CAUTION: To prevent damage to the CRT phosphors, immediately turn down the
brightness so the line is just barely visible. If the user controls do not
have enough range, you will have to locate and adjust the master brightness or
|NotTaR of Television Sets : Single Horizontal Line
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A single horizontal line means that you have lost vertical deflection.
High voltage is most likely fine since there is something on the screen.
This could be due to:
- Dirty service switch contacts. There is often a small switch located
inside on the main board or perhaps accessible from the back. This
is used during setup to set the color background levels. (On some sets,
this is located on the CRT neck board and may be a jumper plug or other
means of selecting service mode - not an actual switch.)
When moved to the 'service' position, it kills vertical deflection and video
to the CRT. If the switch somehow changed position or got dirty or corroded
contacts, you will have this symptom. Flip the switch back and forth
a couple of times. If there is some change, then replace, clean, resolder,
or even bypass it as appropriate.
- Bad connection to deflection yoke or other parts in vertical output
circuit. Bad connections are common in TVs and monitors. Check
around the pins of large components like transformers, power transistors
and resistors, or connectors for hairline cracks in the solder. Reseat
internal connectors. Check particularly around the connector to the
deflection yoke on the CRT.
- Bad vertical deflection IC or transistor. You will probably need
the service manual for this and the following. However, if the
vertical deflection is done with an IC, the ECG Semiconductor
Master Substitution guide may have its pinout which may be enough to
test it with a scope.
- Other bad parts in vertical deflection circuit though there are not
that many parts that would kill the deflection entirely.
- Loss of power to vertical deflection circuits. Check for blown
fusable resistors/fuses and bad connections.
- Loss of vertical oscillator or vertical drive signals.
The most likely possibilities are in the deflection output stage or
bad connections to the yoke.
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