Scott 2506 2507 Service Manual

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PRICE 1.00

SERVICE MANUAL
FOR
2§-0§/07 COMPACT

Scott . . . where innovation is a tradition

N. M. Scott. Inc. 111 Powdermili Road, Maynanl. Mass., 01154

FORM 029-1175-022 COPYRIGHT H. H. SCOTT, INC. 1969

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AUDIO SECTION

AUDIO SECTION
TEST

Set Controls to the Following:

SP-2 OFF

Input Selector Extra

Mode Switch Stereo

Tone Controls Flat 0"

Loudness Full CCW

Vol. Comp. Loud

Sp-l ON

Balance Pot. 0"

Power ON

1. Offset, Bias and Voltage Checks

3a.

Check main supplies for +17 volts and -17 volts :10%. At the emitter of the QP-11, on the main chassis,
check for 12 VDC.

Bias measurements are to be made with meter directly across either .82 ohm resistor on driver board. Adjust
bias pot (pot nearest rear panel) for .6mA.

Sensitivity Check

Audio osc. to EXTRA at .40 (+2 dB) input. Connect 8 ohm load to SP-1 jacks. Turn loudness pot to max.,
observe output of 16.1W (8V). Check tape output jack with trouble-shooting lead for same input signal as
above.

Distortion Check
At 8V output max. distortion 0.6% @ 400 Hz.
Balance Pot

With input and output connected to left channel, note loss of 0 dB when pot is rotated to L" position. When
pot is rotated to "R", note a 45 dB drop in output. With input and output in the right channel, pot rotation
to R" will indicate no drop in output, and in "L" position a 45 dB drop will occur.

Tape Monitor Switch Check

Audio osc. to EXTRA at .40v input to L channel. Note output at left channel speaker terminal. Put tape
monitor switch in the IN position. Note loss of output. Connect jumper cable from L channel tape OUT to L
channel tape W. Note restoration of signal out. Repeat process for R channel, then return tape monitor switch
to OUT position.

Speaker Switch 8i Phone Jack Check

SP #1 switch to OFF position. Note complete loss of signal. Loudness to min. Insert phone plug to phone
jack, remove speaker leads and connect to phone plug leads. Loudness to max. Note drop of 26 :2 dB. Switch
# 1 speakers in. Return speaker leads to output iacks. Note restoration of signal. 8 ohm load to speaker #2
jacks. Speaker 9% 1 switch OFF, speaker #= 2 switch 0N, note same output as 7% 1 speakers. With speaker # 1
and speaker #2 switches ON, note drop in output of 1 to 2 dB. Return speaker switch to speaker #1 ON and
speaker # 2 OFF and load to speaker #1 jacks.

Loudness Volume Check

Loudness vol. sw. to LOUD pos. Loudness pot to 4 flat pos., osc. to 1 kHz. Take ref. Osc. to 100 Hz. Note
rise of 7 :2 dB. Loudness vol. svv. to VOL. pos., osc. to 1 kHz. Take ref. At 100 Hz and 10 kHz note 0:2 dB
from original ref. Loudness pot to max., osc. at 1 kHz, output 8V. Loudness pot to min. Note drop of 70 dB.
Loudness pot to max.

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AM-FM FRONT END (100-1330-017)

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TUNER SECTION

Set Controls to the Following:

Separation Pot Max CCW
Input Select. Switch FM

PRELIMINARY CHECKS

Make certain all transistors are firmly seated in correct sockets. Take output from Tape Out jacks.
1. Mono Alignment and Sensitivity Check

Front End and IF Alignment

With about 10 uV generator output, align and peak front end for max. output. With 1 or 2 K uV input, align
detector. Botton slug for max. audio output and top slug for min. distortion and perfectune light to light.

2. Sensitivity and Distortion

Measure sensitivity of tuner with 3 uV rf input. Must obtain 30 dB usable sensitivity at 92, and 106 MHz.
Recheck distortion, 2 K uV input. 400 Hz - max. distortion of 0.8%. Audio output spec. at 1 K 1.5 to 2.5 V.

3. FM Hum Check
Tune to 91.5 MHz, measure min. of 55 dB (may reverse ac plug), unmodulated carrier.

De-emphasis Check
Tune to 90 MHz (change mod. to 8 kHz), note decrease of 12 i 2 dB in output.

Calibration Check
Check calibration against stations - max. tolerance 1.2 MHz.

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