Sony TVP-08, Training Manual

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25
Regulation
Overview
The regulation circuit is used to provide a control voltage that determines
the oscillating frequency of the IC6003 Oscillator. This is done by using
the +11 volt line for this circuit’s supply and the +135 volt line as the input.
Operation
The +11 volt line is applied to IC6005/1 and then goes through the internal
LED connected between pins 1 and 2 of IC6005. The voltage at IC6005
is applied through R6128 to IC1601/2. IC1601 VCC Controller varies the
resistance between IC1601/2 and ground. When the voltage on the +135
volt line goes down, the resistance between IC1601/2 and ground also
goes down. This causes the current through the internal LED of IC6005
to increase, thereby increasing the brightness of its light. The increase in
the brightness of the internal LED causes more current to flow between
the C-E junction of the internal transistor inside IC6005. When this tran-
sistor conducts harder, it causes more current to flow through D6023 and
D6024. This in turn lowers the voltages at IC6003/2 and 6. When these
voltages are lowered, the frequency output of IC6003 Oscillator is low-
ered. The oscillator output is at IC6003/9 and 10. When the frequency
output is lowered, it becomes closer to the resonant frequency of the
power supply, increasing the voltage on the +135 volt line.
If the voltage on the +135 volt line should rise, the resistance at IC1601/2
and ground will also rise. This causes the current through the internal
LED of IC6005 to decrease, which decreases the brightness of the light.
The decrease in the brightness causes less current to flow through the C-
E junction of the internal transistor inside IC6005. When less current
flows through the C-E junction of this transistor, it causes the voltages of
IC6003/2 and 6 to rise. This in turn causes the frequency output at IC6003/
9 and 10 to increase. This will lower the voltage on the +135 volt line.