Adjustments; Fm Tracking - Pioneer SX-3800 Service Manual

8 . A D J U S T M E N T S
8 . 1 F M T U N E R
FM Tracking
r Connect the SIGNAL meter or DC
between R100 (no.? pin of Q8) on
assembly and ground.
r The 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 blades of each of these tun-
ing capacitors are to be extended outwards with
spatula (Part No.GGK-066) as shown in Fig.8-1.
Spatu I a
( G G K . 0 6 6 )
f i e 1 6 1 g l s d s -
F i g . 8 - 1 A d j u s t m e n t o f t u n i n g c a p a c i t o r
Set up the test equipment as Fig.8-2.
Set the FM MUTING switch to OFF, and
FUNCTION switch to FM.
Tune the SX-3800 dial 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 (100Vo modulation).
Adjust the TC1 (OSC trimmer) to obtain maxi-
mum deflection of the signal meter.
Then tune the dial pointer to 90MHz, and set
the FM SG output frequency to 90MHz.
Adjust the core of L8 (OSC coil) to obtain
maximum deflection of the signal meter.
R e p e a t s t e p s S - 6 a b o v e .
8. Set the FM SG output level to 20 - 30d8, and
adjust TCz (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
between no. 8 and no.9 terminals on the tuner
assembly is reduced to DC 0V.
11. Set the FM SG output level to 60dB and out-
put frequency to 9BMHz, and fine tune the
SX-3800 to 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 above until both require-
ments are satisfied.
1.4. Reset the step 11" again.
15. Adjust the VR2 so that the 5-point SIGNAL
indicator reads 5.
16. Set the FM SG output level to 20d8, and turn
the FM MUTING switch to ON.
L7. Adjust the VR1 to the point where the mutins
is operated.
Multiplex Decoder
I Connect the MPX SG (FM multiplex generator)
to the extemal modulator terminals of FNI SG,
thereby using FM SG as extemal modulation.
1. Set the FM SG output frequency to gBIVIHz,
output level to 60dB (unmodulated), and tune
the SX-3800 to this frequency.
2. Adjust the VRb to obtain a 76kWz signai at
no.7 terminal on the tuner assembly.
3. Set the MPX SG modulation output to pilot
signal (19kHz) only, and set the FM deviation
of ?.5kHz (107c modulation).
4. Adjust the VR4 to obtain minimum leakage of
the 19kHz pilot signal at the REC terminal.
5. Raise the FM SG output level to 80d8, and set
the MPX SG to Main lkHz (L+R), 6?.5kHz
deviation (907o modulation), and pilot signal
to 7.5kHz deviation (107o modulation).
6. Adjust the T1 core to within tg0" to obtain
minimum distortion in the dernodulated out-
put (REC terminal).
voltmeter
the tuner
I
t
t
H
t
I
t
t
t
t
t
t
t
I
;
t
il
t
rl
arrrrTl!
U'LIFIP
/ n l l n l l
/ llll llll
X
ffi
X
1 .
2 .
i J .
5 .
6 .
q
, .
B o t o r b l a c l e