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SECTION 4
SAFETY RELATED CHECK
4-1. CIRCUIT CHECK FOR SAFETY
1) Input the color bar signal.
2) Connect a 1/2W, 470KQ resistor between Q1814-B of D
board and GND (J90).
3) As soon as connecting the external resistor, the receiver
stops operating (power:relay off). And removing the
external resistor, the receiver operates normally when
plug in the AC POWER CORD after plugging it out.
4-3. HOLD-DOWN CHECK
4-2. VERTICAL SHORT CIRCUIT CHECK
1) Input the color bar signal.
2) Short both terminals C1311 from outside.
3) As soon as shorting C1311, the receiver stops operating.
And removing the external short, the receiver operates
normally.
This procedure should always be performed when replacing the following components (marked with
.@ on the Schematic
Diagram).
; 1C1501, ZD1402, T1402, DY
1) Circuit Diagram
R1426
XX
W——o
D1403
4
FR1417
R1428
R1427
Y
ZD1402
D1402
2) Circuit operating explanation.
@
Normal condition
DC voltage appears at point X from FBT pulse by
rectifying circuit consisted of FR1417, D1403, and C1428.
DC voltage of point Y is divided into R1428, R1427,
R1418 from DC voltage of point A.
in normal condition, DC voltage of point Y is lower than 6
volt.
So the set is operated normally.
e@ Abnormal Condition
In abnormal condition, DC voltage of point X increase in
proportion up to ? volt.
Therefore, the hold down circuit is operated.
In result, the horizontal frequency is stopped.
3) Check the X-Ray protection circuit.
a. Turn on the set and connect the color bar signal at the
antenna terminal.
b. Check the B+ voltage whether it is correct or not.
c.
If B+ is incorrect, power circuit is to be repaired.
d. To check the operation of hold down circuit, short
points X and Y.
e.
Identify the screen status whether raster is appeared
or not.
f.
If there is distorted synchronism of screen, the set is
OK.
g.
Remove the shorted jumper from points X and Y.
4) Troubleshooting the Hold-Down circuit.
Shorting points Xand Y_ check the voltage of point Y.
e
If the voltage is below 6V DC, check ZD1404, C1428,
L1406, R1419, FR1417, and D1403 and replace defective
one.
@
if the voltage is over 6V DC, C1405, R1405, 101501 and
replace defective one.
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39
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KV-20/13VM30/31
RM-Y138/W
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