TV not powering on - with standby red –led flashing

[Willem01]

Hi all,

Error – TV not powering on - with standby red –led flashing
Model- LEDTV – 39T3500
Power boarD - shg3206a-101h

I have read through the Basic LCD TV and Monitor troubleshooting guides.
https://www.badcaps.net/forum/showthr...956#post305956, I am no ELEC engineer but can use a multi meter and soldering iron

In the meantime I could not see any damage to any caps on the cold side of the power board, so I have replaced all of them.

Unplugged the power connector on the board, I plugged the power cable in waited 30sec, plugged the connector back. The standby led remained on constant which showed me that it would power on..voila and it worked and we used it for longer than 2 hours. When I switched it off for longer than 40sec still in standby mode, it's flashing again and It would not power on, I had to disconnect the power connector again and got it to power up.
Then we left it overnight in standby mode, even if I disconnect the power connector and plug it back in again it still stays on a flashing standby led – it does not want to power on anymore.
I have measured the volts on pin- out's, with the gnd – poweron, bridged, I only get the 3.3v on both the rows, nothing for the 24v
The power connector is divided in two rows
DIM H-On….?
GND P-On…bridged
3.3v 3.3v….give me 3.3v
GND 24V…..nothing
24v 24v....nothing

What gave up as it did work before and now nothing again, what else can I look at, don't see any visual signs off blown caps as they are all still brand new just replaced them, cant give a high resolution pic now only a crappy low resolution from the web.
If anyone can give some advice, assistance would be appreciated

[dick_barton]

Re: TV not powering on - with standby red –led flashing

If you can post some photo's of your boards using the attachmnet would help.

[Willem01]

Re: TV not powering on - with standby red –led flashing

If you can post some photo's of your boards using the attachmnet would help.

I am not currently home, thought I could get some interaction while I get time to submit them later, much appreciated will upload later

[Willem01]

Re: TV not powering on - with standby red –led flashing

pics uploaded also the diagram

[dick_barton]

Re: TV not powering on - with standby red –led flashing

Disconnect the mainboard and use a 1K resistor and jumper between pin10 (P-ON) and Pin 7 or 8 (3.3V) and see if your 24V comes up
Use another 1K resistor and jumper Pin 7 or 8 (3.3V) to pin 12 (BL-ON) to see if the backlights come on. All on CON3.
The backlights also need the 24V supply to be working.

[Willem01]

Re: TV not powering on - with standby red –led flashing

Disconnect the mainboard and use a 1K resistor and jumper between pin10 (P-ON) and Pin 7 or 8 (3.3V) and see if your 24V comes up
Use another 1K resistor and jumper Pin 7 or 8 (3.3V) to pin 12 (BL-ON) to see if the backlights come on. All on CON3.
The backlights also need the 24V supply to be working.

What is the purpose for using the resistor, if you only bridge the pins out without the resistor what will happen

ns...I have no electronic background skills hence my question

[dick_barton]

Re: TV not powering on - with standby red –led flashing

If you were to make a mistake and connect between or to a wrong pin then you could damage the power supply. Example if you connected the 3.3V to ground then you may well have badly damageg the power supply. If you were using a 1K reistor then no damage would happen because the 1K resistor limits the current from the 3.3V supply to 3.3mA
(3.3V/1K = 3.3mA)

[Willem01]

Re: TV not powering on - with standby red –led flashing

Disconnect the mainboard and use a 1K resistor and jumper between pin10 (P-ON) and Pin 7 or 8 (3.3V) and see if your 24V comes up
Use another 1K resistor and jumper Pin 7 or 8 (3.3V) to pin 12 (BL-ON) to see if the backlights come on. All on CON3.
The backlights also need the 24V supply to be working.

I have done this and it returned 0 results nothing happens

[Chrille]

Re: TV not powering on - with standby red –led flashing

Check this thread out.
https://www.badcaps.net/forum/showth...48#post1022048

Another model though but it seems to be a similar problem.
I finally found a bad chip (MP2363DN).
Seems to be a common problem on Samsung TVs.

/Chrille

[R_J]

Re: TV not powering on - with standby red –led flashing

With the power supply disconnected from the main board. You have 3.3v standby so you should have +24v at L1 (jumper wire) If you do then connect P-on pin to 3.3v standby and see if you get +24v on Con3 pin 1,2 or 4

[Willem01]

Re: TV not powering on - with standby red –led flashing

I have bridged out the 3.3v and the P-On pins, then measured the volt readings on pin1, 2,4 and there is nothing.
Like you have explained with the power cord removed I still only have the 3.4v in standby.

[dick_barton]

Re: TV not powering on - with standby red –led flashing

What voltage do you have on the D(rain), G(ate), S(ource) pins of Q2 in standby and then when out of standby when you jumper P-ON to 3.3V using the 1K resistor

[Willem01]

Re: TV not powering on - with standby red –led flashing

What voltage do you have on the D(rain), G(ate), S(ource) pins of Q2 in standby and then when out of standby when you jumper P-ON to 3.3V using the 1K resistor

Hell for the heck of me I cant find Q2 on the board I only see Q4 is it that thing under the big heatsinks there are 2, which one of them....think I found something on the board but there is nothing mounted

[dick_barton]

Re: TV not powering on - with standby red –led flashing

The components may be on the other side of the board. Post a photo.
What voltage do you have at L1 to chassis.

[Willem01]

Re: TV not powering on - with standby red –led flashing

The components may be on the other side of the board. Post a photo.
What voltage do you have at L1 to chassis.

Aha...see when you know your trade you know your stuff found it

this is a pic taken earlier as i am not at home to check the v ,,,
will do so and report back.

[Willem01]

Re: TV not powering on - with standby red –led flashing

I will add the rest of the powerboard in a few pics split up to see better, kindly indicate where to find L1 and how to measure it with the multimeter ( where must I put the red and black leads )

You make me sound stupid - but I know nada of these electronic stuff

[dick_barton]

Re: TV not powering on - with standby red –led flashing

L1 is shown in the photo in post #13
Red meter lead on L1, black on chassis. Meter set to 20V DC

[Willem01]

Re: TV not powering on - with standby red –led flashing

L1 is shown in the photo in post #13
Red meter lead on L1, black on chassis. Meter set to 20V DC

8v

[Willem01]

Re: TV not powering on - with standby red –led flashing

What voltage do you have on the D(rain), G(ate), S(ource) pins of Q2 in standby and then when out of standby when you jumper P-ON to 3.3V using the 1K resistor

In and out of standby the voltage fluctuates from 7.5v to 8.3v

[Willem01]

Re: TV not powering on - with standby red –led flashing

With the power supply disconnected from the main board. You have 3.3v standby so you should have +24v at L1 (jumper wire) If you do then connect P-on pin to 3.3v standby and see if you get +24v on Con3 pin 1,2 or 4

V at the jumper wire fluctuates at 7.5 v - 8v,, when on standby or not , still zero volts on the 24v pins