LG 32lc46 totaly dead

[vinceroger69]

Re: LG 32lc46 totaly dead

explaine please what multi meter setting i need it on?

[budm]

Re: LG 32lc46 totaly dead

Since the PFC Voltage boost did not make the Voltage on the Main DC filter go up, Iwould like to contentrate onthe PFC circuts as hown in the PDF, Iwould like to get the P/N of the U800? and a good close up picture in the red area, there should be a switched transistor that is turn on to supply the VCC to the PFC IC when the PS_ON is present. Please see PDF. If I uderstan you correctly the DC voltage on the two large balck eletrolytics caps (450vdc rating) in the primary side stay at 340vdc with the TV on or off?

[vinceroger69]

Re: LG 32lc46 totaly dead

yes the voltage stays roughly the same across the 2 caps tv on or off
U800 IS A
5501A
1DO7725
sorry cant get more pics at the minute my mate took them but will do as soon as i can
is there anything else i need to check for you?

[budm]

Re: LG 32lc46 totaly dead

Yes two caps are connected in parallel.
U800 IS A
5501A
1DO7725
These numbers doess not sound right, I need to Goolge it tonight.

[budm]

Re: LG 32lc46 totaly dead

OK, I found the spec for the PFC IC P/N 5501A, we need to check the VCC pin

[vinceroger69]

Re: LG 32lc46 totaly dead

boost diode part number is FSU10A60 mosfet for pfc is W20NM60
can i check the U800 as i only have a dmm is so where do i test and what settings does the multimeter go on?

[budm]

Re: LG 32lc46 totaly dead

You will be working in the AC primary side of the circuits which can be fatal, so be careful not to touch anything with your body, place the black probe of the DC meter to the neagative leg of one of the two large caps, this is the circuit ground point of the primay dc circuits, do not confuse this with the primary AC safety ground, the red probe will be on pin 8 of U800. Turn the power swithc of the TV to on and see if you get DC reading on this pin 8. I will need to get your good pictures later to find out who generate the VCC for pin 8 of this IC.

[vinceroger69]

Re: LG 32lc46 totaly dead

right will check this out for you tomorrow morning for you should be able to get pics as well for you will post readings up. cheers guys for your help.

[vinceroger69]

Re: LG 32lc46 totaly dead

well just done the test as you suggested and guess what 0 VOLTS will pop up to my mates in a bit to get better pics of that area you have outlined.

[vinceroger69]

Re: LG 32lc46 totaly dead

pics as requested

[vinceroger69]

Re: LG 32lc46 totaly dead

U502 is a KA78L 15AZ HI3 transistor
U500 is a ICE 3B 1565J

[budm]

Re: LG 32lc46 totaly dead

OK, looks like we are getting some where here, I will download your latest pictures and try to figure out where pin 8 of this U800 is connected to, it will not be easy since the board is not front of me to Ohm out the connection, you may have to do some probing for me.
I think it will be connected to one leg of the transistor close by, this transistor will act like a switch with one leg (more likely to be the Collector) connected the standby power supply extra DC supply, this transistor will turn on when the PS_ON is received.
The standby power supply transformer should have 3 winding on it, one is the primary drive winding, the second one is for the 5Vdc standby supply, the third (for 10~12vdc supply, this is not the same 12Vdc generated by the 12v/24v power supply) will be for self sustain of the standby power supply once the kick start is done, this voltage will be used for the PFC IC. I hope I am not confusing you on how the TV works.

[budm]

Re: LG 32lc46 totaly dead

OK, I look at the pictures, please see the PDF, you need to check the DC voltages as shown, you will be working on the HOT (LINE) side of the power supply and it is LETHAL, so take good precaution! You will have to connect the board back in place. You can solder some wires to those test points so you can take easier measurement, just make sure the wires will not touch ANYTHING else.

[vinceroger69]

Re: LG 32lc46 totaly dead

2f is wrote on that trasistor you cant read which earth point do i use? i will solder wires on it will be safer and easier for me.

[tom66]

Re: LG 32lc46 totaly dead

Use one of the negative terminals of the two big capacitors for ground.

[vinceroger69]

Re: LG 32lc46 totaly dead

cheers tom66

[vinceroger69]

Re: LG 32lc46 totaly dead

well guys it one of them days remember your words of wisdom test carfully as its the hot side well all was going well i soldered the wires on ready to test and relplaced the board in the set but i did not see as i plugged the mains lead in it had moved one of the wires and guess what it was touching the chassis so i have found one item defently short circuit says 639 uf1007 a diode but after replaced this and the fuse before i tested it again i read across the live and nuteral pins on the board by the fuse holder got a short circuit reading tested all items have now found a D3SRA60 device connect to a heat sink
it has four pins from left to right + squigly line squigly line - tested this out of circuit on the 2 squigly lines and - sign it reads short circuit in all directions so guess i need one of these before i can do more testing so guys any idea where i can get one from in the uk?
and yes leson learnt by me dont rush these jobs check and double check before plugging in.

[tom66]

Re: LG 32lc46 totaly dead

well guys it one of them days remember your words of wisdom test carfully as its the hot side well all was going well i soldered the wires on ready to test and relplaced the board in the set but i did not see as i plugged the mains lead in it had moved one of the wires and guess what it was touching the chassis so i have found one item defently short circuit says 639 uf100f a diode but after replaced this and the fuse before i tested it again i read across the live and nuteral pins on the board by the fuse holder got a short circuit reading tested all items have now found a D3SRA60 device connect to a heat sink
it has four pins from left to right + squigly line squigly line - tested this out of circuit on the 2 squigly lines and - sign it reads short circuit in all directions so guess i need one of these before i can do more testing so guys any idea where i can get one from in the uk?
and yes leson learnt by me dont rush these jobs check and double check before plugging in.

Do you have a picture of the component that was damaged?

I have done this before. Twice, on the same board. It only blew the fuse twice, nothing else was damaged. That was lucky.

[vinceroger69]

Re: LG 32lc46 totaly dead

well we all by our own mistakes sods law it cost money though
best pic i could take it a D3SRA60 device connected to a heat sink
it has four pins from left to right + squigly line squigly line -

[tom66]

Re: LG 32lc46 totaly dead

That's a bridge rectifier. It can be replaced with a 600V 4A device, such as GBU4J.