HH SCOTT Scottie 2550 Stereo Receiver Owner’s Manual

HH SCOTT Scottie 2550 Stereo Receiver Owner’s

AUDIO SECTION

EQUIPMENT NEEDED
Audio Oscillator VTVM Oscilloscope Triplett VO:M Load
Attenuator Distortion Meter Variac
AC Supply Fixture 12 Volt Supply DC

Set Controls to the Following:

• Balance Pot
  Flat “O”

• Input Selector
  Phono

• Tone Controls
  Flat “O”

• Loudness
  Min.

• Speaker Switch
  ON

• Power Switch
  OFF

• Tape Switch
  Normal

Preliminary Visual Inspection and Continuity Checks
Inspect unit for defects such as broken wafers, loose stand-up resistors, cracked terminals and jacks, loose transformer bolts, and other such defects. See trans­istor precaution list. Check production tag for necessary inspectors’ stamps. Shake unit to free all scrap wire pieces.

1. Voltage Checks
   Check power supply +17 to 19 volts.

2. Sensitivity Check
   Audio osc. to TAPE IN, tape switch to MONITOR at 0,25 (*2 dB) input, Connect oOnm Load to main spea ker taps, Turn loudness pot to max. , observe output of 2 wattts (5 V). Check tape Output jack with troubleshootin8 lead tor same autautt as ianal

3. Distortion Check
   Distortion at 3V output, 1.5% max.

4.  Speaker Switch and Phone Jack Check
   Speaker switch to OFF pos. Note complete loss of signal. Loudness to min. Insert phone plug into phone jack, remove speaker leads and connect to phone plug. Loudness to max. Note drop of 26 !2 dB.

5. Loudness Volume
   Adjust attenuator for O dB on 1 volt range.
   osi• to 1000 Hz, vol. pot to 4 flat. Switch osc. to 100 Hz; note rise of 7 _2 dB. Switch osc. to 10 kHz; note reading of O .:t2 dB.

6. Tracking
   In TEN dB steps check tracking of volume pot in L & R channels. Output
   may be no more than 3 dB between channels down to -40 dB.

7. Crosstalk
   Left channel at 1 kHz, full output 4 V. Turn Bal. pot to “L”, note no drop in output. Bal. pot to “R”, note 45 dB drop in output. With input and out­put in Right channel., no drop in “R” pos. and 45 dB drop in “L” pos. of pot. Attenuate to obtain O dB on l volt scale.

8. Tone Controls
   Bass
   Boost –ro-dB +2 dB Cut – 10 dB ±2 dB
   10 kHz
   Treble Boost – 10 +2 dB Cut … 14 +2 dB

9. Frequency Response Check
   With output O dB on 1 volt range, sweep osc. from 100 Hz to 10 kHz. Note no more than 2 dB variation in output.
   Low
   3 dB pt. 100 Hz or lower
   High
   3 dB pt. 10 kHz or higher

10. Regulation Check
    At 1 kHz O dB 1 V range remove 8 ohm load. Output rise of 1 dB max.

11. Preamp Gain Check@ 1 kHz
    Attenuate input 36 dB, input leads to phone. Output O dB 1 V range + .:..Z dB.

12. Preamp Frequency Response Check

13. 1 kHz
    0 dB (ref)

14. 10 kHz
    -13 +2 dB

15. 100 Hz
    +13 =f2 dB

16. Hum Checks
    Position    Loudness Pot    Max Hum
    Tape In     10    5 mV
    Tape In    0  5 mV
    Phono (Inputs shorted)    10    30 mV

17. Repeat Steps 2 through 13 for Right Channel.

AM SECTION

Pre-Test

1. Switch tuner to AM position, output from tape output jack.

2. Couple signal generator at 455 kHz to AM section of IF. Clip ground lead to  chassis.

3. Peak IF 1 s and detector for max. audio noise output, using no modulation. Final peaking should be done with 20 uV from generator with output level of 100 mV 2 dB.
   Final Test

4. Remove signal generator coupling to IF’s, connect generator to loop antenna cold side. The cold side of loop is closest to input jacks.
   Calibration

5. Tune oscillator coil to 600 kHz and oscillator trimmer to 1600 kHz.
   Sensitivity

6. Tune RF trimmer at 1400 kHz with a very weak signal for a peak. Be sure antenna leads are dressed properly.

7. Repeat Step 5 until unit is aligned and max. output at given frequencies has been achieved. Final calibration tracking check:
   WEEI    WHDH    WBZ    WMEX
   590 kHz  10 kHz     850 kHz   20 kHz 1030   t20 kHz  1510 (tol  20 kHz)

8. With 10 uV minus 2 dB input•attenuation, output should be .25 to .40@ 600 kHz and 1400 kHz.

9. With phones, check for AM calibration, oscillation, harmonic pickup, etc. All output measurements are taken at 60% modulation.

TONE corfl-Rol PRE AMP

EgUIPMENT NEEDED

VTVM Oscilloscope
VOM Distortion Meter
Fl1 Generator (or source)
MX Audio Generator Generator (or (or source) source)
Set Controls to the Followin:
Input Select. Switch

PRELIMINARY CHECKS

loose Inspect trunit ansformers, for defects binding such tuning as broken condenser, wafers, broken cracked components, terminals, lead and dress, jacks,
scrap ulator; sockets.in unit, etc. Make certain all transistors are firmly seated in at correct Reg­
shouTake ld output measure from +10 :!:1 V, tape-out and 17 jacks. V .!2 V Turn for unit stereo on, check light supply.voltage

1. Mono Alignment and Sensitivity Check
   Front End and IF Alinment
   With about 10 uV generator output, align and peak front end for max. align output.
   With detector 3 uV bottom input, slug align for IF’s max. for audio max. and audio. top slug With for 1 or min. 2 K uV distortion.input,

2. Sensitivitr and Distortion
   For Measure sensitivity sensitivity check, of an tuner electronic with 7 uV 19 RF kHz input. and 38 Must kHz filter obtain 30 may dB be usableused.
   maxsensitivity distortion at 92 of and 0.8%. 106 MHz. Audio output Recheck spec. distortion, at lK, lK 0.5 uV to 1.0 input. volts. 400 Hz – e
   De-Emehasis Check
   Tune to 90 MHz (modulation of 8.2 kHz), note decrease of 12 ±2 dB in output.
   Calibration Check
   Check calibration against stations – max. tolerance 200 kHz.

3. multiplex Alignment
   the With a multiplex composite alignment stereo will signal be as from follows: generator or source connected to the unit,

4. 67 kHz Aliiinment
   Using an RF signal modulated with 67 kHz, note output taken directly from the multiplex (either pin located adjacent to the PEC 312). With signal applied, adjust the LV015 (67 kHz trap) for lowest possible reading on VTVM ..

5. 19 kHz and 38 kll Alnment
   With a low capacity scope probe connected to the base of Q2 (first QA15), adjust first pilot can (next to AM det. can) for max. output. After the first pilot
   can has been adjusted, move scope probe to the base of Ql (SE1990) and adjust
   the second pilot can (directly behind AM section of front end) for max. output. The 38 kHz alignment can be done with the scope probe at any one of the four
   demodulator diodes surrounding the TRV.038tt can. Peak the 38 kHz can for max. output as was done to the others.
   Separation has been preset by a resistor divider; therefore, the spec. is:
   Separation
   L:-00 Hz

   • 20 dB min. without filter
   • 25 dB min. with filter
     Any difference in channels gre3ter than 3 dB can be brought within spec. by
     detuning one of the pilot cans slightly, thereby equalizing the separation.

6. Listenin Check
   Check unit for ac short, calibration, oscillations and hum. Connect a 12 volt de source to the blue conn.ector plug on the rear and switch Power Switch to
   OFF. Listen to the unit and observe that it operates well on 12 volts, as well as 117 ac.,

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