- 5 -
Service Notes (Continued)
IMPORTANT
: To protect against possible damage to
the solid state devices due to arcing or static discharge,
make certain that all ground wires and CTR DAG wire
are securely connected.
CAUTION
:
The power supply circuit is above earth ground and the
chassis cannot be polarized. Use an isolation
transformer when servicing the Receiver to avoid
damage to the test equipment or to the chassis.
Connect the test equipment to the proper ground
(Hot ) or (Cold
) when servicing, or incorrect
voltages will be measured.
WARNING
:
This Receiver has been designed to meet or exceed
applicable safety and X-ray radiation protection as
specified by government agencies and independent
testing laboratories.
To maintain original product safety design standards
relative to X-ray radiation and shock and fire hazard,
parts indicated with the symbol
on the schematic
must be replaced with identical parts. Order parts from
the manufacturer’s parts center using the parts
numbers shown in this service manual, or provide the
chassis number and the part reference number.
For optimum performance and reliability, all other parts
should be replaced with components of
identical specification.
X-RAY PROTECTION CIRCUIT TEST
Preparation
1.
Connect a High voltage meter (Capable of handle
50kV) to the CRT anode
2.
Connect a variable resistor (3K) in series with a
100 ohms resistor, across (in parallel) R849.
3.
Connect a jumper in R850 position (make a short
on R850).
Procedure:
1.
Plug receiver to120V ac. and turn it on.
2.
Apply a monoscope pattern.
3.
Set PICTURE and BRIGHTNESS to normal.
4.
Set variable resistor to maximum level (3k)
5.
Slowly decrease variable resistor value.
6.
Adjust beam current between 50
µ
A and 100
µ
A
with the SCREEN VR of FBT.
7.
Adjusting the Variable REsistor, check if the set
starts to loose synchrony
8.
Confirm the reading from the High Voltage meter
is 38KV for 25” models and 34KV for 20”
models.
9.
Turn Off the receiver and remove the jumper.
