TV not powering on - with standby red –led flashing

[dick_barton]

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

What dc voltage do you have at R17 (0 ohm resistor)

Set your meter on with a range suitable to read the voltage between the two legs of C1 which is rated at 450V dc and let us know what it reads when P-ON is activated.

[Willem01]

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

What dc voltage do you have at R17 (0 ohm resistor)

Set your meter on with a range suitable to read the voltage between the two legs of C1 which is rated at 450V dc and let us know what it reads when P-ON is activated.

R17 - multimeter voltage= 0.03 en 0.0
C1 - multimeter voltage = 317v - 320v

[dick_barton]

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

It looks like your PFC circuit is not working which is why the secondary voltages are not correct.

With the mainboard disconnected from the power supply what dc voltage do you have between the two legs of C5 (or C6) on the power supply when you power up with the jumper connected to 3.3v to P-ON.

Be carefull that the meter probes do not slip since this is on the high voltage side of the power supply.

[Willem01]

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

It looks like your PFC circuit is not working which is why the secondary voltages are not correct.

With the mainboard disconnected from the power supply what dc voltage do you have between the two legs of C5 (or C6) on the power supply when you power up with the jumper connected to 3.3v to P-ON.

Be carefull that the meter probes do not slip since this is on the high voltage side of the power supply.

Must I measure on the green lines as in the pic for C6

[dick_barton]

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

The capacitor does not need to be removed. You just measure the dc volts between the two points that the legs are soldered to the board so the answer is yes but put the capacitor back in the correct way around. The capacitor has a positive and negative leg Also don't forget to jumper P_On to 3.3V standby.

[Willem01]

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

With the power disconnected and the P ON jumped,, it reads 12v

[dick_barton]

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

The power must be connected or you can't have 12V?

[Willem01]

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

Must I connect the power
Ok with the power connected it measure 12.3v,

I have heated up the board with a hairdryer and measured the pin outs on CON3 and they are all working as it should... Why is it working now

[dick_barton]

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

With the mainboard disconnected from power supply and the 1K jumper resistor connected between P-ON and 3.3V, connect the power to the power supply board.
Measure the voltage across that capacitor and take care when making the measurement.

[Willem01]

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

The power must be connected or you can't have 12V?

???

[Willem01]

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

This is how it currently is, connected to power and all measurements on CON3 are in spec with the P-On bridged

[dick_barton]

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

So connected like that at switch on the voltage across the capacitor measures 12.3V or does it go higher then drop and repeat?

The initial voltage to charge the capacitor at switch on comes from U1 which should charge the capacitor to 16V minimum to start the circuit oscillating that will then provide the secondary supplies.

[Willem01]

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

Ok so I f#@ed up not been carefull and shorted these with the test probes

[Willem01]

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

So connected like that at switch on the voltage across the capacitor measures 12.3V or does it go higher then drop and repeat?

The initial voltage to charge the capacitor at switch on comes from U1 which should charge the capacitor to 16V minimum to start the circuit oscillating that will then provide the secondary supplies.

With the power connected it stays on 12.3v,when piwer is disconnected it starts draining down to 9v or as long as I keep the multimeter on it it goes lower

[Willem01]

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

I put the board back in the tv and connected all the plugs and it switched on, to test it I unplugged the power from the wall socket for 1 minute, plugged it back in and have the led flashing led again and would not turn on, only until I bridge the P-On and 3.3v with power connected remove it and connect all connectors and power cord, then it switches on.
@dick_barton thanx for all your help so far until I get the part

[dick_barton]

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

Hello Willem01,

I put the board back in the tv and connected all the plugs and it switched on, to test it I unplugged the power from the wall socket for 1 minute, plugged it back in and have the led flashing led again and would not turn on, only until I bridge the P-On and 3.3v with power connected remove it and connect all connectors and power cord, then it switches on.

I don't quite understand what you are trying to say here. What part are you waiting for?

[Willem01]

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

When I done the test on C6 I accidentaly touched the Mosfet Q4... caused a short

I was at the electronic shop they tested it and still works

I soldered the heatsink and mosfet back into the board,, with the 3.3v and P-ON jumped and the power cord connected there is now a humming noise on the board and no readings on CON3, so I f&#@ed up��

[dick_barton]

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

Do you still have the 3.3V and if so what voltage do you have been the two legs of C1 or C2 with and without the jumper P-ON to 3.3V in place.

I must admit that if the Gate and Drain pins on the mosfet were shorted out, then I cannot understand how it could have survived.

With the set powered off set your meter to ohms and check ZD3, D10, R26, R28, R29, R30 and R31

[Willem01]

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

Do you still have the 3.3V and if so what voltage do you have been the two legs of C1 or C2 with and without the jumper P-ON to 3.3V in place.

I must admit that if the Gate and Drain pins on the mosfet were shorted out, then I cannot understand how it could have survived.

With the set powered off set your meter to ohms and check ZD3, D10, R26, R28, R29, R30 and R31

There is no reading for the 3.3v
C1 and C2 reads 315v for pinned and not pinned
Ohm readings for
ZD3... 00.4ohm
D10..25ohm
R26..00.5ohm
R28..510ohm(meter set to 2000ohm)
R29..18.7ohm
R30..25.1ohm
R31..00.7ohm

[dick_barton]

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

Either the gate/ source of the mosfet is short circuit or more likely the zener diode ZD3.
You need to lift off ZD3 and make a note of which way around any markers are so it goes back in the exact same position. Then check its resistance when out of circuit.


Can you post a photo of that area so I can see the components mentioned.

R30 looks as though its a 100 ohm resistor so I think D10 is probably damaged as well

I would double check the mosfet as shown in many Youtube videos for example
https://www.youtube.com/watch?v=gloikp9t2dA