LG 32lh20r

[wrongpolarity]

Hi All,

The set is not responding to the remote or power push button. Red led remains on with no activity or clicking of relay.

I have checked the POWER_ON signal at pin 2 of P201 of the power supply but it remains Low all the time despite activating the power push button repeatedly.




To confirm that the Microcontoller is indeed receiving the signal from the power pushbotton, the voltage at Pin 240 KEY1 changes from 3.35V to 0.18V when the power push buttom is activated.




I went on to check Pin 229 RL_ON of the Microcontroller which provides the POWER_ON signal to the power supply but there were no activity when the power push button is activated.



All my findings tells me that the mainboard maybe faulty but I cannot be sure until I have done further measurements with a scope which I have back ordered and is due to arrive anytime.

My next course of action would be to:
-Measure the crystal of the Microcontroller to ensure operation.
-Reflow the fine pitch Microcontroller with soldering iron and lots of flux.Yes I have an oven but I will get divorced if I bake the board in the oven

Any other suggestions or ideas ?

Thanks.

[vinceroger69]

Re: LG 32lh20r

can you use a 1 k resistor between ps on and 5v just too make sure your psu the outputs the other voltages but yes does sound like a mainboard issue.

[dskall]

Re: LG 32lh20r

Might go around and verify your mainboard voltages are correct. That you get a reset signal to processor. Maybe you could post a link to schematic

[wrongpolarity]

Re: LG 32lh20r

can you use a 1 k resistor between ps on and 5v just too make sure your psu the outputs the other voltages but yes does sound like a mainboard issue.

Thanks for the response, I will get hold of some 1k resistor and pullup the ps_on to high.

Might go around and verify your mainboard voltages are correct. That you get a reset signal to processor. Maybe you could post a link to schematic

Thanks, here's the link for the service manual:



I have verified the voltages on the mainboard and they are all present. May I ask under what condition should I get a reset signal, when I hit the power on button ?

All,
Some additional information, I tried spray freezing the serial flash ram IC802 as suggested in some forum but the TV still won't power up

Thanks

[budm]

Re: LG 32lh20r

What DC Voltage do you have on that ERROR pin that comes from the power supply board? May be that ERROR signal from the power supply board is locking out the main board from sending out the PS-ON signal, I am not 100% sure yet since I did not download the service manual to find out if the ERROR signal is implemented in this TV or not.

[dskall]

Re: LG 32lh20r

Each time you power up. The processor has to be reset to load first instruction