Emerson LF501EM4F turn on then off.

[erickeri1234]

Someone just gave me this tv.
When I plug it in, it turns on it can see the Emerson logo then for a split second it it goes to the normal screen before turning off. When it turns off I speakers make a popping sound.
Hard for me to figure out main board or power board.

[CapLeaker]

Re: Emerson LF501EM4F turn on then off.

Is it the backlight just turning off, or is the whole TV that turns off, reboots etc.
If it is the later, I would say main board. There are EEPROM kits or main boards available at SJ.
Also try to unhook that IR sensor from the main board and see what happens.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

The tv turns off. I have to unplug it for it to turn back on but it will it again. Seems like a short on one of the boards.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

Is it the backlight just turning off, or is the whole TV that turns off, reboots etc.
If it is the later, I would say main board. There are EEPROM kits or main boards available at SJ.
Also try to unhook that IR sensor from the main board and see what happens.

The whole tv turns off. No reboot. I unhooked the ir sensor but still the same thing.

[dick_barton]

Re: Emerson LF501EM4F turn on then off.

Disconnect the power supply and measure the dc voltages as given on the board. 5V,3,3V,12V, 24V whatever they are.

[CapLeaker]

Re: Emerson LF501EM4F turn on then off.

On the main board there is a ribbon cable that goes over to the power supply. There is pin called PSon on the main board. Set your meter to DCV, put your probe between it and GND and observe what happens to that pin when it is off, when you turn the TV on and then when it shuts itself off.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

Disconnect the power supply and measure the dc voltages as given on the board. 5V,3,3V,12V, 24V whatever they are.

It's a little hard there is no 5v,3.3v, 12v, etc by the ribbon connector on the board. Only jumper pins close to the connector.
I see
all+3.3v
Amp+137
P-on+21v
P-on_h2

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

On the main board there is a ribbon cable that goes over to the power supply. There is pin called PSon on the main board. Set your meter to DCV, put your probe between it and GND and observe what happens to that pin when it is off, when you turn the TV on and then when it shuts itself off.

P-on_h2 shows 3.2v then goes to 0v when it turns off.
P-on+21v shows 21.1v then goes to 11.65v when it turns off

[dick_barton]

Re: Emerson LF501EM4F turn on then off.

Is the All3.3 voltage there and stable?

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

3.3v there but when it turns off it goes to 0v

[dick_barton]

Re: Emerson LF501EM4F turn on then off.

So you do not have any standby voltage? If that is the case you need to take a look at the power supply to find what the problem is.

[dick_barton]

Re: Emerson LF501EM4F turn on then off.

Have you run the power supply up disconnected from the main board to see what supplies on it are stable.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

Have you run the power supply up disconnected from the main board to see what supplies on it are stable.

Sorry I gave wrong info.
All 3.3v is there all the time. Even After it turns off, main connected and disconnected .
So I do have 3.3v

[dick_barton]

Re: Emerson LF501EM4F turn on then off.

OK so the 3.3V is your standby voltage. With the main board still disconected connect your 3.3V using a 1K resistor to P-on_H2 (I think) and check the other votages come up and if they are stable.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

So jump 3.3 to p-on_h2 with 1k resistor! I got to see if I have a 1k resistor. Does the wattage of the resistor matter?

[dick_barton]

Re: Emerson LF501EM4F turn on then off.

No, any 1K will do.

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

No, any 1K will do.

Im trying to jump it with a resistor that I'm reading 1.032 but I'm getting 3.3v at the end but once I touch the p-on_h2 it drops down to 0.57v

[erickeri1234]

Re: Emerson LF501EM4F turn on then off.

Ok I tested with a different resistor and jumped all3.3v to p_on-h2 and got 12v on 13v rail. And got 21v on the 21v rail..

[dick_barton]

Re: Emerson LF501EM4F turn on then off.

When doing the above test did the backlights come on and stay on?