Need help with Samsung LN40E550f7f

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Ok can you jumper blu_on a5 and and ps on together?

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Jumped it. No backlight.

You jumped it plugged in tv and turned on tv right?

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

no luck?

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Starting to suspect your power supply board.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Theres some power supplies on ebay for 75 bucks, seems too high for a 40 inch tv tho. explains why theres so many lol. when you can find tvs on sale for 200 or so, thats like half the price of a whole tv.

[Kindred1]

Re: Need help with Samsung LN40E550f7f

You jumped it plugged in tv and turned on tv right?

Yes I did.

[Kindred1]

Re: Need help with Samsung LN40E550f7f

Ok can you jumper blu_on a5 and and ps on together?

Just to be clear, blu_on, A5 and PS_on?

[Kindred1]

Re: Need help with Samsung LN40E550f7f

Theres some power supplies on ebay for 75 bucks, seems too high for a 40 inch tv tho. explains why theres so many lol. when you can find tvs on sale for 200 or so, thats like half the price of a whole tv.

I've found them cheaper. I just want to find out why the BLU_on is 0 volts.

[budm]

Re: Need help with Samsung LN40E550f7f

The BLU_ON is from the main board.
>2.5VDC = Backlights circuit ON
<1VDC = Backlights circuit OFF.
So when you disconnect the cable from the power supply board to the main board and use the resistor between A5V and BL_ON is to simulate the ON signal.
Per your reported reading on the PS-ON pin and the DIM pin without the cable connected those signals are present due to pull-up resistor built into the power supply board, so that part of the power supply board is OK. If you look at the BL_ON pin right now with the resistor in place, you should then see >2.5V on that pin due to the resistor is being use to simulate the bl-on signal, it is present, right?

[Kindred1]

Re: Need help with Samsung LN40E550f7f

Hi Budm. - So you're saying with the jumper in place between a5 and blu-on, ( connected to the cable that connects to the main board) Check blu_ on for >2.5volts?

[budm]

Re: Need help with Samsung LN40E550f7f

Hi Budm. - So you're saying with the jumper in place between a5 and blu-on, ( connected to the cable that connects to the main board) Check blu_ on for >2.5volts?

Yes.

[budm]

Re: Need help with Samsung LN40E550f7f

BTW, that white fuse next to the main filter caps are OK, right?
That fuse provides 380VDC boosted Voltage to run the Inverter circuit.
I hope you do not have two problems:
1) Main board not sending BL-ON signal.
2) No backlights when forced on.

[Kindred1]

Re: Need help with Samsung LN40E550f7f

I must not be checking the right spot. I put the lead on blu_on pin at the power supply and get 5.17. My meters lowest setting for ohms is 200. I'm going to get my toner that has continuity tester.

[budm]

Re: Need help with Samsung LN40E550f7f

I must not be checking the right spot. I put the lead on blu_on pin at the power supply and get 5.17. My meters lowest setting for ohms is 200. I'm going to get my toner that has continuity tester.

Since you are not using the resistor on the the BL-ON pin thus it will show the same Voltage reading as A5V, the bottom line is that BL-ON pin is showing >2.5V which is more than enough to turn on the circuit.

[Kindred1]

Re: Need help with Samsung LN40E550f7f

BTW, that white fuse next to the main filter caps are OK, right?
That fuse provides 380VDC boosted Voltage to run the Inverter circuit.
I hope you do not have two problems:
1) Main board not sending BL-ON signal.
2) No backlights when forced on.

fuses are good

[Kindred1]

Re: Need help with Samsung LN40E550f7f

Since you are not using the resistor on the the BL-ON pin thus it will show the same Voltage reading as A5V, the bottom line is that BL-ON pin is showing >2.5V which is more than enough to turn on the circuit.

O.K. So, what's my next step?

[budm]

Re: Need help with Samsung LN40E550f7f

Just to be sure with the test setup as it is right now, please verify that you do have about 380VDC between the two legs of the main filter cap (you can shcek on either one of them since they are connected in parallel).

[Kindred1]

Re: Need help with Samsung LN40E550f7f

Just to be sure with the test setup as it is right now, please verify that you do have about 380VDC between the two legs of the main filter cap (you can shcek on either one of them since they are connected in parallel).

Both reading 368v. With jumper still in place. Now I may have misunderstood directions early on. I reconnected power to main, but one end of jumper in the blu_ on lead in the plug. I do get proper voltage. Both ends. Sorry if I screwed up.

[budm]

Re: Need help with Samsung LN40E550f7f

Both reading 368v. With jumper still in place. Now I may have misunderstood directions early on. I reconnected power to main, but one end of jumper in the blu_ on lead in the plug. I do get proper voltage. Both ends. Sorry if I screwed up.

"but one end of jumper in the blu_ on lead in the plug. I do get proper voltage. Both ends." I do not understand, so you have jumper install between BLU_ON pin and the A5V pin while the cable between the power supply and the main board is still connected?

[Kindred1]

Re: Need help with Samsung LN40E550f7f

No. Forget the 'jumper'. What I meant was used a piece of wire to get get access to the pin ( in between plug housing and wire) because my meter leads are too big. The used a meter to get a reading off the wire. - When I mention misunderstanding directions, I was referring to when you first had me checking voltages off the board early in this thread.