NAD 1700 - FM Alignment Procedures - Part 1; Necessary Alignment Equipment; Pre-Alignment Notes; FM Local Oscillator Tuning

FM ALIGNMENTS
NECESSARY INSTRUMENTATION
e Stereo Modulator (less than 0.05% THD, more than 50dB Sep.)
@ FM Generator (less than 0.05% THD)
e 75 ohm Dummy Antenna (if needed by generator)
® Audio Oscillator (not necessary if FM Generator has built-in sweep, e.g., SOUND TECHNOLOGY ST 1000A or
ST 1020A)
@ 2 AC VTVM's (or one with a Left/Right switch)
@ THD Analyzer (resolution less than 0.1%)
® Oscilloscope (5mV or better sensitivity, X-Y capability)
e Frequency Counter
e Detector Probe
IMPORTANT NOTES
1) RF levels are at antenna input.
2) Before alignments commence, switch off IF NARROW, FM NR and MONO; select FM.
3) If FM Generator is not synthesizer-type, be sure to check its frequency with Frequency Counter when
adjusting detector and multiplex decoder circuits.
4) Hum in measurements may be caused by ground loop via antenna cable; if so, use isolation balun, or isolate
cable shield and hot with small capacitors (470~ 1000pf).
To adjust front-end coils, bend gently with wooden or plastic tool (non-interactive).
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A. FM LOCAL OSCILLATOR FREQUENCY
1. Connect Frequency Counter between TP-107 and Ground.
2. Tune to 90 MHz (No RF input needed).
3. Adjust C-278 so that reading is 100.700MHz +/— 2kHz.
B. FRONT-END ALIGNMENTS (should only be necessary after repair to front end).
TUNING VOLTAGE
1. Connect DMM between TP-101 and Ground.
2. Tune to 88.00MHz, and adjust L-6 if reading is not 3.2V +/— 0.5V.
3. Tune to 108.00MHz, and check that reading is 22.5V +/— 1.5V.
4, Repeat above steps 2 and 3 until within tolerance.
TRACKING
1. Connect FM Generator to 75 ohm antenna input (modulate +/— 150kHz sweep) and Detector Probe to
Pin 1 of IC-103 (ground to tunershield).
2. Adjust vertical sensitivity of Oscilloscope to maximum, and set to X-Y mode. (X input is sweep signal,
Y is detector probe).
3. Set tuner to 105MHz, enter into Preset 2, and adjust generator so that curve appears on Oscilloscope, and
covers approximately 1/2 of display.
4. Adjust C-2, C-10 and C-12 for maximum curve height, while reducing FM Generator output, if necessary,
to keep entire curve on display.
. Set tuner to 9OMHz, enter into Preset 1, and adjust Generator so that curve appears on Oscilloscope.
. Adjust L-2, L-4 and L-5 for maximum curve height.
7. Repeat above steps 3, 4, 5 and 6 (use Preset 1 and 2) until both curves are at maximum height.
Note: 105MHz curve is typically slightly higher than 90MHz.
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Oo ol
Cc. IF ADJUSTMENTS
1. Set tuner to approximately 98MHz (must be an unoccupied frequency), and adjust FM Generator to
display curve on the Oscilloscope.
2. Adjust L-8 and L-101 for maximum and symmetrical curve using as little RF input as possible.