Technology of Q 2500 colour TV set

Technology of Q 2500 colour TV setAs both the vertical and the RGB output stageobtain their operating voltage from the diodesplit transformer, this allows the entire c.r.t. tobe switched off and the power input in thismode to be reduced. In normal operation pin79 of the CCU is at L level and transistor Q2951 is high resistance.The c.r.t. is switched off when:a) a timed recording for a video recorder isbeing processed in the TV set.b) on switch off using the remote control, ifpreviously, via the video menu, a recorderhas been set to record.c) on switch off using the remote control, ifpreviously overplaying between the socketsof the TV has been activated.d) Radio – operation is activated (after 20sec.).In all these cases all other stages of the chassisare fully operational. Except for d) thesound in the MSP 3410 is switched off via theI²C bus.4.1.12 SAT unit controlControl of the Sat/TwinSat unit is implementedby the CCU via the I²C-Bus 2.The SAT unit VI used is also able to controlappropriately equipped switch boxes or LNCsvia DiSEqC Level 1 (Digital Satellite EquipmentControl). In this system pulse modulationof the 22 kHz signals allows data to be exchangedbetween receiver and peripheral devices.This means that the current differentLNC supply voltage switching information, 22kHz and control function will be replaced andsimplified by separate control lines.In the standard, a logical 1 is defined as 11periods of 22 kHz signals (0.5 ms) followed bya 1 ms pause (22 periods). The logical 0 isrepresented in reverse, i.e. 22 oscillations (1ms) and then a 0.5 ms pause (11 oscillations).For this, each bit requires 1.5 ms for the transfer,which corresponds to a maximum transferspeed of 666 bits per second. After eachtransferred telegram, there must be a pauseof at least 6 ms (132 periods).Control is implemented according to the SingleMaster - Single/Multi Slave principle. Masteris always the SAT receiver, and the externalcomponents (LNC multiswitch, etc.) arethe slaves. Therefore, each communicationfrom the receiver is started and the externalcomponents can only transfer data, after theyhave been requested to do so by the master.A command from the master contains a 1 byteframe, a 1 byte address, a 1 byte commandand 1 or more bytes of data. The responsesconsist of a 1 byte frame and 1 or more bytesof data. Each byte is always followed by aparity bit (P) for error checking.The frame byte determines, whether the datais sent by the master or the slave. The addressbyte contains the information that determineswhich peripheral module (switchbox,LNC ....) is addressed. The command bytedetermines which switching function is to beimplemented (selection LNC, level switching....). In the data byte additional information canbe exchanged. There is still enough freespace in the DiSEqC command set for futurerequirements. This means that the system hasbuilt in futurability.For the DiSEqC control the SDA 6000 has aninput and output respectively. Communicationwith the SAT unit in the device is via a commonline on connector W 1211, pin 7 on thebasic board and from there via W 250, pin 8on the SAT unit.Pin 90 of the CCU is used as an output for thecontrol of peripheral devices. The 22 kHzsignalon the SAT unit is switched using theH level. By switching between the L andH level the 22 kHz is switched by the SAT unitfor the required period and a command is thenissued via the coaxial cable.Document Q 2500 71 © Loewe ProCollege