Av Operation - Loewe Q2500B Serviceanleitung

Technology of Q 2500 colour TV set
If an error occurs – H level on pin 94 of the
CCU - the CCU swtiches the device after 2
seconds to standby operation.

4.1.10 AV operation

The circuit is designed so that AV operation
with switching voltage on programme loca-
tions can be programmed.
Setting is implemented in the menu under
connect AV device.
The menu makes clear the exact procedure
for setting up or you can refer to the overview
in the operating instructions. Monitoring of the
switching voltage on pin 8 of the AV socket is
implemented via transistors Q 2737/Q 2726
and Q 2746 for AV1/AV2 and AV3. The three
emitter followers are connected respectively
via voltage dividers to pins 125/124 and 127
of the CCU.
In accordance with the Euro/AV standard, pin
8 of the AV socket is defined as 6V (16:9 op-
eration) and 12 V (4:3 operation) AV opera-
tion.
The CCU monitors these voltages on its AV
pins. By division of the respective voltages 6V
= 1.3V and 12V = 2.6V on the pins of the
CCU. If a switching voltage is detected by the
CCU, this switches over to AV operation on
corresponding menu selection.
• IR signals
For the remote operation of VTR devices via
the TV-IR receiver the RSIG signal is applied
to the Euro sockets pin 8.
For this two signal paths are provided. In nor-
mal and standby operation SDA 6000 pin 9 at
H level switches transistor Q 2823, and pin
97, which is also on the signal path, is made
high-resistant from SDA 6000, to avoid inter-
ference. Via Q 2823 and I 2716 the RSIG sig-
nal is passed on to the transistors for socket
selection. Use of the recorder remote control
is necessary for this.
Document Q 2500
There may be applications, however, for
which the video recorder remote control is not
available and the TV remote control emits
another code that the recorder does not un-
derstand. For this a video menu is provided in
chassis Q 2500, which is called up in the re-
mote control with "V=". This allows the basic
functions of the recorder to be used. If for
"Connect video devices" three devices are
selected, they can all be controlled independ-
ently of each other.
In this operating mode the RSIG signal pre-
sent on pin 5 of the CCU is controlled inter-
nally via a code converter and then output via
pin 97 of SDA 6000, which is now low resis-
tant. The other signal path is identical with the
first possibility.
The code converter changes the RC 5 data
words of level 0, as they are delivered to the
IR receiver, to those of level 5, with which the
video recorder operates. Secondly, the code
converter changes the RC 5 command into
the corresponding data word of the NEC code.
Thirdly, the RC 5 commands are converted
into the Korythso code.
The three data words, both RC 5 of level 5, as
well as the NEC code word and the Korythso
code word, are emitted serially by SDA 6000
pin 97. This means that remote control of re-
corders that operate with RC 5, NEC or
Korythso code is possible.
Of course, a recorder must be used that can
process the remote control signal coming from
the AV switching voltage line. For this most
Loewe recorders have a converter.
During output of the converted IR commands
transistor Q 2823 is blocked with L level on
pin 9 of the CCU. This prevents these signals
being affected by IR signals from the receiver
on the operating component.
In order to achieve separate operation of the
three devices connected to the two Euro
sockets, the circuit also contains RSIG signal
switching controlled by the CCU.
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