No vertical deflection,only a thin horizontal line.
I would appreciate any help I can get for the following problem: My television set is a Panasonic CTN 2766S and chassis APEDP204.
Problem: The top of the picture was a couple of inches short when the tv was first turned on. After five minutes or so, the picture filled out to normal and stayed that way.
It did this for about a year and then when the set was turned on, it only had a horizontal line in about the middle of the screen. It did not fill out no matter how long it was on.
I replaced the IC 451(LA7836-TV) “VERT OUT” and, also, replaced C553, 22UF/250V with a 32UF/250V capacitor because a service bulletin said the capacitor was drying out. That caused an increase in beam current resulting in a broken CRT neck.
When the tv was turned on. The raster filled out except for the top couple of inches. Adjusting the vertical size pot did not have any effect. IC 451 was getting hot in a short time. After 30 minutes the raster did not fill out, like it had done previously. I heard a sound like something was shorting out and the raster disappeared leaving only a horizontal line on the screen.
I made a check of IC 451 and found it was shorted.
Again, I would appreciate any help with this problem.
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Re: No vertical deflection,only a thin horizontal line.
I suspect you have some background in electronics so I'll ask you some questions.
First, I know that you changed the output ic and a capacitor, the capacitor caused excessive beam current, that's bad, remember that beam current is dangerous because it can produce X-Rays. Remember to use the exact value of parts for X-Ray generating areas of the TV. So replace the C555 with the rated value by the manufacture.
As far as the vertical deflection problem it sounds like you may have a shorted vertical deflection coil (part of the yoke transformer). I would suggest testing the coil to see if it is shorted (A ring test will determine this). The Sencore LC102 has a ring test feature or you can lookup how to build a simple ring tester. In any event replace the IC and test the yoke transformer for shorts on the vertical winding.
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Dec 30, 2013 - Uploaded by Pet Rock's Garage
This video covers how to fix a Panasonic 42" Plasma TV model TH-42PX600U that has vertical distorted ...
this is a indiciation of loss of vertical deflection. is the a thin horizontal line? I have found feferences that capacitor c517 in the horizontal cuircit was shorted cause this .. cant be sure... also other components that might be at fault is the vertical ic 1509 transitor q1505 vertical buffer.
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 screen/G2 pots.
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. Hope it works well...
replace the vertical Ic and it probably failed because of the two Electrolytic Capacitors so check and replace if necessary. Not for a beginner but if you are good with a soldering iron and ****** it is possible.
This symptom is characterized by a thin horizontal line in the middle of the screen. This symptom is caused by the absence of the deflection sawtooth current in the horizontal deflection coil.
The trouble is easily isolated by a continuity test and by checking the most likely defective components such as A)open vertical linearity compensation transformer, B) open capacitor and C) open horizontal deflection coil.
Be sure to decrease the brightness first before trouble-shooting if the line is very bright,as it burn the phosphor screen..
If you indeed have a line down the center of the screen that means the horizontal output transistor is working as it produces high voltage as well. The rectifiers are working otherwise you would have no power or sound. What you need to look at is either the horizontal windings of the deflection yoke are open or you have a open return from the yoke to the horitontal output stage.