Panasonic sa eh 770 service manual

Page 2

SA-EH770

A WARNING

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.

CONTENTS

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

3 Accessories --

4 Caution for AC Mains Lea 4
5 Location of Controls --------------------------------------------------------------- 5
6 Operation Checks and Component Replacement Proceduress
6.1. Checking for the AC IN P.C.B. --------------------------------------- e
6.2. Checking for the operation P.C.B. ----------------------------------- e
6.3. Checking for the main P.C.B. ----------------------------------------- 7

6.4. Replacement for the regulator transistor- -- 8
6.5. Replacement for the power IC ------------ --8
7 To Supply Power Source -------------------------------------------------------- 9
8 Self-Diagnostic Function ------------------
8.1. To display the malfunction code --

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, C704) 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 respect to supply voltage 230/240 V.

AC 230 v | AC 240 v

100 ~ 350 mA

Power supply voltage
Consumed current 50 Hz

Page

8.2. To retum to the normal display ------------------------------------- 10

8.3. Display contents 1o

9 Schematic Diagram Notes 11
10 Schematic Diagram ------- 12
11 Printed Circuit Board Diagram ---------------------------------------------- 21
12 Type Illustration of le, Transistors and Diodes "-24
13 Wiring Connection Diagram ------------------------------- ...25
14 Block Diagram ---------------------------------------------------------------------- 26

15 Terminal Function of ICS ------------------------------------------------------ 31

15.1. IC901 (CZBBFDOOO297 System Control/FL Drive
16 Replacement Parts List --------------------------------------------
17 Cablnet Parts Location --------------------------------------------------------- 36
18 Packaging ----------------------------------------------------------------------------- 37

2 Protection Circuitry

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

. No sound is heard when the power is switched ON.

- Sound stops during a performance.
The functions 0t this circuitry is to prevent circuitry damage if.
for example, the positive and negative speaker connection
wires are shorted, or it 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.