Advent powered loudspeaker ls

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ADVENT POWERED LOUDSPEAKER
PRELIMINARY SERVICE MANUAL

Beginning with serial number 20 00100

TABLE OF CONTENTS

General Information

Required Test Equipment ................... ...... 1
Specifications ................................... 2-3
Circuit Description ............ ..... ............. 4-5
Block Diagram .......... ........ .................. B

Servicing Information

01::me

Power Amplifiers Test ........................... . 7-8
Protection Circuits Test ......................... 9

Amplifier PCB View ............................... 10
Transistor Basing Diagrams . ...................... 11
Control Panel PCB View ................... ........ 11

Parts List

WEOOMH

Amplifier PCB ..................... . ...... . ....... 12-13

Power Supply/Backplate ......... .................. 13
Control Panel PCB ....... . ........................ lu
Loudspeaker ............. . ........................ 1%
Misc. Hardware ......................... .......... 15

Required Test Equipment

The following list of test equipment is required to properly
service the Advent Powered Loudspeaker.

mummcwmu
. . . . . -

Audio Oscillator, Hewlett Packard 20HC or equivalent.
Precision ACVM, Hewlett Packard 400 CL or equivalent.
Oscilloscope, Tektronix T922 or equivalent.

Volt, Ohm Meter, Hewlett Packard Model H27A or equivalent.
Distortion Analyzer, Hewlett Packard Model 333A or equivalent.
One (1) Three Ohm Load Resistor 1%, 100 Watt Minimum Rating.
One (1) Six Ohm Load Resistor 1%, 100 Watt Minimum Rating.

AC Line Variac. General Radio W5MT3A or equivalent.

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SPECIFICATIONS
(All specs are with 120 VAC line)

Control Panel

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Maximum input signal level: 10 volts RMS 4

Hum and noise, (sensitivity control at 1v, input shorted, EQ.
controls at zero):

Woofer less than 0.1mv

Tweeter less than 0.1mv

Total harmonic distortion, (EQ. controls at zero): Woofer (lv
RMS out at l khz): Less than 0.05% THD. Tweeter (1v RMS out at
10 khz): Less than 0.05% THD. .

Input impedance: 100k ohms

EQ. gain and frequency response (sensitivity control at 0.3V,
E0. controls at zero):
Woofer +7db at 20 hz
+7db at MOO hz
Odb at 7 khz

Tweeter Odb at #00 hz
+2.5db at 3 khz
+6db at 10 khz

EQ. control cut 8 boost, (relative to mid position):
Bass, Udb/+6db at 30 hz 1 2 hz '
Treble, -udb +udb at 10 khz M
Power supply requirement: i lu VDC, approx. 7ma.
Power Amps
Hum and noise, (inputs shorted) less than 0.5mv either amplifier.
Power output, woofer amplifier: 80 watts (22v RMS into 6 ohms
load at l khz). Tweeter amplifier: 80 watts (15.5 VRMS minimum
into 3 ohm load at 10 khz). Note: The tweeter protection circuit
must be disabled for this test.

Distortion: Less than 0.1% THD, either amplifier up to 80 watts
either 3 or 6 ohms load.

VI limiting: Activates at 7.5V RMS into 2 ohms either amp.

Tweeter protection limit: Tweeter amp, activates at 9.5V RMS at

l khz, llv RMS at 10 khz, no load.

DC/Excursion limit: Woofer amp. activates at 30v RMS at 20 hz

output, no load, or +13v DC out, either amplifier, no load.

Backplate thermal limit: Activates at 75°C backplate temperature:

reset time approximately 30 seconds after shutoff in 25°C ambient.
Complete System Electronics \y

Hum and noise, (sensitivity control at 1v, input shorted, HQ

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