64
27. Grand Wega Lamp Control
Defect – No backlight repair flow chart:
The following flow chart will help you quickly ID the problem board, but you must be careful. High Voltage at a
very High Current is present (not like a TV’s FBT where there is low current).
Be aware that if the backlight does not start at power ON, the lamp HV circuitry is repeatedly instructed to try to
turn ON for two seconds and again five seconds later until the TV shuts down. Therefore you must keep away
from the HV when the TV is plugged into AC. To use this flow chart, you will need a DVM to determine which
board is defective.
4/16/02
Symptom = Fan ON
but Backlight OFF.
Standby LED blinks,
A/V muted. TV shuts
down after 3 minutes.
With the TV
unplugged, bend down
the left C101 capacitor
on the Power Block as
shown to make
cylinder G1 visible,
Watch the G1 spark gap behind
C101. Turn ON the TV. Do you
hear a HV frying noise or see light
from the G1 body?
WARNING
- At TV turn ON, LETHAL
HV at high current (unliked an FBT)
outputs the Power Block. Observe
spark gap cylinder G1 for HV from two
feet away or more. Close front panel
lamp door so HV can start
Does Ctl (white
wire) change to
5Vdc * at TV turn
ON?
Is there 255-350
Vdc Across the
Power Block +/-
connector?
Remove 2 screws and
unplug the lamp socket.
Lay the HV connector
down away from metal or
people. Turn ON the TV.
Is there arcing at G1?
The circuitry is working.
Unplug the TV.
Inspect the HV socket for
corrosion (white powder).
Replace the UL200 Lamp.
* This Ctl voltage will only
be present for 2 seconds
and then again for 2 more
seconds 5 seconds later.
Replace M
board. Does
Lamp light?
Finished
No
Yes
No
Yes
No
Yes
Yes
Replace Power
Supply G board
Replace the
Power Block
No
Gnd
prt
Ctl
+/-
Connector
Power Block - Side View
G1
C102
C100
C101
G1
Corner - top view
FIGURE 27-5 - DEFLECT - BACKLIGHT DOES NOT LIGHT
