |
TC209 |
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TRACKING |
fL |
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L208 |
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fH |
FM BAND |
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fL |
COVERAGE |
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fH |
SW1 BAND |
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fL |
COVERAGE |
L203 |
fL |
MW BAND |
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COVERAGE |
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L204 |
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fL |
SW2 BAND |
L205 |
fH |
COVERAGE |
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fH |
MW BAND |
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COVERAGE |
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MW |
fH |
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TRACKING |
fL |
MAIN PWB |
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SW1 |
fH |
MW |
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SW1 |
TRACKING |
fL |
L206 |
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L207 |
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Figure 6 ADJUSTMENT POINTS
NOTES ON SCHEMATIC DIAGRAM
•Resistor:
To differentiate the units of resistors, The symbol as K and M are used: the symbol K means 1000 ohm and the symbol M means 1000 kohm and the resistor without any symbol is an ohm resistor. The resistor designated “Fusible” is a fuse type resistor.
•Capacitor:
To indicate the unit of capacitor, a symbol P is used: this symbol P means pico-farad and the unit of the capacitor without such a symbol is microfarad. As to electrolytic capacitor, the expression “capacitance/withstand voltage” is used.
(CH),(RH),(UJ): Temperature compensation (ML): Mylar type
(S): Styrol type
•The indicated voltage in each section is the one measured by Digital Multimeter between such a section and the chassis with no signal given.
•Schematic diagram and Wiring Side of P.W. Board for this model are subject to change for improvement without prior notice.
•Parts marked with “
” ( 
) are important for maintaining the safety of the set. Be sure to replace these parts with specified ones for maintaining the safety and performance of the set.
REF. NO. |
DESCRIPTION |
POSITION |
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SW201 |
BAND SELECTOR |
FM |
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SW301 |
BEAT CANCEL |
C |
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SW302 |
RECORD/PLAYBACK |
PLAYBACK |
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SW401 |
SURROUND MODE |
LIVE |
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SELECT |
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SW402 |
SURROUND ON/OFF |
OFF |
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SW403 |
DUBBING SPEED/ |
HIGH/FM STEREO |
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BUILT-IN MICROPHONE/ |
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FM MODE |
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SW404 |
FUNCTION SELECTOR |
TAPE |
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SW501 |
TAPE 2 MAIN |
OFF |
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SW502 |
TAPE 1 MAIN |
OFF |
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SW503 |
TAPE 2 PLAY |
OFF |
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SW504 |
TAPE 2 DIRECTION |
A |
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SW505 |
VOLTAGE SELECTOR |
AC220-240V |
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– 6 –
WQ-790W
CNS110
T301
BIAS
OSCILLATION
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FM IF |
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FM |
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fL |
T201 |
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TRACKING |
fH |
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CNS108 |
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T203 |
1 |
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1 |
AM IF |
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IC201 |
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L201 |
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2 |
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L202 |
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3 |
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9 |
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1 |
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4 |
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TC |
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IC202 |
TC |
TC204 |
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VCO |
201 |
202 |
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13 |
21 |
T202 TC |
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FM |
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VR201 |
207 |
TC |
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DETECTION |
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203 |
TC205 |
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TC210 |
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||||
SW2 |
fH |
TC209 |
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||
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|
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|||
TRACKING |
fL |
|
|
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|
L208 |
|
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|
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|
fH |
FM BAND |
|
fL |
COVERAGE |
|
fH |
SW1 BAND |
|
fL |
COVERAGE |
L203 |
fL |
MW BAND |
|
COVERAGE |
|
L204 |
|
|
|
fL |
SW2 BAND |
L205 |
fH |
COVERAGE |
|
fH |
MW BAND |
|
COVERAGE |
|
|
MW |
fH |
|
|
|
TRACKING |
fL |
MAIN PWB |
|
|
|
|
|
SW1 |
fH |
MW |
|
SW1 |
TRACKING |
fL |
L206 |
|
L207 |
|
|
|
Figure 6 ADJUSTMENT POINTS
NOTES ON SCHEMATIC DIAGRAM
•Resistor:
To differentiate the units of resistors, The symbol as K and M are used: the symbol K means 1000 ohm and the symbol M means 1000 kohm and the resistor without any symbol is an ohm resistor. The resistor designated “Fusible” is a fuse type resistor.
•Capacitor:
To indicate the unit of capacitor, a symbol P is used: this symbol P means pico-farad and the unit of the capacitor without such a symbol is microfarad. As to electrolytic capacitor, the expression “capacitance/withstand voltage” is used.
(CH),(RH),(UJ): Temperature compensation (ML): Mylar type
(S): Styrol type
•The indicated voltage in each section is the one measured by Digital Multimeter between such a section and the chassis with no signal given.
•Schematic diagram and Wiring Side of P.W. Board for this model are subject to change for improvement without prior notice.
•Parts marked with “
” ( 
) are important for maintaining the safety of the set. Be sure to replace these parts with specified ones for maintaining the safety and performance of the set.
REF. NO. |
DESCRIPTION |
POSITION |
|
|
|
SW201 |
BAND SELECTOR |
FM |
|
|
|
SW301 |
BEAT CANCEL |
C |
|
|
|
SW302 |
RECORD/PLAYBACK |
PLAYBACK |
|
|
|
SW401 |
SURROUND MODE |
LIVE |
|
SELECT |
|
|
|
|
SW402 |
SURROUND ON/OFF |
OFF |
|
|
|
SW403 |
DUBBING SPEED/ |
HIGH/FM STEREO |
|
BUILT-IN MICROPHONE/ |
|
|
FM MODE |
|
|
|
|
SW404 |
FUNCTION SELECTOR |
TAPE |
|
|
|
SW501 |
TAPE 2 MAIN |
OFF |
|
|
|
SW502 |
TAPE 1 MAIN |
OFF |
|
|
|
SW503 |
TAPE 2 PLAY |
OFF |
|
|
|
SW504 |
TAPE 2 DIRECTION |
A |
|
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|
SW505 |
VOLTAGE SELECTOR |
AC220-240V |
|
|
|
– 6 –
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