Lg 50pj550 no STBY light

**budm** · 07-14-2018, 05:13 PM

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** · 07-14-2018, 05:16 PM

Re: Lg 50pj550 no STBY light

Originally posted by budm

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** · 07-14-2018, 05:17 PM

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.

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**budm** · 07-14-2018, 05:20 PM

Re: Lg 50pj550 no STBY light

Originally posted by dzyk2000

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?

**dzyk2000** · 07-14-2018, 05:25 PM

Re: Lg 50pj550 no STBY light

Originally posted by budm

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.

**dzyk2000** · 07-14-2018, 05:29 PM

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** · 07-14-2018, 05:43 PM

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

**budm** · 07-14-2018, 05:48 PM

Re: Lg 50pj550 no STBY light

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

**budm** · 07-14-2018, 05:51 PM

Re: Lg 50pj550 no STBY light

Originally posted by dzyk2000

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.

**dzyk2000** · 07-14-2018, 06:09 PM

Re: Lg 50pj550 no STBY light

Originally posted by budm

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

Originally posted by budm

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

just f302 blow up, ic still look good,

**budm** · 07-14-2018, 06:21 PM

Re: Lg 50pj550 no STBY light

"gnd to pin 2 is more than 20Mohm or is error measure" That is CS pin where the <1 Ohm Source resistance is connected to, so that reading is not correct. I thought you had already verify that the resistor connected between CS pin and GND is OK.
I also indicated that your drawing on post 1 is wrong regarding to pin 2 (CS) pin.

**dzyk2000** · 07-14-2018, 06:24 PM

Re: Lg 50pj550 no STBY light

Originally posted by budm

"gnd to pin 2 is more than 20Mohm or is error measure" That is CS pin where the <1 Ohm Source resistance is connected to, so that reading is not correct. I thought you had already verify that the resistor connected between CS pin and GND is OK.

yes is 0.36ohm

**budm** · 07-14-2018, 06:27 PM

Re: Lg 50pj550 no STBY light

Originally posted by dzyk2000

yes is 0.36ohm

So why do you report the reading on pin 2 as:
"gnd to pin 2 is more than 20Mohm or is error measure" Check the solder connection between pin 2 and that resistor (R305), it sounds like you do not have connection between pin 2 and the leg of the resistor. Damaged trace?

**dzyk2000** · 07-14-2018, 06:29 PM

Re: Lg 50pj550 no STBY light

allready checked all the nearby parts, nothing damaged, can be something tired but looks good on test.

**dzyk2000** · 07-14-2018, 06:32 PM

Re: Lg 50pj550 no STBY light

Originally posted by budm

So why do you report the reading on pin 2 as:
"gnd to pin 2 is more than 20Mohm or is error measure" Check the solder connection between pin 2 and that resistor (R305), it sounds like you do not have connection between pin 2 and the leg of the resistor. Damaged trace?

trace is good, now i will reheat solder conections.

**budm** · 07-14-2018, 06:44 PM

Re: Lg 50pj550 no STBY light

You can easily verify that by checking the resistance between pin 2 LEG (not the solder pad that pin 2 is soldered on to) against each leg of the resistor.

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**dzyk2000** · 07-14-2018, 06:46 PM

Re: Lg 50pj550 no STBY light

Originally posted by budm

You can easily verify that by checking the resistance between pin 2 against each pin of the resistor.

is allright now 0.36 ohm

**budm** · 07-14-2018, 06:51 PM

Re: Lg 50pj550 no STBY light

So bad solder joints?
You might as well check the rest of the pins also.

**dzyk2000** · 07-14-2018, 06:54 PM

Re: Lg 50pj550 no STBY light

Originally posted by budm

So bad solder joints?
You might as well check the rest of the pins also.

so the soldering was ok, just that was the tight space and I probably got my hand off the pine

**budm** · 07-14-2018, 06:59 PM

Re: Lg 50pj550 no STBY light

Well, what happen when you power up board after fixing the solder joints?

Lg 50pj550 no STBY light

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