Sharp LC42D43U Loss of video

[ljintexas]

Set comes on and works normally for about 30 seconds..Screen flickers slightly, then loss of video/backlight, audio keeps going. I can turn off and then back on and video/backlight returns for another 20-30 seconds, then goes off again. Power supply had areas that had obviously been hot. Replaced SMPS, really had no effect on symptoms.

[ljintexas]

Re: Sharp LC42D43U Loss of video

I should note, I replaced smps as I actually had one from another set that I knew was good..now i have two that I know are good! I guess my next step is verifying that main board is continuously calling for backlight.

[ljintexas]

Re: Sharp LC42D43U Loss of video

Replaced main board with spare from another set..same result. Could this be an inverter board issue? All fuses on inverter board check good.

[CapLeaker]

Re: Sharp LC42D43U Loss of video

My guess is that the problem is one of the inverter boards. It may be a bad connection, cold solder joint, bad caps, it may be a bad transformer... you'd hafta upload some pics of the inverter boards.

[Drack]

Re: Sharp LC42D43U Loss of video

Yup, sounds like an inverter board trouble

[ljintexas]

Re: Sharp LC42D43U Loss of video

Here is a pic of the master. The slaves are small narrow boards with no harness attached to either one other than the lamp leads..

[CapLeaker]

Re: Sharp LC42D43U Loss of video

Resolder all the blue bypass caps and transformers. Measure with your DMM the resistance of the output winding and compare it to the others (take a paper and make a list). When you compare the transformers, they can't be more than 3% difference in the resistance readings. You have to do that on the Master and on the Slave boards.

[ljintexas]

Re: Sharp LC42D43U Loss of video

Thanks CapLeaker..I will do so and post results.

[ljintexas]

Re: Sharp LC42D43U Loss of video

I replaced the main inverter board and now I do not lose backlight...now I get no reaction to any remote..ordered IR board for $7...scads of them on the internet...means they fail alot. Pictures are fantastic on this set.

Thanks

[CapLeaker]

Re: Sharp LC42D43U Loss of video

Good to hear that you got your set going, albeit now you have a different issue. So what was bad on the original Master inverter anyway? Was one of the transformers secondary off value?

[ljintexas]

Re: Sharp LC42D43U Loss of video

Two of the transformers showed signs of excessive heat on the back side of the board.

[CapLeaker]

Re: Sharp LC42D43U Loss of video

I figured. Very common problem on these LCD's.

[ljintexas]

Re: Sharp LC42D43U Loss of video

Now replaced IR sensor board and have a fully functional set!

Thanks to ALL!

LJ

[CapLeaker]

Re: Sharp LC42D43U Loss of video

thanks for the feedback!