Regulator For Three Crts - Hughes JVC 100 Service Manual

Regulator for three CRTs

The Regulator PCB is located just behind the Green and Blue CRTs and sits next
to the Green Video Amplifier PCB. The Regulator performs the following
functions:
Regulates the G
!
Voltage (+900V) to each of the three Video Amplifier PCBs
Regulates the G
!
Voltage (-75V) to each of the three Video Amplifier PCBs
Monitors the status of the Video Amplifier PCBs (VA_OK_1,2,3)
!
Monitors the status of the sweeps (/ Sweeps_OK) and shuts down the G
!
and G
2
Regulates the Video Amplifier Supply Voltage (+60V)
!
CRT Protection
The Regulator PCB provides CRT protection, in three ways:
Sweep Failure Protection - If a Vertical Sweep failure is detected by the
!
Vertical Convergence Deflection PCB, the VERT_OK signal goes high.
This signal goes to the Horizontal Deflection PCB. If either the
VERT_OK signal is high or there is a Horizontal Sweep failure, the
/SWEEP_OK signal goes high. This signal goes to the Regulator PCB
where it shuts down the G
Beamcurrent Limiting – If the Contrast or G
!
signal is sent to the Video Processor PCB. The CRT beam current limit is
40µA. If the Contrast adjustment causes a CRT beam current limit the
Video Processor will reduce the Contrast. If this doesn't work, the Video
Processor PCB will reduce the G
Video Amplifier Failure Protection – If the Video Amplifier does not
!
receive its supply voltage REG_VP from the Regulator PCB, it sends a
high / VAMP_OK signal to the Video Processor PCB. The Video
Processor PCB combines the three / VAMP_OK signals from each of the
three Video Amplifier PCBs and sends a / VIDEO_OK signal to the
Regulator PCB. The Regulator PCB takes the / VIDEO_OK signal and
combines this with a check of the incoming G
sends this signal back to the Video Processor PCB as / VA_OK. The
Video Processor PCB combines this signal with the CRT beam current
limiting signal and to shutdown the G
Video Amplifier PCBs. A high input to any of these signals will shutdown
the G
2
2-44
supply from the HVPS and distributes the regulated
2
supply from the HVPS and distributes the regulated
1
circuits if there is a failure
supply voltage.
2
controls to all the Video Amplifier PCBs.
Chapter 2---System Description
is adjusted too high a BEAM
2
shutdown voltage.
2
and G
1 2
control signal going to all the
2
Model 100 Service Manual
1
supply voltages and