Lg 50pj550 no STBY light

[dzyk2000]

Re: Lg 50pj550 no STBY light

OK. I have a feeling the component connected to the IC may be damaged at this point.
So I need the resistance reading of all the pins against GND pin.

gnd to pin 1 is more than 20Mohm or is error measure
gnd to pin 2 is more than 20Mohm or is error measure
gnd to pin 3 10Mohms
gnd to pin 4 15kohm
gnd to pin 6 2.30 Mohms

I expect in >10K range.
Did the old IC blow up or what?

just f302 blow up, ic still look good,

[budm]

Re: Lg 50pj550 no STBY light

the first time when I replaced the ic301 made it short at his pins with solder i think. (i dont know where exactly i saw just flame), f302 was burned, I checked all the nearby parts and I replaced the ic301 again with a new one.

OK. I have a feeling the component connected to the IC may be damaged at this point.
So I need the resistance reading of all the pins against GND pin.

[budm]

Re: Lg 50pj550 no STBY light

I expect in >10K range.
Did the old IC blow up or what?

[dzyk2000]

Re: Lg 50pj550 no STBY light

[QUOTE=budm;838987]That is quite low resistance on the VCC pin, it should be in a lot higher than that.
You tested that without TV plugged into the AC outlet, right?

now i have 2.66 kohms i think capacitors was charged on first check

[dzyk2000]

Re: Lg 50pj550 no STBY light

[QUOTE=budm;838987]That is quite low resistance on the VCC pin, it should be in a lot higher than that.
You tested that without TV plugged into the AC outlet, right?


Yes, many thanks for your help and patience

[dzyk2000]

Re: Lg 50pj550 no STBY light

Please see post 38.
We need to get the drive circuit working first.

I still need an answer to this question: "I changed 3br1565jf ... but I had a short circuit after the soldering". What is shorted out after soldering?

the first time when I replaced the ic301 made it short at his pins with solder i think. (i dont know where exactly i saw just flame), f302 was burned, I checked all the nearby parts and I replaced the ic301 again with a new one.

[budm]

Re: Lg 50pj550 no STBY light

now i have :
pin 1 drain - 333v
pin2 cs - 0V
pin3 BA - 1v
pin 4 VCC - 0,6V
pin6 fb - 0,13v

resistance is 1.30kohm

That is quite low resistance on the VCC pin, it should be in a lot higher than that.
You tested that without TV plugged into the AC outlet, right?

How about this?
"I changed 3br1565jf ... but I had a short circuit after the soldering". What is shorted out after soldering?

[budm]

Re: Lg 50pj550 no STBY light

Side notes about this power supply board per page 40, it indicates that without main board connected the SMPS will turn on automatically, I hope that is the correct information. If it is true once we get the standby power supply to work then everything should come on without main board connected, but right now we need to get the standby power supply working first.

[dzyk2000]

Re: Lg 50pj550 no STBY light

Your reported Voltage reading on the STBY SMPS IC:
3BR1565
pin 1 drain - 327v
pin2 cs - 0V
pin3 BA - 0,1v
pin 4 VCC - 0,5V
pin6 fb - 0,1v

The reading of 0V on the VCC pin indicating the internal charge pump inside the IC is not charging up the startup/running cap C307 connected to the VCC pin. That cap has to be charged up to 18V for the circuit to start.
What is the resistance reading between VCC and the GND pin?

now i have :
pin 1 drain - 333v
pin2 cs - 0V
pin3 BA - 1v
pin 4 VCC - 0,6V
pin6 fb - 0,13v

resistance is 1.30kohm

[budm]

Re: Lg 50pj550 no STBY light

Please see post 38.
We need to get the drive circuit working first.

I still need an answer to this question: "I changed 3br1565jf ... but I had a short circuit after the soldering". What is shorted out after soldering?

[dzyk2000]

Re: Lg 50pj550 no STBY light

BTW, I already see error in the training manual. I.E. page 35, 36, it shows the DC V on the fuse F302 (for protection if there is short circuit in the STBY section) for the standby power supply to be at 1.5V in stand by and at 388V in running mode. So how does the STBY POWER SUPPLY run at 1.5V on the filter cap C305? I guess no one caught that during training session.
I did not look at the whole thing yet in details to see if there are other errors.
According to the training manual, in Standby mode the standby power supply will be putting out 3.46V, when TV is turned on then it jumps up to 5.14V, looking at the trace on the bottom side of the board it looks like it is done by the switched Q351.

the thing is that q351 is being fed from t301. and I have no power at t301. t301 is powered by the secondary coil connected to f302 and drain ic301. but t301 has no output voltage, whats wrong here

[budm]

Re: Lg 50pj550 no STBY light

on the filter cap C305 i have 327v

That is what as expected and I explained.
You need to tell me what shorted out after soldering? also read my last post 38.

[budm]

Re: Lg 50pj550 no STBY light

Your reported Voltage reading on the STBY SMPS IC:
3BR1565
pin 1 drain - 327v
pin2 cs - 0V
pin3 BA - 0,1v
pin 4 VCC - 0,5V
pin6 fb - 0,1v

The reading of 0V on the VCC pin indicating the internal charge pump inside the IC is not charging up the startup/running cap C307 connected to the VCC pin. That cap has to be charged up to 18V for the circuit to start.
What is the resistance reading between VCC and the GND pin?

[dzyk2000]

Re: Lg 50pj550 no STBY light

BTW, I already see error in the training manual. I.E. page 35, 36, it shows the DC V on the fuse F302 (for protection if there is short circuit in the STBY section) for the standby power supply to be at 1.5V in stand by and at 388V in running mode. So how does the STBY POWER SUPPLY run at 1.5V on the filter cap C305? I guess no one caught that during training session.
I did not look at the whole thing yet in details to see if there are other errors.
According to the training manual, in Standby mode the standby power supply will be putting out 3.46V, when TV is turned on then it jumps up to 5.14V, looking at the trace on the bottom side of the board it looks like it is done by the switched Q351.

on the filter cap C305 i have 327v

[dzyk2000]

Re: Lg 50pj550 no STBY light

BTW, you did verify that the diode D351, 352 on the cold side of the standby power supply are OK, correct?

Tested d351 have 178 , d352 have 414 i dont know if is god value

[budm]

Re: Lg 50pj550 no STBY light

BTW, I already see error in the training manual. I.E. page 35, 36, it shows the DC V on the fuse F302 (for protection if there is short circuit in the STBY section) for the standby power supply to be at 1.5V in stand by and at 388V in running mode. So how does the STBY POWER SUPPLY run at 1.5V on the filter cap C305? I guess no one caught that during training session.
I did not look at the whole thing yet in details to see if there are other errors.
According to the training manual, in Standby mode the standby power supply will be putting out 3.46V, when TV is turned on then it jumps up to 5.14V, looking at the trace on the bottom side of the board it looks like it is done by the switched Q351.

[dzyk2000]

Re: Lg 50pj550 no STBY light

The reading of 327V on the Standby power supply filter cap C305 is corrected and as expected. But when you start reporting 380V on the main filter caps (C616, 617, 618) the that put doubt in my mind about your data.
1) So did you replace that SMPS IC? The reason I ask because I do not understand "I changed 3br1565jf ... but I had a short circuit after the soldering". What is shorted out after soldering?
2) Do my pictures match your board? This is important because I do not have your board in front of me to look at, all I have are pictures which make it hard to trace the circuits.

the first time when I replaced the ic301 made it short at his pins, f302 was burned, I checked all the nearby parts and I replaced the ic301 again with a new one.

[budm]

Re: Lg 50pj550 no STBY light

BTW, you did verify that the diode D351, 352 on the cold side of the standby power supply are OK, correct?

[budm]

Re: Lg 50pj550 no STBY light

i have two multimeters, i know is imposible but is corect read 327 v dc.
in p813 socket i have 0v on all pins.

The reading of 327V on the Standby power supply filter cap C305 is corrected and as expected. But when you start reporting 380V on the main filter caps (C616, 617, 618) the that put doubt in my mind about your data.
1) So did you replace that SMPS IC? The reason I ask because I do not understand "I changed 3br1565jf ... but I had a short circuit after the soldering". What is shorted out after soldering?
2) Do my pictures match your board? This is important because I do not have your board in front of me to look at, all I have are pictures which make it hard to trace the circuits.

[budm]

Re: Lg 50pj550 no STBY light

Based on the pictures of the board I provided:
D301, 302, 306, 309 are connected in series to form rectifier for the incoming 230VAC.
The Cathode of the D309 is connected to the FUSE F302, the output side of the fuse is connected to the positive leg of the main filter cap C305 for the standby power supply section. The DCV on the C305 should be around 325VDC in standby mode.
When the TV is turned on, the PFC Voltage will be present on the main filter caps of the main power supply section, this boosted Voltage is then fed to the standby power supply section via D308 (Anode is connected to the (+) leg of the main power supply filter caps C616, 617, 618 so at this point the Standby power supply is running off the PFC boosted Voltage, this will put D301, 302, 306, 309 in reverse bias mode so they are no longer conducting, they will go into conduction mode again when TV is turned off.