42lg2100 dead, no standby led help

[sousavti]

hi all

tv model 42lg2100

psu model: eax 55357701/32

what happens is:

i connect the main cable power nothing happens completly dead, no standby led nothing... then i measure the +5v of standby and i got 5v on standby voltage, if i disconnect mainboard
i still got the 5v standby but no led on front

so what i do is to disconnect the mainboard and turn on psu with a 10k resitor shorted between +5v and pwr on, then i connect maisn cable again with the mainboard disconnected and measure
the voltages and i got all voltages, +5v +12v and plus 20v, also on inverter error i got 3 volts more or less, so i assume the psu is working....
i connect again mainboard and i put multimeter on the 5v line and when i press the button i notice that the voltage drop to 2 3 volts and back on to 5v when i release...

this board has inverter in it so what i do next is disconnect mainboard again, short +5v with pwr on with a 10 resistor to turn on psu and then i short with a wire the pwr on with the inv on
to see if i have backlights... and i dont have... so the psu is working but i cant have backlights...

on the board there is two inverter transformers, when i measure the primary it gives 0ohms, when i measure primary vs secondary it gives OL but when i measure the two pins on secondary side i get 0 ohms...
on both transformers

here is the image where i get 0 ohms reading:

http://postimg.org/image/keloc3vor/


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each transformer has 2 pins underneath where i put the red circle i think it is the secondary because it goes straight to the lamps after that...


is the inverters shorted? or this is normal ? i dont know if i should replace the mainboard or the psu ? can you help me please ?

thanks so much

[budm]

Re: 42lg2100 dead, no standby led help

EAX is the blank PCB number, the PCB assembly should be EAY?????????. What numbers are printed on the barcode sticker?
Right now we at least know that the main board is not sending the PS-ON to turn on the power supply board.
The backlights may not come on without the Dimming signal.
Can see the pictures of the whole back side of the TV and the pictures of the whole board?

[sousavti]

Re: 42lg2100 dead, no standby led help

how do i send the dim singal» do i have to short it too ?

[sousavti]

Re: 42lg2100 dead, no standby led help

when i press the on button the voltage 5v drops to 2 3 volts and then back to 5v.. maybe something is shorted on psu no ?

[comptek]

Re: 42lg2100 dead, no standby led help

please post a picture of the full power supply

bright clear images of front and back thank you

[sousavti]

Re: 42lg2100 dead, no standby led help

ok here it is...

i only need to know if to turn on the inverter is just short the pwron with inv on ?

is it normal to have 0ohms of measure on both sides of the both transformers on the secondary ?

http://s24.postimg.org/49of2du5x/IMG...403_200946.jpg

http://postimg.org/image/g1cad6os1/


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[dick_barton]

Re: 42lg2100 dead, no standby led help

What are the labels on the pins and what voltages do you have on each.

[sousavti]

Re: 42lg2100 dead, no standby led help

ok labels are:

nc p-dim
a-dimerroe
nc inv on/off
20v
gnd
12v
gnd
5.2v
5.2
gnd
gnd
nc power-on

with psu off i have all 5volts only

with psu on with a resitor of 10k ohms shorted between 5v and nc power on i have all 5v 12v ands 20v

on a-dim error i got 3 volts more or less...

[dick_barton]

Re: 42lg2100 dead, no standby led help

So it looks as though the power supply is working.
If you reconnect the power supply back to your mainboard but disconnect the wire Power_On that comes from the mainboard to the power supply and measure the voltage on that wire.

[sousavti]

Re: 42lg2100 dead, no standby led help

i connect the plug normal, and disconnect the wire pwr on on the psu? then i measure the voltage on that pin on mainboard ?

do i have to press the button on off when i measure the voltage ?

[sousavti]

Re: 42lg2100 dead, no standby led help

i connect the plug and disconnect the wire pwr on on plug on psu, i measure voltage on wire it gives 0.001 or 0.002 volts...

if i press on off button it still gives the same....

[dick_barton]

Re: 42lg2100 dead, no standby led help

You need to measure the voltage on the Power_ON wire coming from the mainboard (not the power supply) when you switch the set on.

[sousavti]

Re: 42lg2100 dead, no standby led help

its what i told you...

it gives no voltage 0.001 volts.. the set is all connected and i disconnect the pwr on wirecomign from the mainboard

if i press buttons nothing happens voltage still the same....

i dont have nothing on front no standby led nothing.. is completly dead...

[Diah]

Re: 42lg2100 dead, no standby led help

how do i send the dim singal» do i have to short it too ?

never do such mistake, you have fault on main board, DC to DC conversation, i don't have the service manual of it, but you can follow the wiring of 5 volts on main boards. and put here your thought.

[sousavti]

Re: 42lg2100 dead, no standby led help

i didint short it

on service manul it says to replace on chip really small its impossible to get this ic...

i think its better to replace all main then...

is it normal dont have the standby led ?

[dick_barton]

Re: 42lg2100 dead, no standby led help

Sorry but just checking that you were measuring the voltage coming from the mainboard and not the voltage on the Power_ON pin on the power supply.
If you have no voltage being sent to the power supply from the mainboard then it would indicate that your mainboard is at fault.

Can you post a sharp image of your mainboard. Perhaps one of the voltage regulators are faulty.

[sousavti]

Re: 42lg2100 dead, no standby led help

yes i measure on the wire coming from mainboard, and i disconnect on psu

here is the image where the cable enter so i assume is those regulators you talking no ?

http://postimg.org/image/ceftsvxnl/


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[Diah]

Re: 42lg2100 dead, no standby led help

its okay dear dick_barton yours suggestion always i read here as wise one and exact reasonable facts too

[Diah]

Re: 42lg2100 dead, no standby led help

yes i measure on the wire]

could you put the link of the service manual, or upload it here,,, lg main boards are doubled sides not easy to talk on photo

[dick_barton]

Re: 42lg2100 dead, no standby led help

The two regulators I can see are marked although there could be more on the circuit board that are not shown.

Can you check what voltages, if any you have on each one. Also check that they are not shorted.


Edit
I have missed out IC801