Technics SEA 900 Service Manual

Page 1

U

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ORDER NO. AD9506164-CB

ervice Manual

Power Amplifier Amplifier
su-caoou
Remote Control Colour
Transmitter
. (K) : Black
Areas
Suffix for Area Colour
Model No.
(E) Europe
SE-Asoos (EB) Britain
(EG) Germany and italy (K)
(GC) Asia. Latin America,
Because of unique lnterconnecting cables, when a component . M'ddle Eas and Am
requires service, send or bring in the entire system. (GN) Oceania
_ _ . System: SU-A900D
Specifications (DIN 45 500) Com amplifier sumac"
20 Hz - 20 kHz continuous power output ' . ,
both channels driven 2x70 w (s o) PDWG ampme SE'AQOOS
1 kHz continuous power output
both channels driven (THD: 1%) 2x 85 W (8 Q)
2 X 120 W (4 £2)
63 Hz - 12.5 kHz continuous power output
both channels driven (T HD: 0.7%) 2 x 80 W (8 Q) 1
2x 105 w (4 $2) a
Total harmonic distortion 1
rated power at 20 Hz - 20 kHz 0.01% (8 Q) I GENERAL 1
Intermodulation distortion Power consumption : 285 W
(50 Hz: 7 kHz = 4:1, SMPTE) 0.007% (a 52) Power supply 5

Residual hum and noise 0.3 mV
Damping {actor 70 (8 £2)
35 (4 £1) »

Headphones output. level/impedance
Load Impedance

540 mV/SGO Q (Q 63)

A or B, Bl-WIRING 4 £2 - 16 S}
A and B 8 S2 - 16 9
Input sensitivity/impedance 1 was k9

SIN (rated power, 4 :2)
Frequency response

95 dB (110 do, IHF 66)
5 Hz-70 kHz (+0, - 3 dB)
+0 :15. - 0.5 dB (20 Hz - 20 kHz)

For (E) and (EG) areas so Hz/eo Hz Ac, 230 v
For (EB), (GN) areas 1 50 Hz/60 Hz Ac, 230 v - 240 v
For (GO) area only 50 Hz/eo Hz AC. 110 v- 127 V/220 v-24o v

Dimensions (Wx Hx D) : 430x136><344 mm
Weight ; 9.8 kg
Notes:

1. Design and specifications are subject to change without notice.
Weight and dimensions are approximate

2. Total harmonic distortionlis measured by the digital spectrum
analyzer. .

AWARNING , 7
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 service information by anyone else could result in serious injury or death,

A Technics®

© 1995 Matsushita Electric industrial Oo.. Ltd,
All rights reserved, Unauthorized copying
and distribution is a violation of law.

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SE-A900$ i
I Contents

Before Repair .......
Protection Circuitry ..
Accessories ..........
Caution for AC Mains Lead
Connecting the Audio Compon s ..............
Connecting the Speakers and Power Supply ..
Front Panel Controls
Listening to Sound
Recording ..

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to
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I Before Repair

. Operation Check and

Main Component Replacement Procedures .
Measurements and Adjustments
Schematic Diagram...
Printed Circuit Board Diagram.
Wiring Connection Diagram.
Block Diagram...........
Replacement Parts List
Cabinet Parts Location.
Packaging ..

(1) Turn off the power supply. Using a 10 9,10 W resistor, connect both ends of power supply capacitors (C701, C702) 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 V/240 V/l 10V -- 127 V/220V - 240V.

Power supply voltage AC 230 V

AC 240 V

AC110V-127V AC 220V-240V

160 ~ 320 mA

Consumed current'50 Hz

160 ~ 320 mA

310 - 620 mA 160 $~ 320 mA

I Protection Circuitry

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

0 No sound Is heard when the power is switched ON.
I Sound stops during a performance.

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

If this occurs, follow the procedure outlined below:
1. Switch OFF the power.

2. Determine the cause of 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.

I Accessories

0 AC power supply cord
(E. EG, GC) areas : (RJAOOtQ-ZK) ...... 1

0 Stereo connection cable
(SJP2276) ..................................... 1

0 Remote contmI transmitter 0 Batteries

(RAK-SUi BOWH) ........................... 1

(EB) area : (VJAD_733) ..

0 Amplifier connection cable

(RJL6D001510) ............................. 1

(GN) area : (RJAODSE-K) .

' Power plug adaptor [for (GO) area only]
(SJP5213-2) ............................................ 1

,1

@l

(UM-4, "',AAA R03) ................................... 2
Note: These are available on sales route.

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Page 15

I Schematic Diagram

Page
MAIN CIRCUIT .............................................................................................. 16~19
E SP. SWITCH CIRCUIT ....... *
HEADPHONES JACK'CIRGUIT ................................................................... 19
5] POWER SWITCH CIRCUIT ............................................................................ 19
E LAMP (RIGHT) CIRCUIT... 19
LAMP (LEFT) CIRCUIT ......... 1g
POWER TRANSFORMER CIRCUIT ..................................................... 19, 20
III POWER SUPPLYCIRCUIT ................................. ' ..................................... 19,20
|| VOLTAGE ADJ. CIRCUIT [1 ,1 (ac) area 0.1m ................................................. 20

I This schematic diagram may be modified at any time with the development of new technology.

Notes:

0 $2 : Voltage adjustment switch in "220V-240V" position [for (GC) area only]
0 $801 : Power STANDBY (D ION switch iPOWER, STANDBY (D ION)

O 5802 : Speaker select switch (SPEAKERA)

i

0 $803 : Speaker select switch (SPEAKEFlgfi)
O VHSOB : Power meter adjustment VFt (L ch)
I VHS) 2 Power meter adjustment VR (Ft ch)

SE-ASDOS

0 Voltage values and waveforms are measured 1as indicated in the Schematic diagram when test points between TP701 and. and

between TP703 and-are shorted. !

0 Indicated voltage values are the standard valu
taken as standard. Therefore. there may exist
No mark: Power ON

0 Voltage and signal line

: Source Signal Line

1:1,: : Positive Voltage Line
:E::-��;::- : Negative Voltage Line

0 Important safety notice:
Components identified byA mark have speCI
Furthermore. special pans which have purpos
Used. When repiacing any of components. be

0 Caution!
10 and LSl are sensitive to static electricity.

al characteristics important for safety.

Secondary trouble can be prevented by taking[

care during repair.

Cover the parts boxes made of plastics with aluminum foil.

Ground the soldering iron. :

Put a conductive mat on the work table. .

Do not touch the legs of IC or LSl with the fingers directly.

-15-

es for the unit measured by the DC. electronic circuit tester (high-impedance) with the chassis
some errors in the voltage values. depending on the internal impedance of the DC circuit tester.

es of fire-retardant (resistors), high-quality sound (Capacitors), low-noise (resistors), etc. are
sure to use only manufacturer's specified parts shown in the parts list.