42lg2100 dead, no standby led help

[dick_barton]

Re: 42lg2100 dead, no standby led help

Did replacing the boards solve your problem and which board(s) were causing you the problem?

[sousavti]

Re: 42lg2100 dead, no standby led help

well thanks anyway... in this case i have to replace both boards is not worth anyway....

thank you so much for all the help

[budm]

Re: 42lg2100 dead, no standby led help

We already know that the power supply/inverter board has problem.
So I have you ground out the error pin to see if you can get the main board to come on and see if you will get power LED to come on or not, so if it does not then you also have bad main board, that is the reason we are grounding out the error pin to verify if the main is also bad or not.

[sousavti]

Re: 42lg2100 dead, no standby led help

i do it anda inverter wont come on...

so psu has problem right ?

[sousavti]

Re: 42lg2100 dead, no standby led help

ok got it

tomorrow i tell you something

thank you so much for everything

[budm]

Re: 42lg2100 dead, no standby led help

No force on resistors in place and all the cables are back in place, what we are doing is just grounding out the error pin to see if you will get the main board to come on, IE, get the POWER LED to come on, we are trying to find out if the Error signal is locking out the main board from coming on or not.

[sousavti]

Re: 42lg2100 dead, no standby led help

ok budm but when i gournd the error pin with 100 ohms resistance to gnd, i take off the 10kohm resistor between +5v and gnd ? or i leave that one too ?

[budm]

Re: 42lg2100 dead, no standby led help

and the backlights come on?

if they come on what does tham mean ? and if they didnt?

also when i short this pin with ground with a 100ohm resistor, do i leave the 5v shorted to pwr on with a 10k resistor? or i just have to short the error pin with ground with a 100 ohm resistor ?

thanks

The ERROR (Invertr Error) signal is generated by the Power supply-invereter board to tell the main board that there is problem with the inverter circuit so the main board will shutdown the TV.
So you will have all the connectors hooked back up but you will GND the Error pin with 100 Ohms to GND so the main board will not be getting the ERROR signal, at this point you should be able to turn on the TV but you will still not have backlights since it is not working at this point as shown by the Error signal generated by the power supply-inverter board.
You have already verified that there is problem with the inverter circuits when you forced it on per service manual, we just want to know if you also have problem with the main board or main board is being shutdown due to the error signal.

[dick_barton]

Re: 42lg2100 dead, no standby led help

The idea is if you carry out the test as shown in post#35 and the backlights do not come on then your fault lies there so you need to check the inverter circuits and CCFL lamps.

If however your backlights comes on, then the fault looks like it's the main board.

[sousavti]

Re: 42lg2100 dead, no standby led help

and the backlights come on?

if they come on what does tham mean ? and if they didnt?

also when i short this pin with ground with a 100ohm resistor, do i leave the 5v shorted to pwr on with a 10k resistor? or i just have to short the error pin with ground with a 100 ohm resistor ?

thanks

[budm]

Re: 42lg2100 dead, no standby led help

You can ground that ERROR pin 22 to ground through a 100 Ohms resistor to simulate NO ERROR signal.

[sousavti]

Re: 42lg2100 dead, no standby led help

fuse ok, resitance on both 0 ohms, yes i disconnect the bulbs and still the same....

the problem is that pin is 3.3volts... so i cant short it to ground correct?

psu maybe faulty and also main like we said before...

[budm]

Re: 42lg2100 dead, no standby led help

"i disconnect the 3.3volts error wire and still not happening" You mean the error wire going to the main board?
You need to ground the ERROR pin (pin 22) since 0V = Good, the main board needs to see 0V on that ERROR pin.

[dick_barton]

Re: 42lg2100 dead, no standby led help

I don't think disconnecting the wire stops the error. It's shorting the Timing point on the IC that allows the inverters to be driven and not stopped in the event of an error.

Can you confirm exactly what the secondary side of the inverter transformers resistance is, which should be < 20 ohms each

Was the fuse closeby also checked?

Edit
If the secondary side is 0 ohms then the transformers would have to be short circuited. It's hard to believe that both shorted at the same time. Did you disconnect the connectors to the backlights alongside the transformers when you did the test?

[sousavti]

Re: 42lg2100 dead, no standby led help

+1 That's a good point if the meter was set to a high resistance range.

fluke is automatic range

i disconnect the 3.3volts error wire and still not happening

[sousavti]

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.

the backlights dont come on never

[sousavti]

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.

ics good, fuse,

transformers primary 0 ohms and secondary 0 ohms, i dessolder and they are not burnt underneath...

[dick_barton]

Re: 42lg2100 dead, no standby led help

+1 That's a good point if the meter was set to a high resistance range.

[budm]

Re: 42lg2100 dead, no standby led help

Reading your first post again:



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.

I wonder what Ohm scale he was using.

[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.