Sony D98 chassis Operation Manual page 4

Pin 2 – OCP - Over current protection. Used to determine the overload level at which the timer latch is activated.
Pin 3 – CF – Oscillator. With a capacitor, determines the switching frequencies. (On/Off times.)
Pin 4 - CLM - Over current protection. If the voltage on this pin (primary current feedback) exceeds -0.18V, the power
supply will enter cycle-by-cycle current limit mode.
Pin 5 – GND- IC ground terminal.
Pin 6 – OUT- Output driver for switching transistor Q602.
Pin 7- VCC- IC supply voltage terminal. This voltage is nominally 17.5 volts during active on mode and 12 volts during
suspend or active off mode. The IC receives starting current via startup resistor (R613) until the auxiliary supply is available
from T601 VCC winding. If the voltage on this pin exceeds 19.4 volts (OVP), the power supply shuts off and can only be
restarted by disconnecting and reconnecting the AC line. Under voltage lock out (ULVO) occurs when the voltage is less than
9.5 volts.
Pin 8 – SD- Used for OVP and timer latch functions. A capacitor determines the timing for OVP function.
Pin 9 - FB – Feedback terminal.
Operation
The power supply is a flyback type converter. It has both PWM and RCC characteristics. The PWM controls the pulse width
of the gate drive. The RCC portion insures that the next conduction cycle starts at zero volts. Therefore, the gate pulse width
varies and the switching frequency also varies. The on and off timing is determined by pins 3 and 1. Pin 1 detects the zero
voltage point or the valley on the relaxation ringing waveform.
When AC is applied to the power supply, start up current is supplied though R613 to pin 7 of IC601. Startup voltage is
approximately 15V. After start up, the voltage to pin 7 of IC601 is supplied through D605 connected to T601 pin 8. The first
mode of operation is active off mode and the VCC will be approximately 12 volts. The output drive pulse frequency will be
near 40kHz. or a type of frequency burst mode.
When the power supply enters active on mode, the switching frequency will vary between 65 and 120kHz., depending upon
input voltage and power level. The VCC level will be approximately 17.5 volts. OVP threshold is 19.4 volts and UVLO is 9.5
volts. Therefore, if the VCC voltage is not correct, the power supply will not operate properly.
Feedback from the secondary side comes through IC603 and is connected to IC601 pin 9. (See diagram on page 5.)
3. Secondary Circuitry Section
The secondary section consists of the following circuits. Rectifier diodes and filters for all output voltages, horizontal
centering, +5/12 volt regulator, +5 volt back up circuit, heater voltage regulator, voltage feed back circuit, standby mode
feedback, B+ detection and protection circuits. This section will describe each circuit and its function.
Secondary Rectifiers
The secondary rectifiers supply the following voltages, 180V (B+) deflection and video, 80V video, ±16V deflection and
regulators and 8 volt heater regulator.
Horizontal Centering
This circuit supplies IC502, which is used to adjust horizontal raster position on the CRT. The horizontal centering circuit
consists of fusible resistors R621 and R622, diodes D648 and D649 and filter capacitors C656 and C657. In respect to the
secondary ground, the horizontal centering ground is floating and connected to –H DY line. The voltages in reference to this
floating ground are ±8 volts. Care should be taken to not short the floating ground to the secondary ground.
+5/12 Volt Regulator
IC605 is the voltage regulator for +5 and +12 volt lines. The output voltages are supplied to the microprocessor, deflection
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