Pioneer SX-3800 manual t t t t t t, ffiULIFIP, Adjustments, n l l n l l / llllllll, arrrrTl

8 . ADJUSTMENTS

8 . 1 F MT U N E R FM TrackingrConnectthe SIGNAL meter or DC voltmeterbetweenR100 (no.? pin of Q8) on the tuner assemblyandground.

rThe tuning coil in the RF amplifier circuit does not have an adjusting core. Consequently, tracking adjustment at 90MHz are performed by regulating the gap between rotor and stator of

the tuning capacitor (VC3). The expression "adjust VC" found in the text means that the two outer rotor bladesof eachof thesetun- ing capacitorsare to be extended outwards with spatula(Part No.GGK-066)asshown in Fig.8-1.

Botor blacle

SpatuIa

( G GK . 0 6 6 )

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Fig . 8 - 1 Adjustmentof tuning capacitor

1 . Set up the test equipmentasFig.8-2.

2 . Set the FM MUTING switch to OFF, and FUNCTION switch to FM.

i J . Tune the SX-3800dial pointer to 106MHz.and set the FM SC (FM signal generator) output frequency to 106MHz, output level to 60d8, modulation frequency 400H2,frequency devia- tion 75kHz (100Vomodulation).

Adjust the TC1 (OSC trimmer) to obtain maxi- mum deflection of the signalmeter.

5 . Then tune the dial pointer to 90MHz, and set the FM SG output frequency to 90MHz.

6 . Adjust the core of L8 (OSC coil) to obtain maximum deflection of the signalmeter.

q, . RepeatstepsS - 6above .

8.Set the FM SG output levelto 20 - 30d8, and adjustTCz (ANT trimmer) and TC3 (RF trim- mer) at L06MHz, and L2 (ANT coil) and VCB

(RF tuning capacitor) at 90MHz in the same manner as described above in steps 3 - ?.

These adjustments will ensure optimum sensi- tivity in the 90MHz - 106MHz range, and minimum difference in sensitivity between the two extreme frequencies.

9.Retune the dial pointer to a position with no

input signal.

10.Adjust the N core of T2 so that the voltage betweenno. 8 and no.9 terminalson the tuner assemblyis reducedto DC 0V.

11.Set the FM SG output level to 60dB and out- put frequency to 9BMHz, and fine tune the SX-3800to this position.

12.Then rotate the D core of "t2 to obtain mini- mum distortion in the demodulated output (REC terminal)to minimum.

13.Repeat steps g - 12 aboveuntil both require- ments are satisfied.

1.4.Resetthe step 11"again.

15.Adjust the VR2 so that the 5-point SIGNAL indicatorreads5.

16.Set the FM SG output level to 20d8, and turn the FM MUTING switch to ON.

L7. Adjust the VR1 to the point wherethe mutins is operated.

Multiplex Decoder

IConnectthe MPX SG (FM multiplex generator) to the extemal modulator terminalsof FNI SG, therebyusingFM SG asextemal modulation.

1.Set the FM SG output frequency to gBIVIHz, output level to 60dB (unmodulated),and tune the SX-3800to this frequency.

2.Adjust the VRb to obtain a 76kWz signai at no.7 terminalon the tuner assembly.

3.Set the MPX SG modulation output to pilot signal (19kHz) only, and set the FM deviation of ?.5kHz(107cmodulation).

4.Adjust the VR4 to obtain minimum leakageof the 19kHz pilot signalat the REC terminal.

5.Raisethe FM SG output levelto 80d8, and set the MPX SG to Main lkHz (L+R), 6?.5kHz deviation (907o modulation), and pilot signal to 7.5kHz deviation(107omodulation).

6.Adjust the T1 core to within tg0" to obtain minimum distortion in the dernodulated out- put (REC terminal).

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