Sharp GF-6060H - Page 6

EXPLANATIONS OF APSS AND ALC
= APSS
The APSS circuit employed for the GF-6060H and
GF-6060E is a little different from that for the con-
ventional models — the level comparator (Figure 6) is
comprised instead of the limiter and Schmitt.
Let’s explain the behaviors of the new APSS.
1. The signal coming from the head is boosted by the
equalizer (1C101) amplified first and next by the level
amplifier (Q102), then it enters pin of the level
comparator (1C102).
2. The level comparator works to make the LEDs D102
(1 to 5) light according to a variety of the input. level,
which is shown:
LED No. /D102—11D102—2/D102—3|D102—4/D 102—5
Level (dB)
The unit is designed to provide VU indication for
both the tape playback mode and the radio reception
mode, and in addition, that indication is allowed in
the APSS mode via the said level comparator function,
the feature of which is here explained:
Even if the recording level of a tape is relatively low
(—30 dB), it is boosted by the level amplifier (Q102)
to permit the VU indication — in this case, the D102—1
can light assuming that the recording level is within
the range from —30dB to —40dB.
ANOTHER
CHANNEL
TIME
CONSTANT
Ccl49
RI64,RI65
When the programs space is reached in playback, no
voltage is applied to the D102—1 for it not to light
at all.
. For the non-signal recorded part which exists for not
more than 0.5 second, it shall not be mistaken as the
programs space, and this is made possible via the time
constant assured by the capacitor (C146, C149) and
resistors (R164, R165).
. When the APSS switch is placed at ‘‘ON”’ the transistor
Q105 of the APSS circuit turns on first, and then
the operation goes on as follows. See Figures 7—1
thru 7-4.
1) When the unit is in the playback mode with the
APSS switch kept off, the Q104 and Q105 remain
off — though the C152 is charged (shown in Figure
7—1), so that both the Q106 and the plunger be off.
2) The Q104 turns on or off according to whether
or not a voltage is present at the D 102—1 (see
Step 2), and this is summed ‘up;
Recorded Voltage at
program D102—1 Gules
Absent Absent OFF
Present Present ON
POWER AMP
VOLUME
LEVEL
COMPARATOR
SWITCHING
PLUNGER
DRIVE PLUNGER