Blinking stby led on a TD systems TV with 17IPS11 PS

[edugimeno]

Hi There!
I have a TV set (model TD Systems K32DLV1H) which doesn't power up.
During power off, the stby red led is on, as it should, then I press power button on remote and the led starts blinking, endlessly.

Sounds to me like a PS problem. TV is kinda alive as it stays in Stand-by, recognizes power up button from remote, etc, but can't really power up.

Internal PS is a 17IPS11. First inspection shows no damaged components, no swollen caps, and multimeter shows all diodes are good. Also there's a dual diode transistor shaped component on a heatsink that measures ok, and also a (probably) mosfet on another heatsink measuring no shorts on any pin

Being lead by other forums it makes me believe it could have to deal wih the backlight. Now the question is, how can I determine, without removing the LCD panel, if the issue is with the LED strips themselves, or the LED voltage generator in the PS? Or maybe you guys can provide any other hint on what to check?

Any help would be greatly appreciated!!
Thanks

[dskall]

Need pictures of boards and connectors. Voltages from power board to main and led in standby and when powered up. You may be able to unplug t-con and power up might bring up backlights. You can tap screen to see if backlights are working. Also use flashlight to see if there is an image on screen.

[arizanotlari]

Hi.

Turn-on the tv and Check led voltage. If voltage around 70V-90V replace led bars.

[edugimeno]

Originally Posted by dskall

Need pictures of boards and connectors. Voltages from power board to main and led in standby and when powered up. You may be able to unplug t-con and power up might bring up backlights. You can tap screen to see if backlights are working. Also use flashlight to see if there is an image on screen.

Ok I will check this tomorrow as right now I have the PSU board out for further tests
Thanks!

[edugimeno]

Originally Posted by arizanotlari

Hi.

Turn-on the tv and Check led voltage. If voltage around 70V-90V replace led bars.

I did test this before I took the PSU board out, it measured 19v. Short in the LEDS?

[arizanotlari]

No. unplug led cable from psu. connect probs to led socket. turn-on tv and measure the voltage at the first moment.

[edugimeno]

Ok I got some measurements
All this is assuming that the verson on my PS is this one:
https://elektrotanya.com/vestel_17ip.../download.html
(mine is using the 2x6 connector enclosed in a box)
Before power up measurements:
(1) "PIN1": 0v
(3) "STDBY": 2,5v
(5) "BLON_OFF": 0v
(7) "PWM_DIM": 0v
(9) "STBY_ON": pulsing around 250mV
(11) "+12v": +12v
(13) "+12v": +12v

Then when I power it on:
(1) "PIN1": 0v
(3) "STDBY": 0v
(5) "BLON_OFF": 0v
(7) "PWM_DIM": 3,3v
(9) "STBY_ON": pulsing around 130mV
(11) "+12v": +12v
(13) "+12v": +12v

Now about LED power. It doesn't matter if I have the wire plugged to the leds or not. 0v when stdby, that rises to 20v when triting to power on. No higher pulses than 20v.

Someone asked to try with T-con removed, this set doesn't have a T-con board. But I tried while the ribbon from MAIN to LCD was unplugged with no changes.

Thanks everyone!

[dskall]

Looks like maybe a mainboard problem.
Ok looking at pin 9 should have 5v I think. So maybe power supply. I am not good with schematics. Maybe someone else ccan jump in with schematic knowledge.

[edugimeno]

Mainboard? Why do you think that? I still believe it's the PS

[Diah]

Originally Posted by edugimeno

Ok I got some measurements
All this is assuming that the verson on my PS is this one:Thanks everyone!

yours measurements could be error.. can you disconnect the MB from the PCB totaly. just plug in wall and give yours new measurements on the socket which it goes to MB !!

[arizanotlari]

Pin 3 and 5 not good. I misunderstood your problem at first. If the standby led is blinking continuously, there is a problem with the motherboard.

[edugimeno]

The stdby led blinks only when I try to power it on, but it stays lit when powered off (as it should). Once I try to power it on, it blinks, and then there's no way to power it off again (getting it to solid lig again) unless I unplug it from mains and plug it back in

My measurements varied just a little when I tried with MB unplugged. I still believe it's the PS, as I don't even get +5v on STBY_5V when unplugged from MAIN board

[edugimeno]

Originally Posted by edugimeno

(9) "STBY_ON": pulsing around 250mV

Sorry PIN 9 is labeled "+5V STBY" on the schematic. I don't get this voltage

[arizanotlari]

Pin 9 is not connected, forget it.

What is mainboard name?

[arizanotlari]

I give you a tip: if you connect 12V 1A adapter to pin 1 (ground) and pin 13 (plus) motherboard working without psu. You can test mb this way.

[nomoresonys]

maybe check the electrolytic caps closest to the connector and check all the diodes, does seem like your standby voltage is looking funky.

[nomoresonys]

pictures would help.

[Diah]

Originally Posted by edugimeno

My measurements varied just a little when I tried with MB unplugged. I still believe it's the PS, as I don't even get +5v on STBY_5V when unplugged from MAIN board

MANNN... how it come your measurements varied just a little when the MB unplugged ???? how it come you have 12V on the socket and the MB didn't send any power on signal.... can you explain...???? there are no power boards work from alone to provide operation VCC 12V with out power on... LOL

[arizanotlari]

Originally Posted by Diah

MANNN... how it come your measurements varied just a little when the MB unplugged ???? how it come you have 12V on the socket and the MB didn't send any power on signal.... can you explain...???? there are no power boards work from alone to provide operation VCC 12V with out power on... LOL

Some Vestel boards do that. 12V always on. Other 3 signal send from mb to psu.

[Diah]

Originally Posted by arizanotlari

Some Vestel boards do that. 12V always on. Other 3 signal send from mb to psu.

so you mean at this PCB the 12V always active... then the MB should have stepdown circuit to let the SPI run 3.3V to send signal back to PCB via the OPTO to run PFC hight >400V to provide the T to work and provide AC -- to DC 24V for LEDS BL. only this i can imagine it. so funny design... would better to them to let it work with external transformer...