Dear Mr IseeDesignHer,
here 2 more pictures, one side looks messy but i think thats just not so nice enigneering in the factory.. Maybe. And for the rest i realy dont see any damage. Yeah, those blue things around the flexconnector to the Inner screen. One of them is a bit off, i only just saw when i took that closeby picture, bu ti dont see any leaking, i dont see any damage. It is just not totaly straight connected in the factory i think...when i carefully push on to try to make it straight, there is no manipulating about it. You just press the whole board down. So thats that.
Again, take your time my friend, if you have a big family, enjoy that, take care of them first; thats moest important. And thanks for al your help!!!! greetings.
You are doing a great job. You will succeed. BTW, the power supply board is really of excellent quality. A little old (check the date code on the label sticking out), so everything is wires-thru-holes and not SMD (Surface Mount Devices).
That is good news; it makes it much easier to repair!
I looked at all of your pictures and I didn’t see anything that looked like a failed component. Of course, there always can be failures that are invisible.
The last 2 pictures are of the ‘Flyback’ transformer. I’ll explain the chain of components a bit more at the end.
First, the discoloration around its terminals looks grungy but it is NOT the result of overheating or failure. The wire on the bobbin of the transformer are usually enameled copper wire, but, for high frequency transformers, the so-called ‘Skin Effect’ makes it more efficient to use multiturn or Litz wires.
Internally, the ends of these windings are sheathed in a fiber insulator that adds extra high voltage protection, and these short wires are multiple lead tinned or silvered conductors. This extra protection is necessary because there may be peak-to-peak voltages on the primary side of close to 1,000 Vac! The secondary is more like 200 V ac ppk; still dangerous. If you zoom in you can see the fibrous nature of the wrap applied to the transformer leads.
In a production setting, they just use heat to melt all insulating materials at the tips when they are soldered into the board. The HV sheathing is intended to go all the way to the PCB so as to avoid any possibility of arcing.
If you look very carefully, you will see that the underlying wires, colored silver by the solder, shows as being firmly wrapped around the PCB terminals that have metal pins going down thru the PCB. This discoloration is hard to avoid.
Nice eyes, though. That’s the spirit. Keep it up. I would say that the PCB definitely needs dust removal though. A spray can of nitrogen or even a shop hose will scatter those dust bunnies off to the true Easter destinations, and save you from repairing an arc or short down the road.
——— NEXT STEP ——-
I am uploading a closeup of one of your pictures (very good quality, BTW).
This picture shows both the edge connector for the ribbon cable that goes out to your LED arrays, but also an index key that explains what to expect on each pin. The connector is a 26 pin 90 degree board mounted locking connector. You have 12 LED array cables, each having a “+” and a “—“ lead, making 24 pins in total. There are two spares.
The spares are visible at one end of the connector. These are pins 1 & 2. They are not used, but they are super useful as they indicate where pins 3 & 4 are, and so on.
Now, the index table shows the mapping between the PS gizzards and the ribbon cable connector. You have 12 identical PS sections, organized 6 above and 6 below on your PS board.
Each of these 12 sections can be localized by zooming in on those big resistors {RED BLK BLK SIL BRN}. These are 2.00 Ohm resistors with a 1.0% error tolerance (1.98 to 2.02 Ohms).
Below each resistor, you will find a single rectifying diode. (BLK + SILVER), a small blue ceramic capacitor, a shared dual winding common mode filter choke (shared between CH! & CH2, for example) and, finally, a big square encased large capacitor (that is probably a multilayer polyester capacitor). This capacitor is probably 1 uF, 150 Vdc. It may be anywhere from 0.22 uF to 4.7 uF, but I’m guessing 1.0 uF.
If you look to the top left corner of these 12 repeated PS sections, you will see the secondaries of the flyback transformer. There are 3 heavier windings (that go to lower voltage, higher current additional supplies) are to the left, and then there are two windings at the bottom right of the transformer.
These two leads feed ground (GND) on one side, and the other side is connected to every single one of the 12 2.00 Ohm power resistors!
Resistor Color Code Calculator and Chart (4-band, 5-band or 6-band)
The flyback stores energy during one side or polarity when it is fed from the rectified mains voltage, and, on the other phase, its stored energy will come out on its secondaries. In your case, the direction of the diodes, and the positive polarity of the output voltages, indicate that this common connection (all the 2.00 Ohm ‘current sharing’ ballast resistors) goes POSITIVE during flyback.
The diodes catch this positive voltage (which is equal for all 12 separate supplies) and the spikey pulse is first filtered thru the chokes which supply inductance and finally by the big blue capacitor. Together, they make a LPF (Low Pass Filter), and that eliminates the high switching frequencies of the flyback regulator, keeping squirrels and gremlins out of the TV picture and backlighting.
SO, WHAT TO DO NEXT?
Download a copy of the zoomed in section of the picture you took that I am including here, and please print it out. Then, meticulously go to each pin and measure the voltages for all 24 pins, which are labeled PIN numbers 3 throu 26 as per the index table.
Half of the pins SHOULD read zero voltage. The alternating pins (with a “+” label on the index) should all read about the same voltage. All 12 (TWELVE) of them.
Make a table like this:
Pin 3. 95.7 Vdc
Pin 4. 95.7 Vdc
Pin 5. 0.0 Vdc
Pin 6. 0.0 Vdc
Pin 7. 95.5 Vdc
Pin 8. 95.5 Vdc
Etc., etc.
Pins #3 thru #26. Every one of them.
This will tell you precisely the health of your PS board.
If you do it with the cable unplugged, 12 of them should read the (roughly) same high voltage. If they do NOT all 12 read the same, then there is something wrong with the PS board.
Now, if you turn the TV off and plug the connector back in, knowing which pins are the ‘HOT’ leads means you only have to make 12 measurements.
Because of the nature of the 12 identically sectioned flyback (think of a flyback as a spring sitting underneath some flat surface but not touching it. If you compress it completely, and let go, it would expand to ~ twice the length, pushing up on the panel above it. If those panels have inertia, they will all rise together to about the same height).
If you get readings that are SLIGHTLY different when the LED arrays are plugged in and the TV is on, these differences will tell you pretty much everything that you need to know about the health of your LED arrays.
How?
Here’s how:
For a moment, ignore the fact that the flyback PS is pulsing - think of it as like a battery.
I am going to assume that your flyback PS is putting out a total of 96 Watts under normal to bright viewing conditions. You have 12 LED array cables, which means an average of 96/12 = 8 Watts each. 8 Watts at 96 Vdc = 1/12 of an ampere, or 0.083 A.
AVERAGE.
Now, since the flyback is only supplying a positive pulse part of the time (25% to 60% worst case, but lets assume 33%), then, because the PULSE of current is only there 1/3 of the time, the current that has to flow during that pulse is 3 times the average.
0.083A x 3 = 0.250A, or 250 mA.
250 mA thru the 2.00 Ohm resistors will drop 0.500 V during that positive pulse. The diode will drop another ~0.7 V (but it doesn’t behave like a resistor -its equivalent series resistance to INCREMENTAL changes in current is a minimum of 0.100 Ohms @ 0.25 A, plus a little ESR so maybe 0.2 Ohms), and then there is the choke, which (guessing) may be 1.8 Ohms.
2.00 + 0.200 + 1.800 Ohms = 4.00 Ohms.
4 Ohms x 0.25 A = 1.0 Volts.
This voltage drop is called the ballast voltage. This allows mismatches in the total series voltage of each LED array to differ by up to ± 0.25 Vdc, maybe more.
So, if EVERY LED arrays was working, the 12 ‘HOT’ voltages should all match to within 1/4 of a Volt, or ± 0.250 Vdc. (The LED array does see a DC voltage because of the LC filter described above. This is what you are measuring with the DVM.
OK, lets assume exactly HALF of your LED arrays are open, and not working.
Now your (assumed) 96 Watts is divided among only 6 LED arrays, so their average, and peak, currents DOUBLE. So does the ballast voltage. It now doubles to 2.0 Vdc.
In an ideal world, the open LED strings would measure 2.0 Vdc HIGHER than the working ones, quickly identifying who is coming down to breakfast, and who is never coming down for breakfast again.
The world is not ideal. There will be ringing artifacts on the flyback windings that will spike up the open outputs much more than by 2 Volts. You could have anywhere from the calculated 2.0 Vdc difference to as much as 30 to 50 Vdc difference.
That will depend on the actual waveforms of the PS and how well its so-called ‘snubber’ circuits are taming the beast. You could have a very narrow overshoot pulse that gets ironed out on the loaded outputs but flies straight thru the unloaded ones.
I wouldn’t leave your TV on for a long time when any of its panels are bad because the good panels (LED arrays) are getting much more current and power than they normally would.
To summarize, please make a table with these 24 pin voltages, both unplugged and plugged in.
Post those results and we can determine the health of both your PS board and your LED arrays.
Please look at the picture below to see the pin index table printed on the PCB.
Best of luck!