Inspection And Troubleshooting; Fault Isolation - Zenith ZVM-1380 Service Manual

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Low capacitance oscilloscope probe - Input
capacitance adjustable from 15 pF to 50 pF, 4
ns rise time. Heath Model PKW-105, or equiva-
lent.
High voltage probe - Zero to 40 kV. Heath
ModeIIM-5215, or equivalent.
Isolation transformer.
Inspection and
Troubleshooting
Use the following procedures to determine possible
external causes of monitor failure.
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Verify proper computer operation and compatibil-
ity.
Check monitor controls for proper response and
settings.
Check the signal and power cables for proper
connection. Inspect these cables for burnt insula-
tion, broken wires, or loose prongs on the plugs.
Check the AC power source for proper operating
voltage.
If the previous inspection did not reveal the cause of
monitor failure, refer to Table 4-1. This table will help
to identify the problem area and suggest the most likely
cause. A board or module will be recommended for
further investigation. The checkout procedure for each
board or module follows after Table 4-1 .
Servicing
Table 4-1
Fault Isolation
PROBLEM POSSIBLE CAUSE ITEM TO CHECK
Dead monitor, No power.
power LED is
not lit.
No raster, High-voltage or
power LED is lit. horizontal circuits.
No display. No video.
No vertical Vertical circuit.
deflection.
Poor vertical Vertical circuit.
linearity.
Poor horizontal Horizontal circuit.
linearity.
Narrow picture. Horizontal circuit.
Poor color.
Video circuit.
Power source.
Power cord.
Power switch.
Power supply.
Fuse.
G2 adjustment.
High-voltage to anode.
Main board
Power supply.
Brightness, contrast,
RGB gain, drive, or
cutoff adjustments.
Video cable.
Main board.
CRT socket board.
Main board.
Deflection yoke.
Vertical linearity or
pincushion adjustment.
Main board.
Horizontal linearity
adjustment.
Main board.
Width adjustment.
Main board
RGB gain, drive or
cutoff adjustments.
Main board.
CRT socket board.
Out of focus. High-voltage circuit. Focus adjustment.
Insufficient
brightness.
Video circuit.
Main board
Brightness, contrast,
RGB gain, drive, cutoff
or G2 adjustments.
Main board.
CRT socket board.
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