Sanyo C25ZG45 Service Manual

Also see for C25ZG45: Instruction manual

Circuit Description4. AUDIO OUTPUT4-1 (AN5265)-Monaural modelThe audio signal output from pin 50 of IC101 is inputted topin 2 of IC171 and passes through the pre - amplifiercircuit and the drive circuit into the audio amplifier. Theaudio amplifier is the SEPP (Single - Ended Push Pull)type and the output from pin 8 drives the speaker directly.4-2 (TDA7263M)-Stereo modelThe audio signals output from pins 17 and 18 ofICI 101 (MC44131 PB) are inputted to pins 1(Left) andl 5( Right) of IC1 102 and passes through the pre - amplifiercircuit and drive circuit, after which it is input to the audioamplifier. The audio amplifier is the SEPP (single- ended,push - pull) OTL type and the outputs from pins 8( Right)and 10( Left) drive the speakers directly.5. VERTICAL OUTPUTL An LA7833 is used for the vertical output circuit in thischassis. The vertical ramp signal from pin 43 of IC101 isinputted to pin 4 of IC451. This ramp drives IC451, andvertical scanning is performed. In the first half of scanninga deflecting current is outputted from pin 2 and passesthrough the following path:VCC(B4) + D451 + pin 3 + pin 2 + DY + C461 +vR451/R459.An electric charge is then stored in C461. In the last half ofscanning the current path is:C461 + DY + pin 2 + pin 1 +VR451/R459 + C461In this way, an increasing sawtooth waveform currentflows directly to the DY to perform electron beamdeflection. During the first half of the blanking period thevertical ramp signal suddenly turns OFF. Since there is nolonger any current flowing into the DY, the magnetic fieldcollapses causing an induced current to flow as follows:DY+ pin 2+ pin 1 +VR451/R459+C461 + DYL Once the magnetic field in DY has dissipated, the currentpath becomes:Vcc+ pin 6+pin 7+ C452+pin 3@pin 2+ DY+ C461+ VR451 /R459and when the prescribed current value is reached, thevertical drive ramp signal turns ON.This completes one cycle.6. HORIZONTAL OUTPUTThe horizontal oscillation signal is outputted from pin 37 ofIC101 and used to switch the drive transistor Q431. Thisswitching signal is current amplified by the drivetransformer T431 and drives the output transistor Q432.When Q432 turns ON, an increasing current flows directlyto the DY throughC441 /C442 + L441 /R441 + DY + Q432- C + Q432- Eand the deflection occurs during the last half of theL scanning period. When Q432 turns OFF, the magneticfield stored in the DY up to that point causes a resonantcurrent to flow into the capacitors C420 and C423 andcharges them.The current stored in C420 and C423 then flows back tothe DY causing an opposite magnetic field to be stored inthe DY. This field then collapses increasing a currentwhich switches the dumper diode in Q432 ON. Theresonance state is completed, and an increasing currentthen flows again directly to the DY through the dumperdiode.By this means, the deflection in the first half of thescanning period is performed. When Q432 turns ON at theend of the first half of the scanning period, the deflectionduring the last half is begun, thus completing one cycle.In the PCC circuit consisting of Q461 and Q462, theparabola signal supplied from the vertical circuit is addedat the horizontal output stage and pincushioncompensation is performed by varying the DC bias.Further, the ABL voltage is fedback to the base of Q462 tocompensate for width variations due to variations in thebeam current.–5–