So, a LED Tester can test the backlights without stripping the panel. 34USD with free delivery should get you one from here:
https://www.aliexpress.com/popular/led-tester-lcd-tv-led.htmlLike a voltmeter, + and - probes, applied between LED1 and Anode1 then LED2 and Anode 2 on connector LD3. Depending on the layout of the LEDs,
each application should light up one half of the LEDs, then the other half.
Your connector configurations are confusing me. You give the voltage table for A09. Do the leads in the loom mirror each other at the plugs or do some
wires in the loom cross over to different pins. Does this table show the actual pins in your TV and are you counting the pins from the correct end of the
plug. Usually pin 1 is identified in some way by an arrow head screen-printed on the board near pin 1 of the socket.
Going by your table, pins 2 (up to 3.41), and 4 (0.99 to 4.5 fluctuating) are the only pins behaving like a BL-ON signal, yet you say pin 12 = BL-ON.
Re capacitors, they don't actually give voltage, but they can store a voltage. Their upper voltage rating is stamped on the casing. This is the max
voltage that can healthily be applied to the capacitor. Any voltage over this will cause heat stress in the capacitor until it ruptures the top or bottom
casing. Bruce