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Hmm, got a Voltmeter?
If so, then you can see if the power supply is supplying power to the inverter board which lights up the lamps...if your TV's backlights aren't lighting up at all, then I'd see if the backlight inverter is getting power, and if the Power On command line is going active or not.
Here is a picture of your Inverter -- Take your black probe, connect it to GND, and measure Vin2 for 12/18/24 Volts.
Check ON/OFF...it should be either 0 or 5 Volts. That turns on the inverter like a light switch.
Tell us if you do get a constant voltage on the Vin, and whether you see the On/Off test voltage goes Hi and Low or not.
Of course it will all shut off when the Green light stops.....
Welcome back, did you run that test that I showed you?
I apologize, I somehow either missed your original response, or didn't get notified.
Vin2 - 24.63V
On/Off - Starts at .012V and only jumps to .2V at highest before shut down.
On/Off-- when it jumps, do you see the backlight lamps light up? There usually are slots on the back of the panel that you can see light come from. If there are none, then try to check the front of the panel, it's best to check it in a dim/dark room to verify.
IF they do not light up at all, we should disconnect the plug, put our voltage probe on the pin for the On/Off and see if it goes high/low or stays low.
Right now, it looks like the On/off line isn't turning on the backlight.
No backlight response at all.
Voltage on cable for On/Off with it unplugged is consistent with earlier readings. It appears to take a slight jump to approximately .1V just as system shuts down.
Meter is fairly quick (Fluke 12) however it isn't a recording meter so the .1v is approximate.
I was incorrect on the meter. It is a memory type. Max voltage at the On/Off is .380V
Ok, it looks like the main board isn't firing the inverters up at all. The plug that you were testing. It comes from the power supply board doesn't it. So it could be the main board or the power supply board dropping the Power on command. I know the main board doesn't mark the Pow_On line....Follow the cable back to the board it connects to. Look around the plug. On the board Sanyo usually marks the Pon or it may be labled as INV on (inverter on)
We need to determine if the Main board or the Power board is killing the power on line to the inverter.
We got our work cut out for us.
Right about now, I could use a picture of your entire chassis, a closer picture of your power board and one on your main board.
Let me see if I have an example of the reference or legends printed on some of the boards. Nope, the Sanyo markings are too basic to see an On/off line marked on them.
Ok, so this is what we'll have to do. Process of elimination.
The main board has one cable that connects to the power supply board. It's going to have the 5 volt standby, and a 12 Volt line or a 9 volt, or it may be 15. We will be looking for a 3.3 Volt or 5 Volt line that goes High and Low when the power button is pushed. You will find the line on a 10 wire cable connected between the Main board with all the input jacks, and the power supply board. You can eliminate any lines that provide the standby 5, the 9/12/15 lines, and of course the ground lines too. Anything else is CONTROL lines turning on the power supply/inverter or feeding back any inverter OK line. Look for one that fires up 3 times
Right now, I suspect the power supply board more than the Main board, simply because the power supply is more notorious for failures, but I like to check it as much as possible.
OK, where to start ??
The plug I was testing is actually a split harness with most of the wires going to the PS board and the rest going to the Main Board. The connection I was testing actually goes back to the Main Board as part of a 3 wire harness. Verified I was testing correct input by checking continuity from On/Off test pad to pin on plug.
I am including pictures of:
Close up of markings on PS board for cable going to Main Board
Hopefully pics come through OK, 1st timer attaching here.
A picture is worth a thousand words.....
This job would be soooo easy if every manufacturer would simply use pictures in their schematics.
Take a look at the barcode on your main board --