Panasonic led tv 55ds500

[thuss]

Hi

The tv turns on for a couple of seconds the screen looks fine and then it switches off and turns on again displays on the screen and then switches off.

The standby red light flashes approx once every 3 seconds. Ive read up somewhere its the led driver board or the led strips.

Can anyone advise me on how to distinguish between the driver board or the led strips (without having to take the screen out)

The psu powers the led driver board which powers the led strips and the mother board? in series

I disconnected the led strips from the led driver board but the tv wouldnt switch on.

Any pointers would be appreciated

[thuss]

Re: Panasonic led tv 55ds500

heres the photo with a view of the rear of the tv

[budm]

Re: Panasonic led tv 55ds500

So what kind of Voltage testing have you done so far?
BTW, the pictures are too blur to help troubleshooting the problems.

[thuss]

Re: Panasonic led tv 55ds500

I didnt get a chance to test any voltages my multimeter packed up after testing components on the led driver board tnpa6073- I think its a faulty transformer bottom of photo number 5, My phone camera isnt what it used to be soz

[budm]

Re: Panasonic led tv 55ds500

LED driver board: That is an inductor for the boost converter circuit for driving the LED's strings (8 strings).
Right now we cannot tell much until we get some supply Voltage readings and control Voltage readings from you + good clear pictures.

[thuss]

Re: Panasonic led tv 55ds500

will do thanks - I should have seen the L symbol.

Do you mind if I ask how I should test this 8 string inductor. Theres 5 legs on one side and 3 legs on the other ?I assume all should read with very low resistance?

only the centre leg (on the three side) bleeps with all the 5 legs.

the two outside legs individually (on the three side) read with two legs on the 5 side.

Hope the above makes sense.

Im getting values from 0.6 ohms to 480 ohms

[thuss]

Re: Panasonic led tv 55ds500

ignore previous post - completely misread Budm's post.

[thuss]

Re: Panasonic led tv 55ds500

I cant see any voltage tables written on any board.

But going back to the led driver board the inductor (sorry about the blurry photo)

In bleep mode

Leg 1 to leg 2 no bleeps 486 ohm
leg 3 to leg 4 Bleep 0.5

Leg 4 to leg 1 Bleep 0,5
Leg 2 to Leg 4 OL reverse probes 486


Desolder the inductor

Leg 1 to Leg 2 OL
Leg 3 to leg 4 OL

Leg 1 to Leg 4 0.5 Bleeps
Leg 2 to leg 3 OL

Is the above normal? I think its failed

[budm]

Re: Panasonic led tv 55ds500

We need to do Voltage testing but without good clear pictures I cannot tell you where to test.
Do not waste time looking at that inductor.
Right now we do not even know if the power supply is putting out correct Voltages and if the main board is sending out the correct control Voltage or not.

[thuss]

Re: Panasonic led tv 55ds500

I hope the following helps if I start with the voltages on the psu left hand side of the plug going to the right

wire 1- 24.65 wire11- 24.65
wire 2- 24.65 wire 12- 24.65
wire 3- 0 wire 13- 24.65
wire 4- 0 wire 14-0
wire 5- 15.65 wire 15- 0
wire 6-15.65 wire 16- 15.65
wire 7- 0 wire 17- 0
wire 8 - 0 wire 18- 0
wire 9- 5.18 wire 19- 3.28
wire 10- 2.66 wire 20- 3.28


LED DRIVER BOARD LED connector Voltages

connector 1 top middle left (DC)

wire 1 red 79
wire 2 red 79
wire 3 red 79
wire 4 red 79
wire 5 black 3.4
wire 6 black 3.4
wire 7 black 44
wire 8 black 44

connector 2 led driver board

wire 1 red 79
wire 2 red 79
wire 3 red 79
wire 4 red 79
wire 5 black 44
wire 6 black 44
wire 7 black 44
wire 8 black 44

mainboard voltages connector block

wire 1 3.25 wire 8 0.11
wire 2 3.21 wire 9 3.32
wire 3 2.66 wire 10 3.25
wire 4 5.19 wire 11 3.27
wire 5 0 wire 12 0
wire 6 15.65 wire 13 0
wire 7 15.65 wire 14 15.65

Any pointers would be appreciated

[budm]

Re: Panasonic led tv 55ds500

Based on some of the Voltage readings, it looks like 24VDC is the input Voltage to feed the LED backlights power supply, then it is boosted (by that boost converter circuits which that inductor is part of the circuits) to 79V to drive the LED strings.

'connector 1 top middle left (DC)

wire 1 red 79
wire 2 red 79
wire 3 red 79
wire 4 red 79
wire 5 black 3.4
wire 6 black 3.4
wire 7 black 44
wire 8 black 44'
Those that show 3.4V look suspicious.
This is where LED tester for testing the LED strings come in handy.BTW, what is the TV full model number? Is it TX-55ds500??

[thuss]

Re: Panasonic led tv 55ds500

Yes the model number TX-55ds500b. I did think the 3.4 were way to low.
Basically I think its time to remove the screen to access the led- something I hate doing on the 55 inch screens I just find it a bit to cumbersome.

I can get my hands on a led tester-can I unplug the connector and the connect the red to wire 1 and black to wire 5 and so on or is that wishful thinking?

[budm]

Re: Panasonic led tv 55ds500

If you have LED tester then you can easily test each LED string via the LED connector, you just have to pair (red and black wires) it correctly to the tester.

[thuss]

Re: Panasonic led tv 55ds500

If you have LED tester then you can easily test each LED string via the LED connector, you just have to pair (red and black wires) it correctly to the tester.

If I understood correctly without taking the screen out.

I just pair the wires from the back of the to the led tester.

Based upon the voltages do you think the led driver maybe faulty?

I suppose what I could is disconnect the led strip connectors from the led driver board and see if it makes difference to the voltages.

If the 3.4 value increases then I know the backlights are dragging the voltages down

[budm]

Re: Panasonic led tv 55ds500

Just remove the LED connectors from the LED driver board and test 8 sets of the LED string, you will have to figure out which Red wire and Black wire to to connect to the LED tester to test each LED string.
Can we see good clear pictures of the back side of the LED driver board around the LED connectors?
Based on your readings, the 79V is the feeding Voltage to all 8 anode (all 8 anodes of the LED strips should be tied together) pins of the LED strips, the Black wires are the Cathode return for the LED strips, eacjh one of the LE Cathode return goes to PWM Controlled MOSFET and current sensing resistor then to circuit GND..
The LED tester will tell you if those two LED strings (one with 3.4V) are good or not.

[thuss]

Re: Panasonic led tv 55ds500

Still waiting to get my led tester back - Does anyone know what the voltage values should be for the led driver board?

Just out of curiosity I unplugged the leds from the driver board and I got the following results

All the red wires pins had more that 70 to 90 plus volts on them.

All the black wires started to read 3.4v.

Does anyone know what the voltages on the driver board should be - thanks

Ive got the service manual - but I cant seem to find the output on the led driver board to led

[budm]

Re: Panasonic led tv 55ds500

Look at the Voltae rating oeach one of those tow lytics caps willl give you the idea as what the Voltages should be.

[budm]

Re: Panasonic led tv 55ds500

"The tv turns on for a couple of seconds the screen looks fine and then it switches off "
What is the Voltage rating of that biggest cap on that LED driver board?
The boosted Voltage you have right now is correct otherwise you not see the image on the screen.

[thuss]

Re: Panasonic led tv 55ds500

Biggest cap is rated at 63v.

One thing I forgot to mention the connection (right hand side of led driver board) the last black wire disconnected is reading -0.1v whilst all other black wires 3.4v

Arent the black wires anodes?

[budm]

Re: Panasonic led tv 55ds500

That is why you need to provide good clear pictures of top and bottom side of the board so we can see the circuit connection, we can spend days or months on this board without the good clear pictures.
So what is the small one rated at?
BTW, you did use chassis GND for the meter when you measure all those Voltages, correct?