LG 32lc46 totaly dead

[vinceroger69]

hi new to the forum today feel bad already asking for help but here goes.
i picked up a lg 32lc46 up from my local freecycle site (even came in original box with stand remote and power lead) the person said when i collected it she had a quote and its a power supply issue? so today i replaced all the caps all 19 of them ( used panisonic i think) just in case and guess what still as dead as a dodo lol as in no power leds nothing. i checked to see if i have 240 volts at the 5 amp on board fuse i do. so i now need your help fault finding i have resoldered any bad joints i could find using a x30 maginfiying lamp nothing remotly looks burnt or has any holes blew in it so can anyone help me with fault finding i only have a auto ranging multimeter no scope so can you help step by step with voltages to test etc and where to place the test probes correctly when testing etc i have the board out at the minute. the board number is EAX318450201/13 REV 1.2 cant upload any pics at the minute due to lending camera out to relative on holiday.

[tom66]

Re: LG 32lc46 totaly dead

Those two black capacitors - check that you get 160 - 320V across them. Are you in US or UK?

[vinceroger69]

Re: LG 32lc46 totaly dead

thanks for your reply iam in the uk right so i check the 2 largest caps in the power supply ie black multi meter lead on cap neg red on cap poss set multi meter on ac volts correct? cheers

[randtek]

Re: LG 32lc46 totaly dead

thanks for your reply iam in the uk right so i check the 2 largest caps in the power supply ie black multi meter lead on cap neg red on cap poss set multi meter on ac volts correct? cheers

Should be DC volts, not AC.

[tom66]

Re: LG 32lc46 totaly dead

Yes in the UK you should see 310 - 350V across those caps.

If you get that check the standby voltage - as you can't take pics look for anything labelled "STBY" e.g. 5VSTBY.

[vinceroger69]

Re: LG 32lc46 totaly dead

cheers guys just going to test now on dc volts report back in a min

[vinceroger69]

Re: LG 32lc46 totaly dead

yes 338 volt dc each now where to test the other voltage you mentioned do i put neg lead to a chassis screw on the power supply other on 5 volt test point?
found 2x st5v on a socket will test them now
yes just checked both have 5 volts says p201 on plug socket
any other ideas to check next
just check socket p202
19v 0 volts
19v 0 volts
gnd
gnd
6v 0 volts
gnd
3.4 0 volts
gnd
12v 0 volts
gnd
a bit more testing done top right middle in the pic i posted theres a white socket p204 wires go to invertor board marked 24 volts on 5 seperate pins no voltage to them is this because i cant get it to come out of standby?

[randtek]

Re: LG 32lc46 totaly dead

a bit more testing done top right middle in the pic i posted theres a white socket p204 wires go to invertor board marked 24 volts on 5 seperate pins no voltage to them is this because i cant get it to come out of standby?

Yes, you won't get those voltages until the power supply turns on. Look for a pin on the power to main board connector labeled PS-ON. Try connecting that pin to the 5v line through a 1k ohm resistor. See if your power supply turns on, and all voltages come up. (You should probably disconnect the power connector at the main board before doing this.)

[vinceroger69]

Re: LG 32lc46 totaly dead

found a pin that says on off right next to 5 volt pin just got to find a 1 k resistor now

[vinceroger69]

Re: LG 32lc46 totaly dead

just done that now and ps does not start my 5 volts i had before adding this load has gone down to 3 volts? with resistor as a load
edit a question should i be testing this with just the mains connected to the board all other connectors disconnected ie one goes to invertors 2 go to the other board.

[tom66]

Re: LG 32lc46 totaly dead

just done that now and ps does not start my 5 volts i had before adding this load has gone down to 3 volts? with resistor as a load
edit a question should i be testing this with just the mains connected to the board all other connectors disconnected ie one goes to invertors 2 go to the other board.

No need for load - this tells us all we need to know.

With this pull up resistor what is voltage across those big caps? Should be around 380 - 420V.

On the heatsink on the secondary side there are some devices. These are probably diodes. Check all the pins for shorts (<0.1V on diode test.)

[vinceroger69]

Re: LG 32lc46 totaly dead

both read 344 volts 2 different dmms
will test all the devices on the heat sinks on secondary side now
just checked all 7 none seem short at in tested in circuit not removed.

[tom66]

Re: LG 32lc46 totaly dead

both read 344 volts 2 different dmms
will test all the devices on the heat sinks on secondary side now

Hmm, did it increase from 338V? Could just be mains voltage fluctuations. Pretty common.

The fact that the PFC didn't start up is important, but more important is why the rails aren't there. Even with bad PFC there should be some voltage. The PFC might not be starting up because it is powered from the main rails in some way, but I'm not certain.

Listen carefully to the power supply. Do you hear a faint ticking sound when you attempt to turn the power supply on with the resistor?

[vinceroger69]

Re: LG 32lc46 totaly dead

yes increased by 6 volts under load just edited my last post no ticking what so ever under load or with all connectors on
on the connector i am placing the resistor load on it says
adc
on/off
st/5v
gnd
i-c
err
i-b
st/5v
gnd
dim
6v
gnd
3.4 on
i have been placing the load between on/off and the st/5v
is this correct?

[tom66]

Re: LG 32lc46 totaly dead

Okay - no shorts.

Here's where a picture would be helpful. On the board there's likely to be a controller IC. I would highlight it if you have a picture of the back side of the power supply.

[vinceroger69]

Re: LG 32lc46 totaly dead

see my above post please i will look at board now and get back to you how big is this chip on primary or secondary side? of board
primary side are these 5501a_id07725 8 legged
0001-h26 8 legged
location u101 cant read 8 legged
secondary side 62t03gh
725504 diode?
u3037m
705523
does this help? can i get a diagram to get part numbers values etc

[budm]

Re: LG 32lc46 totaly dead

Good pictures of the connectors, so we see the labels on them, good closed up of the bottom side and top side of the board, also closed up of all 1/4 section of the board.
That will help a lot if we need to trace out the copper traces.

[tibimakai]

Re: LG 32lc46 totaly dead

usually when there are no rail voltages, the controller is bad?

[budm]

Re: LG 32lc46 totaly dead

Here are the service manuals, one of these should match your chassis.
http://elektrotanya.com/?q=showresul...oria=&kat2=all

[vinceroger69]

Re: LG 32lc46 totaly dead

could someone help me find the controller ic part number can this item be tested using a dmm?
will post pics up but leant camera out as in first post wont get back untill monday.