Sharpe LCD TV LC60E77UN

[BruceGilbert]

Re: Sharpe LCD TV LC60E77UN

Thank you for getting back to me. If you look at the above pictures the second one of the back of the board you will see the opto isolators at the top The bottom one is IC7900 and the resistance between pin 3 and 4 is 3.41 meg ohms however the IC above this one IC7906 the resistance between pins 3 and 4 is 2.8 ohms and there is a Zener diode D7905 that has a resistance of 2.8 ohms either way I test it. This diode is connected between pin 4 of IC7900 and pin 4 of IC7903. Hope this helps.

[dick_barton]

Re: Sharpe LCD TV LC60E77UN

If you disconnect the zener check if that is what is short circuit and also check the resistance across the empty pads. Also what the reistance is now between Pins 3 & 4 of IC7906

[budm]

Re: Sharpe LCD TV LC60E77UN

if you disconnect the zener check if that is what is short circuit and also check the resistance across the empty pads. Also what the reistance is now between pins 3 & 4 of ic7906

+1

[BruceGilbert]

Re: Sharpe LCD TV LC60E77UN

For you information I removed D7905 and measured 2.4 Ohms either way. I measured 117 Meg ohms one way and 3.41 Meg ohms the other way. I am sorry I am going by memory for the exact values. I did not measure between pins 3 and 4 of IC7906 but I will today. I believe that the Zener diode D7905 needs to be replaced Correct? It will take a few days but I will replace it and report the out come. Thank you everyone. budm I am not sure what you were asking by typing +1 are you looking for some additional information? Thank you

[nomoresonys]

Re: Sharpe LCD TV LC60E77UN

+1 means that he agrees with Dick Barton's suggestion.

[BruceGilbert]

Re: Sharpe LCD TV LC60E77UN

I have measured between the resistance between pins 3 and 4 of IC7906 and it reads 17 meg ohms. Now to order a replacement Zener diode. I spoke to my local Jentronics dealer and he seems confident that he will be able to identify a replacement diode.

[BruceGilbert]

Re: Sharpe LCD TV LC60E77UN

Update I have ordered the Zener diode D7905 and will install it once it arrives and update my findings. Is the above readings inline with what is expected? IC7906 between pins 3 and 4 17 meg ohms.

[dick_barton]

Re: Sharpe LCD TV LC60E77UN

Again without the schematic to go on it's difficult to say what is correct or not, however 17 megohms across pins 3 & 4 (the internal transistor of the opto not powered up) is at least not a short circuit.

[BruceGilbert]

Re: Sharpe LCD TV LC60E77UN

Here is the latest update. I finally received the Zener Diodes that I suspected had failed and I replaced D7905. I then powered the TV up and it came to life. That was the good news. Attached is what is now displayed on the screen. I believe that I still have a power problem but also a video fault. I feel now that this is beyond my capability so I am going to throw in the towel unless the fault is obvious to anyone. Thank you very much to everyone who helped me along the way.