finlux 42flhk240bhd no backlight

[MikeyBe]

I've been given this TV because aparantly it does nothing except the flash the standby light. However, on closer inspection it does apparantly work - when I plug it in, you can see a faint logo displayed on the screen, but the backlight doesn't illuminate.

It's a 42" LED backlit model.

I'd be extremely helpful if anyone had any suggestions...

[budm]

Re: finlux 42flhk240bhd no backlight

Upload good clear pictures of the back side of the TV will be a good start so we will know what we are dealing with.

[MikeyBe]

Re: finlux 42flhk240bhd no backlight

Hope this is clear enough...

[selldoor]

Re: finlux 42flhk240bhd no backlight

ARRRGHHHHHH!!! its a Vestel
It is ok for the general layout but may need to see where the wires go that lead off to the left. Can you post a good clear picture of each board front for now though may need backs.

[MikeyBe]

Re: finlux 42flhk240bhd no backlight

Some more pics then. The wires lead to a connector right in the bottom left of the unit. I'd say they're for the backlight...

[selldoor]

Re: finlux 42flhk240bhd no backlight

Still not really clear enough - need more light but no flash. Anyway in pic 3 to the left of
centre there is a somponent with 18 legs can you read the part number on it.

Yes I think they are for the LEDs as well I was just wondering if it went via another board.

Just to check - this is not very old its not still under a guarantee?

[MikeyBe]

Re: finlux 42flhk240bhd no backlight

you mean at the bottom of the image, just left of center? It reads

MPS1333
MP3394S
D44T132.9

I've been given the TV as non-working, so I guess any warranty is pointless...

[selldoor]

Re: finlux 42flhk240bhd no backlight

Ok it is one of these, which means the voltage to the led string is quite low.
https://www.monolithicpower.com/Page...0a4&&ItemID=52
So meter on vDC200 black probe on a ground screw check the voltage on each pin on that socket middle bottom Pic 2 - you can see on the back not all pins are used.
I think you will need all the boards connected to do this.

[MikeyBe]

Re: finlux 42flhk240bhd no backlight

Some pins read 0V, others 0.3V - that's both with that particular cable connected or not...

[selldoor]

Re: finlux 42flhk240bhd no backlight

Sort of expected that
If you read the datasheet there is a pin on the 3394s labelled EN for enable - can you get at that to test it?

[MikeyBe]

Re: finlux 42flhk240bhd no backlight

Hmmm.

Vin and En are all at 0V.

[selldoor]

Re: finlux 42flhk240bhd no backlight

Really need a better picture of the back of the board take it near to a window plenty of light
required. You could also test the voltages on the legs of the 35v and 16v caps.
Meter on 200vDC
Next to test will be the diodes unless a better picture gives another dlue.

[MikeyBe]

Re: finlux 42flhk240bhd no backlight

Here's the best I can manage (I think...)

The row of 1000uF 16V caps all have 7.6V across them whereas the row below that of 330uF 35V have 0V across them.

Thanks.

[selldoor]

Re: finlux 42flhk240bhd no backlight

Yes that is a lot better thanks -wow and you found a voltage ! Not one I was expecting
but that is only to be expected on these boards.
What is the part number on IC303

[MikeyBe]

Re: finlux 42flhk240bhd no backlight

On the connector that goes to the other board, I can see the 7.6V, as well as 5V and I think 3.3V too.

I think IC303 says

ICE3BR0665J
H1330/E2Z
51343026501

Alas my eyesight isn't what it once was and I need to get the magnifying glass from work.

[selldoor]

Re: finlux 42flhk240bhd no backlight

Well my eyes are gone for today - looking at too many boards!!
That number is correct
https://cdn.badcaps-static.com/pdfs/...696da025f5.pdf

At some point I would like you to test the voltage on the VCC pin - according to the datasheet it should be between 10.5v and 25v.
As this is on the HOT side of the board you should use the negative leg of one of the pair of 450v caps as ground (Take care) - do it when fresh and use a RCD if you have one.

At the moment I have no idea what is wrong - just collecting information. One of our main TV gurus hates these boards as they are badly designed and built and they keep moving bits around and none of the sockets are labelled.
On that socket you found the 3.3 and 5v (which is great by the way) there is a pin that switches the back lights on and another that works the DIM
and one that switches on the power supply fully. If they are not working then the problem may lie on the main board. Ill look at it agains tomorrow and maybe we will get a bit more input from overseas tonight.

[MikeyBe]

Re: finlux 42flhk240bhd no backlight

The VCC pin of IC303 gives 11.4V

[budm]

Re: finlux 42flhk240bhd no backlight

A little expalnation on the function of the SMPS STBY IC ICE3BR0666J:
When the power is first applied to the board, the start-up cap on the VCC (pin 7) is charged through the Drain (pin 5) internal current source, when the Voltage on VCC pin reach 18VDC, then the IC will start running. Once the IC starts running, the VCC can be any value between 10.5 ~25VDC range, if it falls below 10.5V or above 25V, the under/over voltage protection will kick in.
Since he is getting the standby Voltages (if I read post 15 correctly) then IC is functioning.
What happen if he disconnect the LED cable (the one on the bottom center of the board), will the standby LED still blinking?
Also what DC voltage does he have on that cap laying on its side close to the LED connector? That cap is part of the booster circuit for the LED switching power supply.

[MikeyBe]

Re: finlux 42flhk240bhd no backlight

Thanks for the help...

To answer, the standby light flashes the same with and without the LEDs connected.

Also, the capacitor next to the connector reads 0V across it.

[budm]

Re: finlux 42flhk240bhd no backlight

Hmmm.

Vin and En are all at 0V.

So we have to trace to see where the Vin gets its Voltage from. I cannot really trace out the bottom side of the board, the pictures are not clear enough for my eyes.