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.
An expert who has achieved level 3 by getting 1000 points
An expert that got 10 achievements.
An expert that got 5 achievements.
An expert who has answered 1,000 questions.
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.
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
The fault is a failure of the deflection circuit and since you have not specified whether it is a vertical or an horizontal line the section failed will be related to the position of the line.
If horzontal the vertical IC or the section related is faulty and if Vertical the horizontal section., Now this can be the deflection IC, teh deflection coils or even discrete components like capacitors or resisitors in this section which will require a signal trace with a voltage test before the absence of the sync pulses are confirmed and the section identified.
I request not to change the IC unless it is proved but you can solder the vertical IC or the section concerned -- if there is dry soldering.
There is a failure in the vertical deflection circuit. Typically there is a vertical output i.c. that provides the deflection vertically. The i.c. itself is a fairly common component to fail. There are some lower power circuits that feed this output device that also could be the problem. When the electron beam in the tube is not deflected vertically it "writes" only horizontally across the center of the screen thus resulting in a single trace. Be careful not to leave this at high brightness for any extended time as it can "burn in" that area of the screen. Unless you are a "techi" this is a job for a qualified technician. Troubleshooting would be in the vertical deflection section of the set. Most of the parts are not expensive in themselves, except for the deflection yoke which sits around the neck of the tube. The cost to repair would typically be the shop labor.
The problem sounds like a vertical deflection issue form what you describe. On average they are usually in the simple repair categories. On average they would run in the $50 range if you take it to a reputable repair shop. There are several possibilities Bad capacitor (s) Bad vertical IC resistor in the power supply to the vertical circuit changing value
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..
This problem is generally due to aged Electrolytic capacitors in the Vertical section.
Again, to save time, I invariably replace all the 8-10 El caps in this stage at one go. solves the problem, saves time, and also protects the customer from bringing in the machine again in another 2-3 months, for another bad capacitor problem.
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.