Technics SAEH 780 GN Service Manual

Page 1

AD02061 1 3C3

Service Manual

Tuner/Amplifier
83-7595
SA-E H 780G N
1 W Colour
(N) ................... Gold Type
System SC-EH780
Sound Processor SH-EH780
Because of unique lnterconnecting cables, when a component Tuner/Amp'ifie' SA'EHno
requires service, send or bring in the entire system. CD Changer SL-EH730
Cassette Deck FtS-DV280
Front Speakers" SB-DV280
Center Speaker* SB-P095
Specifications Surround Speakers* SBAP895
_ _ _ _ *2 Made in Singapore.
Amplifier section FM tuner section
Power output (LIR both channel driven): Frequency range: 87.50 - 108.00 MHz (0.05 MHz steps)
Stereo mode; Sensitivity: 1.8 uv (IHF usable)
DIN 1 kHz, THD 1 % (High); 2 x 25 w (6 :2) SIM 26 GB: 1.5 uv
100 Hz, THD 1 % (Low); 2 x 45 W (8 £2) SIN (MONO): 70 dB (75 dB, IHF)
RMS 1 kHz, THD 10 % (High); 2 x 35 W (6 Q) Antenna terminal(s): 75 Q (unbalanced)
100 Hz, THD 10 % (Low); 2 x 65 W (8 9) AM tuner section
0 LOG'C "W59? _ Frequency range: 522 - 1629 kHz (9 kHz steps)
DIN FRONT 1 kHz, THD 1 % (High); 2 X 25 W (6 Q) 520 - 1630 kHz (10 kHZ steps)

100 Hz. THD 1 % (LOW); 2 x 45 W (8 9) Sensitivity (er 20 dB):
SURROUND 1 kHz. THD 1 %; 2 x 30 W (8 9) Timer section

CENTER 1 kHz, THD 1 as; so w (a n)
nus FRONT 1 kHz, THD 10 as, (High); 2 X 35 w (6 El)
100 Hz, THD 10%(Low); 2x65W (a :2)

Clock:
Fu notion:

500 uV/m

Quartz - lock type
Play timer (1 time, daily), Flec timer (1 time. daily),
Sleep (120 min, 30 min intervals)

o .
ign$ggND : tn: mg 12:; 2 X 3?) a i: 3; Setting intervals (Play/Rec): 1 minute - 23 hours'59- minutes
PMPO 1 kHz; 3,000 w (1 "n 'mewa's)
(High 6 9, Low, CENT., SUFlFt. a 12) General
Total harmonic distortion: 90W $UPP'Y1 AC 230 - 240 V, 50 H2
Rated power at 1 kHz; 1 % (6 9) Power consumption: 190 W
Halt power at 1 kHz; 0.1 % (6 52) Standby: 0-5 W
Load Impedance: Dimensions (WxHxD): 293x118.5x345 mm
FRONT (High); 6 o M855: 52 k9
(LOW); 8 9 Notes: Specifications are subject to change without notice.
SURROUND; 8 9 Mass and dimensions are approximate.
CENTER; 3 Q Total harmonic distortion is masured by the digital spectrum
DIGITAL s.woor=en: analyze,_
Center frequency; 60 Hz
LEVEL (VOL-20 dB); MID +3 dB, MAX +6 dB
A WAR N I NG

This service information is designed for experienced repair technicians only and is not designed for use by the general public.

It does not contain warnings or cautions to advise non-technical individuals of potential dangers in attempting to service a product.
Products powered by electricity should be serviced or repaired only by experienced protessional technicians. Any attempt to service
or repair the product or products dealt with in this service information by anyone else could result in serious injury or death.

Technics

© 2002 Matsushita Electric Industrial Co., Ltd, All

rights reserved. Unauthorized

distribution is a violation of law.

copying and

Page 2

SA-EH7BOGN

CONTENTS

Page
1 Before Repairs ------------------------------------------------------------------------ 2
2 Protection Circuitry ---------- "2

3 Ac "3
4 Location of Controls --------------------------------------------------------------- 4

lies --

5 Operation Checks and Component Replacement Prooeduress
5.1. Checking for the AC IN P.C.B
5.2. Checking for the operation P.C.B.
5.3. Checking for the main P.C.B. ----------------------------------------- 6
5.4. Replacement for the regulator transistor

5.5. Replacement for the power IC ------------

6 To Supply Power Source ........................................................ 3
7 Self-Diagnostic Function -------------------------------------------------------- 9
7.1. To display the malfunction code ..................................... g

1 Before Repairs

1.Turn off the power supply. Using a 10 Q, 10 W resistor,
connect both ends of power supply capacitors (C701, C703
and C702, 0704) in order to discharge the voltage.

2. Before turning the power supply on, after completion of
repair, slowly apply the primary voltage by using a power
supply voltage controller to make sure that the consumed
current at 50 Hz in NO SIGNAL mode should be shown
below with respectto supply voltage 240 V.

AC 240 V
100 - 350 mA

Power supply voltage
Consumed current 50 Hz

Page

7.2. To retum to the normal display --------------------------------------- 9

7.3. Display contents

8 Schematic Diagram Notes
9 Schematic Diagram --------------------------------------------------------------- 11
10 Printed Circuit Board Diagram ---------------------------
11 Type Illustration of le, Transistors and Diodes
12 Wiring Connection Diagram -------------------------------
13 Block Diagram ---------------------------------------------------------------------- 21
14 Terminal Function of me -----------------------------------------
14.1. ICQOt (CZBBFD000317):System Control/FL Drive

15 Replacement Parts List --------------------------------------------------------- 26
16 Cabinet Parts Location --------------------------------------------------------- 30
17 Packaging ----------------------------------------------------------------------------- 31

2 Protection Circuitry

The protection circuitry may have operated if either of the
following conditions is noticed:

o No sound is heard when the power is switched ON.
a Sound stops during a performance.

The functions of this circuitry is to prevent circuitry damage if,
for example, the positive and negative speaker connection
wires are shorted, or if speaker systems with an impedance
less than the indicated rated impedance of this unit are used.

If this occurs, follow the procedures outlined below.
1.Switch OFF the power.
2. Determine the cause of the problem and correct it.
3. Switch ON the power once again.

Note:

When the protection circuitry functions, the unit will not
operate unless the power is first switched OFF and then ON
again.