Hi Gaker,
This symptom indicated of drop/missing of output voltages in the power supply section. You must check each output voltages in that section feeding the main board and other board to pinpoint where the fault came from and narrow the job.
Once found some abnormal output voltages you may look the following parts for defect.
1. Open fusible resistor.
2. Shorted transistor.
3. shorted diode
4. Leaky/dried capacitor.
You have said that you've already tested the capacitor in the board. But you have to test it not in the board, meaning you have to pull-out it to avoid reading the resistance parallel to its line. If you are using the ohmmeter, upon testing the good capacitor will charged(will have a reading of low resistance and back to high resistance depends upon the capacitance) and discharged gradually.
While bad capacitor will show the following.
1. will have a slow charging and very slow discharging
2. will not charged at all.
3. will charged and gradually discharged and again will charged but this time will not discharged...
Look for 5vdc, 3.3vdc, 15vdc output. That is the common output voltage from the power supply board of LCD TV. Some of the board has a printed output voltages in the board itself, you may check this. If you found missing voltages you may click this LINK if you can't troubleshoot the board.
test the output voltage connected to the load, If you've got the abnormal reading test it disconnected to the board but make sure it will not take more than 30 sec., you may place the test prod of your multimeter to the test point(connectors) prior from powering it on. Ensure safety precaution while you doing this, make sure you will not short the two leads to avoid further damage...
You're reading indicated that the power supply board is not the issue here. This was disable after a start-up check because of the feedback circuitry sense a problem in the load. Re-solder first the bad solder joints and check the parts if already faulty. Most cases I've encountered with the shutdown problem with the related load malfunction was the inverter board.
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What should the output voltages be? If I find low or missing voltage, without having test equiptment other than a digital VOM would it be wise and worthwhile to replace the power board. Do you know the approx. cost of that board?
Thanks
Sorry I havn't gotten back to you. I have not had the time in the last few days to check the voltage as you describe. I hope to do that this weekend. I assume the votlage is no load, with the other boards disconnected from the power supply. Is that correct?
Thank you
Gordy
Before I read your last response, it tested the voltage with the boards disconnected. I noticed when I power up the board I hear what sounds like a relay closing. The voltages are as follows: Vs=196.4, Va=59.5, 5V=5.1,12V=12.1,16.5V=15.95. These readings were consistent for several minutes, until I shut off the power. Then I connected the boards and noticed I no longer hear the click on power up. This time there is no voltage at any of the points. I disconnected the board on the right and the click returned and the voltage was as above. With the video board connected only the voltage is there. With the other board only connected or there is no voltage. I disconnected the small square board on the right and left the large board connected. Still no voltage. On close examination of the right board, I see what looks like three missing components. F5, D3, and D515. I say that because of the way the solder looks, as if there had been a component leaving a circular indentation in the solder ***** at these locations. All the rest of the components and solder appears "normal" to me.
Thanks again.
What usually causes the "load malfunction"? Are you sayng there are NOT missing components in the positions I identified in my last message? "On close examination of the right board, I see what looks like three missing components. F5, D3, and D515" Is the board on the right the "inverter board"? Do you think I should remove the board and look at the solder joints on the back? I think I am about to give up on this TV. Sounds like its getting over my head if it is more than bad solder joints.
All my questions were answered. Thank you.
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