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Trouble shooting for dv3250lcd display

No picture nosound no raster only on screen display working

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Re: trouble shooting for dv3250lcd display

Yes, i agree with the Shuttle83. If you need the free schematic diagram or service manual, please feel free to go to the to get it.

Posted on Jan 20, 2008

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Re: trouble shooting for dv3250lcd display

Hello raj ro,

The problem you have described is a possible problem in the RF/IF section before the video and audio are separated. I would check the tuner, and the signal into the IF/Video/Audio Processor. I say this because in most televisions now the IF, Video, and Audio are preprocessed through the same microprocessor with input from the tuner or some sort of amplifier after the tuner. Check the output of the processor to the various stages Video, Audio, Sync, etc. In addition to this check the DC bias voltages, and the signal waveforms on the processor also. This should lead you down the right path of solving this problem.

You will need:

  • a schematic diagram of the TV (To locate test points and signal)
  • a Digital Multimeter (To measure DC volts and test passive components)
  • an Oscilloscope (To measure waveforms)
  • a signal generator (To provide proper reference signals)
  • an Isolation AC power supply (To prevent shorting out the test equipment while testing the TV set)
These are the basic pieces of test equipment needed to do this type of troubleshooting.

If you do not feel you can do this please contact a qualified TV repair person to troubleshoot this problem.

I hope this helps
Thank you,

Posted on Jan 20, 2008

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Sound on but no pitcher

Sound on means audio section is ok. No picture is video board problem. Pl check input cables. Or give Hdmi cable input. Disconnect all inputs switch on u should get plain raster that is only dots on screen, or blue back screen, if nothing contact authorised dealer,

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It is a common fault to occur in most of the CRT based telvisions, regardless of which brand it is. There will be sound OK, and a bright screen with thin white horizontal lines across; at about an inch space, all over the screen area. This fault may occur along with colur shades also, like blue screen with white retrace line, red screen with white retrace lines, green screen with white retrace lines. Let us take the first case. A white raster with white thin retrace line acorss the screen. These are call vertcial retrace lines technically. To make it mor understand, we have to go to some picture tube electrode details. There are three colour cathodes for a colour picture tube, Red, Blue and Green. Two girds are there called Focus and Screen. Focus grid is supplied with focus voltage which in turn determine the cocus of picture, and screen grid is supplied with screen volrage which determine the emission of the picture tube; in short. There is a final anode to all the picture tubes, which supplied with Extra High Tension voltage, can be located at the top side of the picture tube, to which the EHT voltage from LOT is connected with the help of rubber ****** and clip. Without these three voltages, EHT, Screen and Fcous, no raster will be produced. Therefore in our case, there is a raster, so, horizontal output section including Line Output Transformer [LOT] is functioning well, and as far as sound is there, tuner and video IF section are working well. In fact, all other section except, video output section is working properly.
There are three cathode points on the base card, marked as Bk, Rk and Gk. Check the voltages of these three cathodes. In our case, it will be very low or approximately equal to zero. When cathode voltages goes low, emission of the CRT increases, is the reason. There must be a voltage between 120 and 135VDC at these points. Find out the reason for this voltage drop is the next step. The video drive voltages in most TVs comes from LOT windings, after rectification and filtering. There will be one reisitor of low value, say one Ohms or so, will be connected series with this winding, in between diode and winding. Check the voltage at the cathode of this rectifier diode first. If found low replace the diode and the smoothin capcitor. The smoothing capacitor will be between 33 and 47MFD 250VDC rating. Replace both of them. If there is volatge, say 200VDC or so, check whether this voltage comes to the CRT base board or not, If not, check the conducting wire, serial resistors; if used for open. There is no chance of transistor shortage at this time as the raster we see is white. If raser we see have a specific colour predominent, that is green, blue or red, check the revalent video out transistors and replace it. It is best to replace all the three video output transisors at the same time with same batch and number.

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