Scott 387B Service Manual

Page 1

NOTE:

II. II. Scott 3873

FOR REPLACEMENT PART NUMBERS, REFER TO SCHEMATICS

10.7MHZ

FIG. I

10.7MHZ
VV

FIG. 2

ALIGNMENT INSTRUCTIONS

CAUTION: Use isolation transformer or observe polarity when connecting test equipment.

Maintain line voltage at lZOVAC.

Allow a 15-minute warmiup period.

Use only enough generator output to obtain a suitable indication.

AM ALIGNMENT-SELECTOR IN AM POSITION

Connect generator across loop fashioned of several turns of wire.

Set volume at maximum.

GENERATOR RADIO DIAL

FREQUENCY SETTING INDICATOR ADJUST REMARKS

4SSkHz Tuning gang Output meter T302, T301 Adjust for maximum. Repeat until
400-hertz fully open across voice coil no further improvement is noted.
Modulation

600kHz Tune to signal " T203 Adjust for maximum.

1640kHZ " " C232 Adjust for maximum.

14UOkHz " " C225

Adjust for maximum. Repeat AM alignment
until no further improvement is noted.

FM IF ALIGNMENT USING AM SIGNAL GENERATOR-SELECTOR IN FM POSITION

High side of generator thru .001mfd to pointht L205 6: R203

low side to ground.

common to ground.

GENERATOR RADIO DIAL

FREQUENCY SETTING INDICATOR ADJUST REMARKS
10.7MHZ Point of non~ DC probe of VTVM T301 (Fri), Adjust for maximum.
Unmodulated interference to Cathode 0306, T20]

DC probe of VTVM
to Jct R3125R314
common to ground.

T301 (Sec)

Adjust for zero reading.
or-negative reading will be obtained
on either side of correct setting.

A positive

Page 2

ALIGNMENT INSTRUCTIONS (Continued)

FM IF ALIGNMENT USING FM SIGNAL GENERATOR-SELECTOR IN FM POSITION

High side of generator thru .Oolmfd to point Jct L205 6 R203
Use only enough marker signal for indication.

low side to ground.

Use 60-hertz frequency modulated signal

with 450kHz sweep. Use 60-hertz sawtooth voltage in scope for horizontal deflection.

0306, low
side to ground.

GENERATOR RADIO DIAL REM

FREQUENCY SETTING ND'CJOR ADJUST ARKS

10.7W-Iz Point of non- Vert input of T301 (Fri), Disconnect stabilizing capacitor C323
450kHz Sweep interference scope to Cathode T201 Adjust for maximum gain and symmetry

of response similar to Fig. l with
markers as shown. Reconnect C323

Vert input of
scope tDJCt R312
.3 R318 low
side to ground.

T301 (Sec)

Adjust T301 (Pri) to place marker
center of S curve similar to Fig.
Readjust T301 (Sec) for maximum
amplitude and straightness of line.

FM RF ALIGNMENT-SELECTOR IN FM POSITION

Connect generator across antenna terminals with lZO-ohm carbon resistor in series with each lead.
Adjustment of coils by bending should not be attempted unless the coil is deformed or replaced.

GENERATOR RADIO DIAL
FREQUENCY SETTING INDICATOR ADJUST REMARKS
MHZ Low freq end DC probe of VTVM L206,LZOS,L201 Adjust for maximum.
Unmodulated to Cathode D306
common to ground.
108MHz Tune to signal " C217,C212,C203 Adjust for maximum. Repeat FM RF steps
Unmodulated

until no further improvement is noted.

FM STEREO MULTIPLEX ALIGNMENT USING FM STEREO SIGNAL GENERATOR (t .DOOI% ACCURACY)

High side of generator thru 47K to point Jct. R312 5. R318

low side to ground.

312%??ch INDICATOR ADJUST REMARKS
67kHz Vert input of scope thru 47K to L503 Adjust for MINIMUM.
Base (2506, low side to ground.
19kHz Vert input of scope thru 47K to LSO4,L505 Adjust for maximum.
Cathode 0501 low-side to ground.
19kHz Vert input of scope thru 47K to T501 Adjust for maximum 38kHz response.
Cathode 0506 low side to ground.
Modulated Vex-t input of scope to point R536 Adjust for MINIMUM. This step
Left Channel R low side to ground. should require only slight adjustment.
Modulated Vert input of scope to point R532 Check for MINIMUM. If necessary, make
Right Channel L low side to ground. compromise adjustment of R536