Seiki SE39UY04 Main board AND Tcon board bad?

[R_J]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

Using the SJ photo, It looks like the t-com VCC is switched by Q30 on the rear of the main board, so check the voltage on pin 1, pin 8 and pin 5(gate)

[jayjr1105]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

Using the SJ photo, It looks like the t-com VCC is switched by Q30 on the rear of the main board, so check the voltage on pin 1, pin 8 and pin 5(gate)

Pin 1 - 12.7v
Pin 5 and 8 were 0.3v

Keep in mind, I have the original mainboard which can be harvested for parts.

[R_J]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

Pins 1,2,3 - 12v is good
Pins 6,7,8 - 0v means the fet (switch) is not turned on
Pin 5 is the gate, 0.3v is likely not enough voltage to turn on the fet
Something is not telling the fet to turn on and supply the t-con voltage.

[jayjr1105]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

That's all I need to hear really. I'll go back to the ebay seller of the board and ask for another one. I just wanted confirmation really. Thanks for the troubleshooting steps.

[budm]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

Does pin 5 change state when toggling TV on and off?
Most of the time they will use P-CH for this 12V switching for T-CON VCC, so the Gate Voltage has to about 4V < the Source pin Voltage for it to be ON.

[jayjr1105]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

Another main board came in today. Same exact issue. Ugh!

I just ordered a T-Con board for $9. Is there a possibility the LCD is bad? FWIW the new main boards at least turn the TV on. The original main board wouldn't let the set be turned on.

[Diah]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

.

[jayjr1105]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

So pin 5 and 8 on Q30 should give me ~2v with the tcon board disconnected?

[budm]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

Again, does pin 5 of the MOSFET change state when TV is turned ON and OFF?

[jayjr1105]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

Again, does pin 5 of the MOSFET change state when TV is turned ON and OFF?

When shut off, Pin 5 goes down to nothing. Takes a while, I assume it's capacitors draining.

Well guys my amateur a$$ is throwing in the towel. New main board, new TCON, power supply voltages are all fine. Set powers on, standby light goes from red to blue, backlight comes on but no picture. I have no idea if it's something really simple or if the display itself is bad.

[nomoresonys]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

Take a good look at the driver/tab bond board/s, check the cof (chip on film) on the flex cable for discoloration or being very hot, maybe test the caps on driver board for shorts.

[jayjr1105]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

Backlight is good. I assume that's what you mean by driver board.

I suppose it could be a bad ribbon cable. Where is the COF?

Just another interesting thing... When I power it on and leave it on, 20 minutes later it's turned off again. I assume it turns off after not receiving input? That tells me the "brains" are working. I don't have the remote sadly.

Edit: Also, when plugged in it pulls about 8 watts from the wall, when turned on it jumps to around 65 then settles around 43. Measuring with a kill a watt meter

[nomoresonys]

Re: Seiki SE39UY04 Main board AND Tcon board bad?

This here, not English but has subtitles, requires some disassembly, MUST BE VERY CAREFUL when near the panel, they are very very easy to break, if panel breaks/cracks then it's game over: https://www.youtube.com/watch?v=P0nsEaR9YgA