Kenwood CS-1575D Service Manual

CS-1575D7CIRCUIT DESCRIPTIONDisplay Switch CircuitIC206(1/4 and 2/4) is a transmitter for displaying chops.IC207(1/2 and 2/2) is a vertical and horizontal mode controlcircuit.Sweep CircuitTrigger gate signals drive Q217 to control the hybrid IC201.The IC201 contains a constant current, charged type rampwave generating circuit whose time constant is determinedusing the S201 code and C219 or C220. If the value of theS201 code is not greater than 1ms/Div, Q216 is turned ON,C219 is selected, and the time constant adjusting circuit forQ215 is activated so that VR201 adjusts the time constant.Ramp waves produced here are input into the upper limit cir-cuit consisting of Q220, IC205(1/4 and 2/4), D219, D222,C228 and C229, and the hold-off circuit via the buffer ampli-fier of the emitter follower Q218, and then generate sweepstop signals and hold-off end signals. Ramp waves are inputalso into the horizontal output amplifier via the sweep circuitand X-signal switch circuit. VR202 is a regulator for control-ling the gain of ramp waves.Horizontal output CircuitBy giving Q301 horizontal signals and giving Q302 voltagesignals representing the horizontal position, the collectorsQ307/309 and Q308/310 are given differential signals fordriving the X deflecting plate of the CRT. Q303 throughQ310 are a constant current load type feedback amplifierwith good linearity and low power consumption. VR302 is aregulator for operating point voltage.Power System (x80-1420-00)The power system consists of a low voltage circuit, high volt-age circuit and blanking circuit.Low Voltage CircuitIC401 is an HIC for controlling four systems of Å}8V, +140Vand +5V. The voltage for each system comprising control-purpose transistors Q401 through Q405 is determinedbased on the -8V system. VR401 is a regulator for the -8Vsystem. The rectifier diode D401 for the +140V system givesswitching signals for CAL signals.The +10V circuits D406 and C410 are unstable, and consti-tute a power source for the horizontal sweep HIC(IC201).High Voltage Blanking CircuitQ408 oscillates at approximately 60 kHz making use of thereactance of the converter transformer T401. The oscillationvoltage appearing in the high voltage coil is kept stable at -1800V thanks to the voltage doubler rectifier circuits C425,C426, D409 and D410, and the control circuits Q409 andIC402. T401 contains a CRT heater coil which is turned onvia R452.Voltage signals of approximately 300Vpp are taken from thehigh voltage coil, and used as modulated signals for blank-ing. This is necessary for employing signals from blankingamplifiers Q406, 407 and 415 for the cathode potential. Themodulated signals drive the DC regeneration circuits D411-414, C423 and C424, and provides signals for controllingthe brightness of the CRT G1 electrode.Q410, 411 and 412 are a transistor for focus control.Q416 gives the CRT G2 electrode the required voltage.Q413 and Q414 drive the trace rotation coil. VR402 is abrightness regulator. VR403 is a focus regulator.Other Circuits(x80-1420-00 H/8)Q501 is turned on/off by CAL signals from the power source.Q501 provides the calibration voltage (100 or 120 Hz).VR507 is an ASTIG regulator. VR508 is a trace rotation reg-ulator. VR509 is a focus regulator. VR510 is a brightnessregulator.Panel Circuit(x80-1420-00 c/8)S501 is a trigger source changeover switch. S502 is a dis-play mode changeover switch. S503 is a phase displayON/OFF switch.VR501 provides adjustment of SWEEP variables. VR503and VR502 provide adjustment of the vertical position ofCH1 and CH2 respectively. VR504 provides adjustment ofthe horizontal position. VR505 provides adjustment of thehorizontal position of CH2 in the DUAL-H display mode.VR506 provides adjustment of trigger level.