JBL 6810, Technical Training Manual

Page: 6 / 43

As seen in Figure 4 the 12Vdc Stand-By voltage
is applied to the 5V Regulator IC500-3 where it
becomes the Keep Alive voltage for Micro-
computer IC1000. The Relay control voltage and
the 24Vdc Start-Up voltage are produced when
the Power button is pressed. The key press is
decoded by the Microcomputer IC1000 into a
logic Low at pin 1, which turns Off Q19 and
turns On Q20. The switching action of Q20 pulls
the Power Relay RY1, Q3 and Q2 to ground. Q1
conducts and applies 24Vdc to the Power Relay.
The relay latches and connects 120Vac to the
Voltage Doubter. Q1 also supplies 24Vdc to the
Horizontal Oscillator Module and Optic Coupler
IC1 on the Power Supply Panel.
A pulse train, developed by the Horizontal
J I 0 3 -
Oscillator Module, drives the Horizontal sweep
circuits and the Switched Regulator on the Power
Supply Panel. R5 and C10 form a two second
timing circuit. C10 begins to charge toward
42Vdc after the Power button is pressed. If the
voltage on C10 reaches 15.8 volts before the
scan derived voltages are developed, zener Z1
turns On. This places Q3 into saturation,
removes Q2 forward bias and shuts down the
Start-Up Supply. During this time period, if
Horizontal Output Transformer T2 and HV
Transformer T4 are driven, the flyback pulses
are rectified and produce the derived voltages. A
scan-derived 24Vdc from the Deflection Panel is
fed through diode D6 to.zener Z1 and turns Off Q1
while in the Run Mode. After the Stand-By and
Start-Up modes are completed, the Run Mode
takes over.
TO
* VOLTAGE
POWER
D 0 U B L E R
RELAY
U
R Y I
_24VDC
CJTP2 TO
. HORIZ
OSCILLATOR
MODULE
DERIVED
24V >
(RUN MODE)
TS10 CONTROLLER
PANEL
Q19
RELAY
CONTROL
SWITCH
Figure 4 - Power On Circuit