46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

[IIOSOH]

Hi,

I'm trying to fix a Philips TV [46PFL5507K/12] for a friend. A few seconds after turning it "ON" a hourglass appears and stays on the screen for around a second, then the screen goes black again, there is no picture nor sound when i connect via HDMI to my PC.

I've opened it up and took a few measurements, but i can't seem to find the correct schematic for this exact model. The official service manual has detailed schematics and info for pretty much every other TV from the series but just some generic information about this exact part number so i measured everything i think i could.

Is it possible that the TV turns off and enters some kind of protection mode because it can't light up the backlight LEDs?

Below is a photo of said measurements.

The backlight voltage (Connector 1316) is present only while the hourglass logo is visible then it drops to 0 - 0.1V.

Connector 1M95 connects the power board with the processor board - "RL OFF" on the photo is short for "red light off"

https://imgur.com/a/xiprY9B

PS:

Measurements are taken from the connectors on the power delivery board, i've measured some of the voltages coming out of the DC-DC converters on the CPU board and everything seems ok - 1.2V 1.8V 3.3V 5.0V etc.

[dskall]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

What does your backlight voltage go up to?

[IIOSOH]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

When measuring across the anode and cathodes:

C1 - 15.0 V
C2 - 0.06 V
C3 - 83.7 V
C4 - 83.7 V

But as soon as the "Hourglass" disappears the voltages drop down to 0 - 0.1V

[IIOSOH]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

There aren't any LED drivers in the circuit. The required voltage is coming out of the secondary windings of a coil, then goes through some diodes and capacitors and into the connectors.
I took the board out to have a good look at both sides and take some more measurements.
All diodes' forward voltage drop is 0.5V.
There are no shorts nor visible damage
I'm not sure how to measure the resistance of the secondary windings but by comparing the random measurements that i took - the leftmost windings generating the voltage on the two pins that measure 15.0V and 0.06V have the same resistance as the windings that generate the 83.7 on the other two pins.

Below is a photo of the board:
https://imgur.com/a/OeixC8Y

[ducky29]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

Its always a good idea to check the backlights. I have had a Philips in with the same symptoms.

[Diah]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

you have shorted BL LED on 2 line. TV went to shutdown mode... your front LED should have blink code thids set will work and BL come on with out screen... so you need to consider take out the screen.

[IIOSOH]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

Its always a good idea to check the backlights. I have had a Philips in with the same symptoms.

Thank you

I just found this forum and promise to read all the "Sticky" threads before asking dumb questions again, but do you think i can test them with a current source without disassembling the whole TV? And if yes, what current limit should i set for this kind of LEDs?

[IIOSOH]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

you have shorted BL LED on 2 line. TV went to shutdown mode... your front LED should have blink code thids set will work and BL come on with out screen... so you need to consider take out the screen.

Awesome, i thank you for you responsiveness

Do you by any chance know how the TV "knows" that a BL LED is shorted? There aren't any ICs on the board to monitor the current flowing through the LEDs, i did not find anything about how that's done in the service manual.

[Diah]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

Awesome, i thank you for you responsiveness

Do you by any chance know how the TV "knows" that a BL LED is shorted? There aren't any ICs on the board to monitor the current flowing through the LEDs, i did not find anything about how that's done in the service manual.

we are making the judgment regards yours info and VCC messurments you provided.. could be you did miss some things.

BL socket should be the probe in place at each line and then turn on the set. and see how high or low it go..

you didnt mentioned if the front LED indicator if it give blink code !!

and why it show sandglass uhr and not Philips logo as it should..
did you try if it go on or off by RC. and in case yes did you call menu and see the screen with torch light if there any sign on the menu there..

about the protect.. actually there are many kind of protect some the PCB will shutdown (PFC) go low if there are over load at secondary.. some are with BL error bin on the socket between MB &PCB goes high if there are error at BL.

[IIOSOH]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

we are making the judgment regards yours info and VCC messurments you provided.. could be you did miss some things.

BL socket should be the probe in place at each line and then turn on the set. and see how high or low it go..

you didnt mentioned if the front LED indicator if it give blink code !!

and why it show sandglass uhr and not Philips logo as it should..
did you try if it go on or off by RC. and in case yes did you call menu and see the screen with torch light if there any sign on the menu there..

about the protect.. actually there are many kind of protect some the PCB will shutdown (PFC) go low if there are over load at secondary.. some are with BL error bin on the socket between MB &PCB goes high if there are error at BL.

The front led indicator is "OFF", from the moment I apply mains power and it never turns on, unless i turn off the TV from the power button. But i think this is by design - TV on = front LED off.

I measured the voltages between the Anodes and Cathode at the connector when the TV is starting:

Anode - C1 = 15.0 V
Anode - C2 = 0.06 V
Anode - C3 = 83.7 V
Anode - C4 = 83.7 V

But as soon as the "Hourglass" disappears the voltages drop down to 0 - 0.1V

There is no blink code.

PS: My friend lost the RC

[Diah]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

C1 C2 shorted LED ziner diode.. i think you have edge BL.. try to plug out this 2 line from the socket and turn on messure the main socket 12V remain on or not

[IIOSOH]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

C1 C2 shorted LED ziner diode.. i think you have edge BL.. try to plug out this 2 line from the socket and turn on messure the main socket 12V remain on or not

The 4x 12V Pins on the other connector never go away, so it is probably just the BL supply that's turning off as a protection. I also measure a short between two of the diodes when the the BL is connected, the short goes away when i unplug it, but for some reason i can't measure the short on the connector.

[IIOSOH]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

The 4x 12V Pins on the other connector never go away, so it is probably just the BL supply that's turning off as a protection. I also measure a short between two of the diodes when the the BL is connected, the short goes away when i unplug it, but for some reason i can't measure the short on the connector.

I removed just the C1 and C2 pins from the BL connector, the voltages on the other connector remain the same but the "Hourglass" only appears for a split second now so i can't really measure anything.

[IIOSOH]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

I removed just the C1 and C2 pins from the BL connector, the voltages on the other connector remain the same but the "Hourglass" only appears for a split second now so i can't really measure anything.

In the photo photo below i have encircled the two shorted diodes (20 Ohm).
The short is present only when i connect the BL LED connector, and goes away when i remove it but i don't measure a short between any of the pins on the connector itself...

https://imgur.com/a/KUv3xJJ

I guess the best next thing to do is to take the TV apart.

I sincerely thank all of you for taking the time to help me

PS: It is 1:30 AM here so i should probably go to bed before touching the 230V line again .

[qinitram]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

Hi,
anything new in your research? I have almost the same TV 46PFL5537K/12 with exact the same symptoms. After switching TV on, hourglass appears just for less than a second. Sound and video (checked with torch) are fine but the backlight is turned off. No blinking error code during switching TV on by RC.
I was not able to measure anything on CN2-1316 for the short moment at the boot time. There is no voltage on C1-C4 later on. There is only 3.3V on BL_ON on CN4-1M95, other pins BL_DIM, BL_I_CTRL and POK are 0V. If I switch TV off BL_DIM goes to 3.3V I guess, don't remember anymore. Power board and main board seems visually to be fine so I would rather suspect BL LED strip. Do you know the part number of the BL LED strip, I haven't took TV apart yet 😊

[lotas]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

hi,
anything new in your research? I have almost the same tv 46pfl5537k/12 with exact the same symptoms. After switching tv on, hourglass appears just for less than a second. Sound and video (checked with torch) are fine but the backlight is turned off. No blinking error code during switching tv on by rc.
I was not able to measure anything on cn2-1316 for the short moment at the boot time. There is no voltage on c1-c4 later on. There is only 3.3v on bl_on on cn4-1m95, other pins bl_dim, bl_i_ctrl and pok are 0v. If i switch tv off bl_dim goes to 3.3v i guess, don't remember anymore. Power board and main board seems visually to be fine so i would rather suspect bl led strip. Do you know the part number of the bl led strip, i haven't took tv apart yet 😊

lj07-00998a

[qinitram]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

lj07-00998a

just 1 piece is enough? Just one BL LED strip for the TV?
Thanks.

[lotas]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

Yes, one, it already comes with a radiator, you can separately strip SLED 2012SGS46 7030L 64 REV1.0

https://aliexpress.ru/item/329010700..._source=aerkol

[qinitram]

Re: 46PFL5507K/12 - Shows a "Hourglass" logo then turns off the backlight - No sound

Just have changed the LED strip and now TV works again! Thanks for help!