Unknown issue with Panasonic LED TV.

[Mikeyboy2007]

Hi guys, I have a Panasonic TX-46AS740B TV here with a TNPA6011 power supply. The issue i have is when you power tv on the green light flashes and tv trys to boot up, LED panel flashes 3 times around 2 seconds apart then red standby light starts flashing. I have stripped screen out of tv and can see that when the LED panel is trying to switch on the entire bottom row of LEDs is out. I have swapped the led strips about and also swapped with brand new working ones and still the same issue. Anybody have any ideas what is going on ?

Help much appreciated, would be a good tv to just throw in the tip.

[R_J]

Re: Unknown issue with Panasonic LED TV.

Check the voltages on P4 plug pins 2,4,6,8,10 & 12. Monitor the pin while turning on the tv and see if one of the pins is either very high or at 0 compaired to the others.
If one pins it different, check that trace back to its transistor (IE: Q7806) and check the transistor and resistors (If Q7806, check R7851,R7881,R7882,R7802,R7864) (If Q7805, check R7850,R7879,R7882 etc.)
There is a schematic online

[Mikeyboy2007]

Re: Unknown issue with Panasonic LED TV.

Hi R_J thanks for reply. I checked pins 2,4,6,8,10 & 12.. as soon as you plug tv in it trys to boot up and pins 2,4,6,8 and 10 all around 7.5v then backlights fire up 2,4,6,8 all quickly spike to 24 before slowly dropping and pin 10 goes to 20v.. pin 12 has 0v at all so will check schematic and see what i can do. Im not too sure how to check a teansistor but google will be my friend today. And will also check out schematic.

[R_J]

Re: Unknown issue with Panasonic LED TV.

I would check the line between the power supply P4 pin 12 and the panel, It sure looks like an open led string or open connection somewhere.
The led voltage is supplied by a common point P4, pin 1,3,5 etc. then the return of the led strings connect to p4. 2,4, 6 etc.

[Mikeyboy2007]

Re: Unknown issue with Panasonic LED TV.

Had this one on hold as been away on holiday etc, but will check over the next few days and figure out whats going on and will update the thread.

[Mikeyboy2007]

Re: Unknown issue with Panasonic LED TV.

Ok, so ordered another power supply, when it arrived it was fitted but backlights flashed with that one and still missing voltage on pin 12. Now what i did notice is on the postive / negative going to the LED steip thats out is a different coloured possibly burnt connector. Could this be causing the issue ?

I have attached picture

[budm]

Re: Unknown issue with Panasonic LED TV.

It looks like cold solder joints so you end up with bad contact resistant. I would clean it up and apply Flux & new solder, I would do all of them instead of waiting for others to fail later on.