Infrared Receiver - Loewe Q2500B Serviceanleitung

Technology of Q 2500 colour TV set
After switching to the service mode, chassis
tuning is implemented with the FB transmitter.
The service mode is called up by pressing the
functional button "?" four times, so that the
"Service" display appears, and then pressing
the "M" button on the remote control within
one second. Then using the curser buttons,
the individual tuning functions can be called
up. Tuning is also carried out using the cursor
keys. The data is initially stored in the working
memory C 161 and is only transferred to the
memory on operation of the "ok" memory but-
ton. Once returned to normal FS operation,
use the "E" button to return to remote opera-
tion.
Pressing the Z 1 button switches the remote
control processor to another mode. This
means that the transmitter can be used for
both a videorecorder and DVD player from
Loewe. For the videorecorder, however, con-
trol is only possible with Korythso code, as
used by Panasonic. For the DVD player we
use the RC 6 code.
If the remote control is not used in the video-
recorder or DVD mode for 20 sec, then it
automatically switches back to the TV mode.
The video or DVD mode is displayed for Con-
trol 10 by the LCD and for Control 150 by an
LED on pin 2 (Y1) and pin 3 (Y0).
For Control 10 the LCD is controlled from
ports Y3 to Y7. Up to Y3 these are also used
to query the button matrix.
The operating voltage is also monitored in
Control 10 and displayed correspondingly in
the LCD. Measurement of the battery voltage
is carried out by transistors Q 416, Q 414 and
Q 404 on pin 5 of 84 C 122.
Document Q 2500

4.1.2 Infrared receiver

C8216
I 8216
Infrared
reciever
The IR receiver on the local control unit is a
thick film circuit and is fully encapsulated.
The IR signal from the transmitter is converted
into an electrical signal by the receiving diode,
amplified and prepared in such a way that it is
available on the output as 2 Vss.
With the next transistor Q 8202 on the local
control unit the signal is amplified to 5 Vss. In
this way the IR decoder in SDA 6000 can be
safely controlled via pin 5
Via IC I 2716 and transistors Q 2721, Q 2731
and Q 2741 the IR signal is applied to pin 8 on
each of the three Euro sockets. This allows
hidden videorecorders to be remotely con-
trolled via the IR receiver of the television set
and the AV switching voltage line (see AV
operation).
Via Q 2823 the signal reaches transistor Q
2862 on pin connector W 1076. Via W 1076
the IR signal is supplied to a connected
online-box.
The pulse width for the RC 5 code of the re-
mote control is about. 900 µs. If a connected
Multi Media Component is operated with the
Control@media IR keyboard, the data is not
transferred with the slow RC 5 code, but with
an RC MM code (MM-Multi Media) designed
for fast data transfer. The pulse width for the
RC MM code is 167 µs.
The pulse width of 167 µs requires an IR-
receiver with a very short time constant.
Therefore, in Multi Media devices a special IR
receiver is used, which for operational pur-
65
R8216
U5SB
R8217
R8205 RC5
Q8202
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