Toshiba 22EL833G with Vestel 17PW05-3

[budm]

Re: Toshiba 22EL833G with Vestel 17PW05-3

OK, I did not see the pin name in post 1. That is a big drop.
I also agree that he needs to provide the Voltage reading you requested: Does the 24 volts appear at D712/13? if it does see if those resistors R781/782 are used and if they are that they are ok.

[Gogan]

Re: Toshiba 22EL833G with Vestel 17PW05-3

D401 and Q401 seem good

24V appear on D712/713

R781/782 are not present, 24V comes directly from Q707 (FDC642P from schematics)

C747/748 are not present

PL706 Pin 1/2 have 24V on boot them go down

[Gogan]

Re: Toshiba 22EL833G with Vestel 17PW05-3

This is getting weird

All of a sudden i have steady +27V all the way to CN402 COM, 3.4V on CN402 PIN1-4, but still no backlight

PL706
PIN1/2 - 27V
PIN3 - 3.1
PIN4 - 2.2

[R_J]

Re: Toshiba 22EL833G with Vestel 17PW05-3

That looks like the boost circuit is not working, check if D401 is shorted, check if you have VCC on pin28 of U401
You need more than 24 volts to light the led backlights.

If you monitor the 24 volt point on CN401 when you first turn on the tv, is the voltage higher (ie 40v) then drop back down to 24v?

24 volts should turn off when in standby? if not Q707 may be shorted
It could be that Q707 was damaged before and not switching on the 24 volts to the backlight circuit.

You have a red arrow pointing to a 0Ω resistor, was it open?

[Gogan]

Re: Toshiba 22EL833G with Vestel 17PW05-3

That looks like the boost circuit is not working, check if D401 is shorted, check if you have VCC on pin28 of U401
You need more than 24 volts to light the led backlights.

If you monitor the 24 volt point on CN401 when you first turn on the tv, is the voltage higher (ie 40v) then drop back down to 24v?

24 volts should turn off when in standby? if not Q707 may be shorted
It could be that Q707 was damaged before and not switching on the 24 volts to the backlight circuit.

You have a red arrow pointing to a 0Ω resistor, was it open?

About the red arrow: The first times I was checking the circuit I'm pretty sure I've checked that 0Ohm resistor and it was OK. Last time I was doing a quick check it felt inconsistent and I closed it. (24V were still droping at power on after that). But looking at the schematic It could not be opened or I wouldn't have had the 24V at all.



D401 is not shorted, but I'm not getting voltage at Gate, so Source is 0

24V start at 25V when I turn on the TV, then it reaches 27.2V, standby kills it (as it should)

Back traces:
D401 body ->CN402 COM (25/27V)

Q401 Souce -> U401 PIN4 (0V)
Q401 Gate ->C410/R401 -> U401 PIN2 (0V)

[Gogan]

Re: Toshiba 22EL833G with Vestel 17PW05-3

Now I fell like a moron...

Set the TV aside for a few days and yesterday it hit me: I've never traced the 2.2V and 3.1V coming from the PSU on the TCON

CN401 PIN14 was bent (3.1V coming from PSU)


Guess the original problem got to do with the transformer, or a cold joint, or even that 0Ohm resistor

It's working again

Thank you all for the support!