Technology of Q 2500 colour TV set

Technology of Q 2500 colour TV setAfter switching to the service mode, chassistuning is implemented with the FB transmitter.The service mode is called up by pressing thefunctional button “?“ four times, so that the“Service“ display appears, and then pressingthe “M“ button on the remote control withinone second. Then using the curser buttons,the individual tuning functions can be calledup. Tuning is also carried out using the cursorkeys. The data is initially stored in the workingmemory C 161 and is only transferred to thememory on operation of the "ok" memory button.Once returned to normal FS operation,use the "E" button to return to remote operation.Pressing the Z 1 button switches the remotecontrol processor to another mode. Thismeans that the transmitter can be used forboth a videorecorder and DVD player fromLoewe. For the videorecorder, however, controlis only possible with Korythso code, asused by Panasonic. For the DVD player weuse the RC 6 code.If the remote control is not used in the videorecorderor DVD mode for 20 sec, then itautomatically switches back to the TV mode.The video or DVD mode is displayed for Control10 by the LCD and for Control 150 by anLED on pin 2 (Y1) and pin 3 (Y0).For Control 10 the LCD is controlled fromports Y3 to Y7. Up to Y3 these are also usedto query the button matrix.The operating voltage is also monitored inControl 10 and displayed correspondingly inthe LCD. Measurement of the battery voltageis carried out by transistors Q 416, Q 414 andQ 404 on pin 5 of 84 C 122.4.1.2 Infrared receiverC8216I 8216InfraredrecieverR8216R8205R8217Q8202U5SBRC55V0VThe IR receiver on the local control unit is athick film circuit and is fully encapsulated.The IR signal from the transmitter is convertedinto an electrical signal by the receiving diode,amplified and prepared in such a way that it isavailable on the output as 2 Vss.With the next transistor Q 8202 on the localcontrol unit the signal is amplified to 5 Vss. Inthis way the IR decoder in SDA 6000 can besafely controlled via pin 5Via IC I 2716 and transistors Q 2721, Q 2731and Q 2741 the IR signal is applied to pin 8 oneach of the three Euro sockets. This allowshidden videorecorders to be remotely controlledvia the IR receiver of the television setand the AV switching voltage line (see AVoperation).Via Q 2823 the signal reaches transistor Q2862 on pin connector W 1076. Via W 1076the IR signal is supplied to a connectedonline-box.The pulse width for the RC 5 code of the remotecontrol is about. 900 µs. If a connectedMulti Media Component is operated with theControl@media IR keyboard, the data is nottransferred with the slow RC 5 code, but withan RC MM code (MM-Multi Media) designedfor fast data transfer. The pulse width for theRC MM code is 167 µs.The pulse width of 167 µs requires an IRreceiverwith a very short time constant.Therefore, in Multi Media devices a special IRreceiver is used, which for operational pur-Document Q 2500 65 © Loewe ProCollege