Hello, folks. I've done more than a few TVs and monitors in the past but this time around I am utterly puzzled. Perhaps somebody would chime in. I also searched the forum extensively and read all the relevant threads but couldn't find the answer.
The patient is Olevia 265TFHD-T11. The blue power LED turns on when the TV is plugged into the AC outlet and turns off when the power button is pressed. The TV turns on fine, but the screen is completely dark. No logo. No 2 seconds to black. No faint picture on the screen under bright light. Nothing at all. I don't know its history and have no clue as to which symptoms if any had preceded its failure.
No swollen capacitors anywhere. The Main PCB lights up like a Christmas tree and shows all the voltages listed for a good motherboard in this picture (Moderators: please let me know if I have stepped over the line by posting a link to a picture in another forum). Both PSUs are good as well, although one thing remains a mystery - more about this later.
Since IME the flashlight test does not always produce reliable results, I first looked at the inverters/tubes. There are 36 of them (6 boards x 6 inverters). Not one had lit up my trusty home made diagnostic probe built around a neon bulb from an old power switch, a 120k ballast resistor, an empty Bic disposable pen, two #120 Singer sewing machine needles, two old Fluke test probes with wires and some heat shrink tubing. I don't believe in coincidences, much less in 36 of them in a row, so naturally I shifted the diagnostic efforts upstream.
The 6 inverter PCBs are arranged in the following manner: 3 PCBs on each side, where 1 central PCB is bridged to 1 above and 1 below.
In addition the left and the right central PCBs are bridged to each other with a harness comprised of 24 thin gauge all-white wires.
In addition the left central inverter PCB (let's call it the Master Inverter PCB) also has a mystery 4-pin connector populated by identical thin gauge white wires. This small harness is connected to the T-Con PCB. No silkscreen labels on either side of this harness.
All 6 inverter PCBs receive stable 24v (23.7v to be exact) via 10-pin harnesses (5 BLK and 5 RED wires in each) from the PSUs.
There is no voltage ever present on either of the 24 pins of the all-white harness in either OFF or ON state.
There is no voltage ever present on either of the 4 pins of the all-white mystery harness in either OFF or ON state.
After turning ON one of the green LEDs (D202) on the Main PCB lights up with a 2 second delay relative to the other LEDs on this board and as soon as it does +4.2v (Pin PSON on the PSU) appear on the Brown wire between the Main PCB and the PSU. However this +4.2v signal (or any voltage other than +23.7v for that matter) is nowhere to be found on either of the 6 inverter PCBs. Since the only connection between the inverters and the rest of the TV is the Mystery 4-pin all white connector, that goes from the Master Inverter PCB to the T-Con PCB, I'd hazard a guess that the Main PCB sends the control signal to turn on the inverters (and receives the feedback "LAMP IS GOOD" from each of them) via the T-Con PCB. Am I correct in this assumption? If yes, how can I troubleshoot this further? Both boards are rather expensive to replace, and on top of that the Main PCB seems to be out of stock in the whole of the USA.
Since this TV set is huge and heavy I have to work in situ in a poorly lit room. I don't like to use flash on PCBs as it would provide more glare than useful information and I can't take pictures under natural light - it is just too dark in there. Moderators: do you feel it would be appropriate for me to use existing pictures of the very same boards from other posters floating around this forum?
Thanks in advance for any information!
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