42lg2100 dead, no standby led help

[Diah]

Re: 42lg2100 dead, no standby led help

dick_barton

i can see also the wiring socket from PWB to main borad not really sitting in its place lol

[sousavti]

Re: 42lg2100 dead, no standby led help

not shorted
ic801

top pin 0v
midlee 3.2v
bottom 5 volts


803

all 0volts


ic1500 the left one

3.3v on right side
middle and left side both 0 volts

[sousavti]

Re: 42lg2100 dead, no standby led help

dick_barton

i can see also the wiring socket from PWB to main borad not really sitting in its place lol

it is the connector is broken on top but its making contact

[dick_barton]

Re: 42lg2100 dead, no standby led help

What are the numbers on
IC801
IC803
IC1500

[sousavti]

Re: 42lg2100 dead, no standby led help

801:

d11 90D
17-33g

803

d119ce
17-18g

ic500

6p 910

[Diah]

Re: 42lg2100 dead, no standby led help

when you have 3.3v on mains then go the IR board at front of the TV are there 3.3v or not,

[sousavti]

Re: 42lg2100 dead, no standby led help

on ir board on front i get several wires that come from the main, and the i have a plug that has 4 wires that goes to the buttons

the labels on ir board that come from the mainboard are:

led r
led b
ir
gnd
5v-st
gnd
key2
key1

i have 5volts on 5st 5v on ir

3.3v on key 1 and 2

when i press key1 3.3v drops and then comeback again.. nothing happens on tv also if i press buttons of input volume etc it drops and comeback again...

when i press again with probe on key2 3.3v stays there

[dick_barton]

Re: 42lg2100 dead, no standby led help

IC801 is a 3.3V regulator and appear to be working (5V in and 3.3V out)

IC803 is a 1.8V regulator which is not getting any supply voltage and I suspect this provides the supply to the main processor IC. Did you check it with your meter for strange readings?


I've no idea what IC1500 is but it says 12v detect alongside

[sousavti]

Re: 42lg2100 dead, no standby led help

strange readings where?

[dick_barton]

Re: 42lg2100 dead, no standby led help

I think the 1.8V regulator should be supplied by the 5V standby but I have no circuit diagram so I am thinking that maybe the input of the 1.8V regulator is faulty or some of the capacitors around it are failing. However without the service manual I cannot really offer any real advice.
Perhaps someone on the Forum has a service manual.

[sousavti]

Re: 42lg2100 dead, no standby led help

here is the link of the service manual for the 32lg2100



mine is 42lg2100

i think is the same almost

what you think ?

[budm]

Re: 42lg2100 dead, no standby led help

What is the P/N of that IC806?

[budm]

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...

That connector is double -row pins so:
You have:
NC pinX, and P-DIM pin 24
A-DIM pin 21, and ERROR pin 22 (they are separated pin) this error pin is for the Inverter Error signal form the Collector of SMD Q382(?).
NC pinX, and INV_ON/OFF pin 20.
So which one is showing the 3V the A-DIM pin or the ERROR pin? Both of them?
The error signal may stop the main board from sending the PS-ON command, need to get the correct service manual to verify.

BTW, the regulator IC803 probably will not get any Input Voltage until IC806 is turned on.

And what are the numbers as printed on the barcode sticker of the power supply-Inverter board?

[budm]

Re: 42lg2100 dead, no standby led help

After doing the research, so I believe your power supply board is
LG EAY57681301 Power Supply / Backlight Inverter.
Pictures are provided by shopjimmy.
Per shopjimmy the board is used in these models:

40LH4010-ZD BEKVLJG 42LH50-UA AUSVLHR 47LH40-UA 47LH30-UA 42LH50-UC AUSVLJR 42LH4010-ZD AEKVLJG 42LH4000-ZA AEKVLJG 42LH4000-ZA BEKVLJG 42LH4000-ZA AEKVLG 42LH40-UA AUSVLUR 42LH300C-UA AUSVLJR 42LH3000-ZA AEKVLJG 42LH3000-ZA BEKVLJG 42LH30-UA AUSVLUR 42LF11 42LF11-UA AUSVLJR

So I download the LH50 which uses the same similar power supply as yours from ELEKTROTANYA, to get the function of the power supply-inverter board, as you can see what should happen when you force on the power supply, so you may have more than one board problem.

[sousavti]

Re: 42lg2100 dead, no standby led help

exactly that what i did and the backlights didnt turn on.... thats why i think psu have a problem and also mainboard....

well i think is not worth it repair this this way...

thanks anyway... :\

[dick_barton]

Re: 42lg2100 dead, no standby led help

Check the resistance of the two backlight transformers. Make sure they are identical in resistance values. The primary side will probably be <1 ohm and secondary side a lot higher but they should be identical.
Do a good visual inspection of both and see if there is any sign of burning on them or discoloration on the underside of the circuit board where they are fitted.


Edit:
I have a power supply with the same transformers
Primary = 0.7 Ohms each
Secondary = 18.6 Ohms each

Have you checked the fuse in front of the 4 Mosfets?

[dick_barton]

Re: 42lg2100 dead, no standby led help

Check the 4 Mosfets on the heatsink closeby which drive the backlight transformers for short/open circuit.

What is the part number on the IC marked.

[dick_barton]

Re: 42lg2100 dead, no standby led help

Looking through my magnifying glass I believe the IC is a BD9215F.

Do the backlights come on no matter how briefly when you carried out the test as shown in budm's post #34?

If they did then: -
short pin 15 of the above IC to 0V
and then repeat the same test #34

This should give you a chance to see what is happening with the backlights.

[dick_barton]

Re: 42lg2100 dead, no standby led help

Reading your first post again:

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

Where you have the red circles on the transformer, each side should measure 18 ohms. If they measure 0 ohms then check the blue capacitors alongside to see if they are shorted.

[budm]

Re: 42lg2100 dead, no standby led help

Looking through my magnifying glass I believe the IC is a BD9215F.

Do the backlights come on no matter how briefly when you carried out the test as shown in budm's post #34?

If they did then: -
short pin 15 of the above IC to 0V
and then repeat the same test #34

This should give you a chance to see what is happening with the backlights.

+1 and also verify that you do have 390VDC boosted Voltage to run the inverter circuit. It can be that the main board may be locked out by the error signal from the inverter circuit, you can verify that by Grounding the Error pin (0V = No Error) to see if you can get any action from the main board.