Led-Control - Philips Pocket Memo 388 Serviceanleitung

The right hand turntable (pulse wheel) is watched by an optocoupler (OC 1). During tape
transport pulses arrive at base of TS 5 (TS 5:1, 0, 1, 0, ....), these pulses do not allow C 15
to charge; IC 1-12,13:0, IC 1-11:1.
Once the right hand turntable has stopped (no pulses), TS 5:0, and C 15 is charged via R 11;
IC 1-12,13:1, IC 1-11:0, the motor stops via D 1.
IC 1-10:0, IC 1-8:1, IC 1-5:1, IC 1c (warning tone generator) is active.
The EOT-warning tone at IC 1-6 arrives at the loud speaker via SK 2c and the amplifier IC 2.
IC 1-8:1, TS 11:1; recording signal is muted (TS 1:1) and the warning tone circuitry is com-
pleted via SK 2a, C 33 and TS 11:1.
D 14 discharges rapidly C 15 via C 48 in case of the motor starts running after the tape has
stopped in VA-mode.
During RECORD the LED-control is switched on by SK 2b.
The red record LED D 6 lights up at a battery voltage > 2.1 Volts, TS 10 conducts (the swit-
ching level is determined by the constant diode-voltage at OC 1-2), TS 9 is switched off and
D 6 is controlled by R 80.
When the battery voltage is < 2.1 Volts, TS 10 will be switched off making TS 9 conductive
and D 6 extinguishes.
IC 1c and R 13/C 9 form a generator for the warning tone, which produces 1500 Hz swit-
ched on by IC 1-5:1.
During RECORD, TS 4:1 via R 8 and SK 2b, IC 1-9:1, IC 1-10:1, IC 1-8:0, IC 1-5:0, making
IC 1c inactive.
When the battery voltage is lower than 2.1 Volts, TS 10:0, TS 9:1, D 6:0; via C 8 a positive
pulse is generated at the base of TS 4 (TS 4: 0 for approx. 200 msec.), IC 1-9: , IC 1-8:
IC 1-5: , IC 1c is active for approx. 200 msec.
The warning tone at IC 1-6 arrives at the input of the amplifier IC 2-7 via C 28 and C 43. The
speech signal is muted during warning tone, because TS 1 conducts via R 56.
IC 1-8:1, TS 11:1 via R 46; the recording signal is muted and the warning tone can be heard
in the loud speaker; this is due to the high current via LS, SK 2a, C 33, TS 11 to ground.
In PLAYBACK mode the record/playback head K 1 is connected to the pre-amplifier TS 6 via
SK 2d and C 16. Being amplified by TS 6 and TS 8 the signal arrives at pin 7 of the bridge-
amplifier IC 2 via C 21, R 31 (volume control), R 60, SK 2c and C 43. The output signal of the
bridge-amplifier at IC 2-1 and IC 2-3 arrives at the loud speaker via socket switch SK 8 and
SK 2a.
If an earphone is connected to socket SO 3, the built-in loud speaker is disconnected by
socket switch SK 8.
AC-BIAS and the record LED are switched off by SK 2b in PLAYBACK mode.
At the end of tape (standstill of the RH-turntable), IC 1-11:0 and the motor is stopped via D 1.
IC 1-11 :0, IC 1-8:1, IC 1-5:1; IC 1c is active, but the warning tone via C 28 is muted in PLAY-
BACK by TS 1:1 (via D 7, R 56).
LFH 0388/LFH 0488/LFH 0588
End of tape recognition
and warning tone

LED-control

LFH 0588/0488
Warning tone for low
battery voltage
during RECORD
LFH 0588/0488
,
Playback
15