Technics SAEX 900 Service Manual

Page 2

SA-Ex900
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 professional technicians. Any attempt to service or repair the product or products dealt with in this sen/ice
information by anyone else could result in serious injury or death.

I General Notes =
. 1. Specifications are subject to change without notice.
Power consumption 265W, 335VA (In standoy condition : 2W) Weight and dimensions are approximate.
power supply AC 120V, 60Hz 2. Total harmonic distortion Is measured by the digital spectrum
Dimensions (W x H x D) 430 x 158 x 358 mm analyzer.
(1615/,5" x 67/32" x 143/32")
Weight 10.3 kg (22.7 lb.)
I Contents
PAGE PAGE
0 SAFETY PRECAUTION .............................................................. 2 ' TERMINAL GUIDE OF ICs, TRANSISTORS & DIODES.. 17 ~ 18
- BEFORE REPAIR AND ADJUSTMENT ...................................... 2 ° SCHEMATIC DIAGRAM ...... . 18~ 35
- PROTECTION CIFlCUITRY ......................................................... 2 - PRINTED CIRCUIT BOARD 36 ~ 43
' OPERATION CHECKS AND MAIN COMPONENT REPLACEMENT 3 ~ 7 ' CABINErPAFlTS LOCATION 44
- FAN MOTOR TROUBLESHOOTING .......................................... 8 ~ REPLACEMENT PARTS LIST .......................................... 45 ~ 47
0 TROUBLESHOOTING 9 ~ 12 ' RESISTORS&CAPACITORS 48 ~ 52

' BLOCK DIAGRAM.
- TERMINAL FUNCTIONS OF IC

13 ~ 16 - PACKAGING .......................

I Safety Precaution (This "Safety Precaution" is applied only in U.S.A.)

Before servicing, unplug the power cord to prevent an electric shock . Antenna
When replacing parts ,use only manufacturers recommended components for safety . e'mma
Check the condition of the power cord .Fleplace if wear or damage is evident .

After servicing ,be sure to restore the lead dress, insulation barriers ,insulation papers ,shields ,etc . EXPmd/
Before returning the serviced equipment to the customer, be sure to make the following insulation 383? '
resistance test to prevent the customer from being exposed to a shock hazard .

Vii-93P."

Ohmmeter
Fig. 1
Resistance = SMQ - 5.2MQ

. INSULATION RESISTANCE TEST

1. Unplug the power cord and short the two prongs of the plug with a Jumper wire .

2. Turn on the power switch .

3. Measure the resistance value with ohmmeter between the jumper AC plug and each exposed metal
cabinet part ,such as screwheads, antenna ,control shafts ,handie brackets , etc. Equipment with antenna
terminals should read between 8M!) and 5.2M!) to all exposed parts* .(Fig. 1 ) Equipment without
antenna terminals should read approximately infinity to all exposed parts . (Fig. 2 ) Exposed , a
*Note :Some exposed parts may be isolated from the chassis by design. These will read infinity . 'e'a' "

4. If the measurement is outside the specified limits .there is a possibility of a shock hazard .The equipment
should be repaired and rechecked before it is returned to the customer. fig 2 '

Resistance = Approx

I Before Repair and Adjustment

Disconnect AC power, discharge 4 Power Supply Capacitors C703, C704, C705 and C706 through a 109 , 5W resistor to ground.
DO NOT SHORT-CIRCUIT DIFIECTLY (with a screwdriver blade, for instance), as this may destroy solid state devices.
After repairs are completed, restore power gradually using a variac, to avoid overcurrent.

Current consumption at AC 120 V, 60Hz in NO SIGNAL mode should be 500 ~ 1000 mA.

I Protection Circuitry

The protection circuitry may have operated if either of the follow- If this occurs, follow the procedure outlines below:
ing conditions are noticed: 1. Turn off the power.
- No sound is heard when the power is turned on. 2. Determine the cause of the problem and correct it.
- Sound stops during a performance. 3. Turn on the power once again after one minute.
The function of this circuitry is to prevent circuitry damage if, for
example, the positive and negative speaker connection wires Note:
are "shorted", or if speaker systems with an impedance less than When the protection circuitry functions, the unit will not operate
the indicated rated impedance of the amplifier are used. unless the power is first turned off and then on again.