Akai AS-8100

4.
OUTPUT
TERMINATION PAD
{MODEL MR-201I0) TERMINAL
FM SIGNAL GENERATOR
(MODEL MSG-2786)
DISTORTION METER
| OSCILLOSCOPE
- (MODEL 760C)
Fig. 9
fs
FM TUNER TRACKING ADJUSTMENT
(See Figs. 7 and 8)
Use the same instruments as in item 3 (Fig. 8) and
connect them in the same way.
1)
2)
4)
5)
Set the FM Signal Generator frequency to 98 MHz
(400 Hz, 75% internal modulation) and the output
to 16 dB.
Set the Tuning Dial to receive the 98 MHz signal.
Adjust core “IF’’ of coil in front end so that the
distortion meter level is maximum and the dis-
tortion factor is less than 0.3%.
Set the FM Signal Generator frequency to 106
MHz and set the tuning dial to receive the 106
MHz signal. Adjust Trimmer Condensers “TCA”,
“TCR 1” and “TCR 2” in the front end so that
the distortion meter level is maximum and the
distortion factor is less than 0.3%.
Set the FM Signal Generator frequency to 90 MHz
and set the tuning dial to receive the 90 MHz
signal. Adjust cores “LA”, “LR 1” and “LR 2” in
front end so that the distortion meter level is
maximum and the distortion factor is minimum.
Repeat items 1) through 4) two or three times
until perfect tracking and maximum reception
sensitivity is obtained at 90 MHz, 98 MHz, and
106 MHz.
Note: When the distortion factor is 0.3%, the generator
3.
1)
output level is less than 16 dB.
MUTING SENSITIVITY ADJUSTMENT
(See Figs. 9 and 10)
Set the Signal Generator output level to 26 dB (+3
dB) and connect this output to the FM Antenna
Terminal of Model AS-8100 through the termi-
nation pad, and connect the vertical input of the
Oscilloscope as well as the distortion meter input
-to Terminal (8) (AF Output) of AM IF PC. Board.
3)
4)
2)
4)
Fig. 10
Turn Muting Level Adjustment Semi-Fixed Re-
sistor VR-1 (68 KB) in FM IF P.C. Board fully
clockwise and set FM Mute Lever to “Off”
position.
Turn semi-fixed resistor VR-1 counter-clockwise
to position at which Oscilloscope sine wave-
form is completely erased (do not turn beyond
this point).
If in this waveform erasing process, the waveform
is not erased and appears as in Fig. 10, the mute
circuit is defective. .
If perfect adjustment cannot be made by adjusting
muting sensitivity volume VR-1, because this is
due to poor alignment of Coil ““L,” (05M-755), in
the mute circuit, adjust the core of “L,” for
improved mute circuit sensitivity.
TUNING INDICATOR CHECK AND
DISTORTION ADJUSTMENT
Use the same instruments as in Section 5 (Muting
Sensitivity Adjustment) and connect them in the
same way.
Set the FM Signal Generator Output to 66 dB, and
connect this output to the FM Antenna Terminal
of Model AS-8100 through the termination pad.
Connect the Oscilloscope Vertical Input as well as
the Distortion Meter Input to Terminal (8) (AF
Output Terminal) of FM IF P.C. Board.
Set the FM Signal Generator frequency to 98
MHz, and set the tuning dial of Model AS-8100 to
the same 98 MHz frequency.
Adjust the upper core of “Ly” (O05M-775A) so
that the tuning indicator needle is centered, and
adjust the lower core of “L,” to obtain the least
distortion.