Sharp SC-103H Service Manual page 16

7. PLAYBACK AMPLIFIER SENSITIVITY CHECK (Refer to Fig. 39)
Oscilloscope
Attenuater
R/P HEAD PLAY BACK mode
Speaker
Jack
Oummy
Figure 39
Set Mode Selector Switch (SW-8) at "CASSETTE PLAY".
Set VOLUME Control (R207, R208) in the maximum position, BASS Control (R209, R210) and TREBLE Control
(R211, R212) in the central position.
Set the unit at PLAYBACK mode.
Disconnect the ground lead wires (red) of Record/Playback head for both channels. Input 1kHz signal between
head terminal and lead wire.
Connect 8 ohm (£5%, 10W) dummy resistor to Speaker Jack (SO704, SO705)
PLAYBACK AMPLIFIER sensitivity is normal if attenuator's reading is -78 dB to -84 dB when voltage at both
ends of resistor becomes 3.3V.
8. PLAYBACK AMPLIFIER FREQUENCY CHARACTERISTIC CHECK (Refer to Fig. 39)
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Set Mode Selector Switch (SW-8) at "CASSETTE PLAY".
Set BASS Control (R209, R210) and TREBLE Control (R211, R212) in the central position.
Set the unit at PLAYBACK mode.
Disconnect the ground lead wire (red) of Record/Playback head for both channels.
Input 1kHz, -81 dB signal between head terminal and lead wire.
Connect 8 ohm (45%, 10W) dummy resistor to speaker jack (SO704, SO705) and adjust VOLUME Control (R207,
R208) so that voltage at both ends of resistor becomes 0.2V.
Then change the frequency of signal generator to 63Hz and 8kHz, and if deviations to 0.2V are +13.5 dB to
+19.5 dB and +1 dB to -5 dB, respectively, the PLAYBACK AMPLIFIER frequency characteristic is normal.
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