Need help with Samsung LN40E550f7f

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

would the backlights stay on if the CCFLS are ok with the main board disconnected or just flash for a split second which is what they are doing with the main board disconnected.

They stay on, when pullup resistors are present, usually means backlights and powerboard are ok.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Do test on post 180.

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

when i hit the power BLU_ON goes to 5.16v and drops to 5.14 and is steady at 5.14v.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

would the backlights stay on if the CCFLS are ok with the main board disconnected or just flash for a split second which is what they are doing with the main board disconnected.

I might have misunderstood, are they staying on or just a flash then off?

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

Just a flash for a split second but i can see they are all coming on.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

when i hit the power BLU_ON goes to 5.16v and drops to 5.14 and is steady at 5.14v.

What does it read before you hit power, which is just standby?

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

BLU_ON reads 0.00 before i hit the power button.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Just a flash for a split second but i can see they are all coming on.

Ok, looks like we're back to powerboard, unhook inverter board/s from powerboard, have cable from powerboard to mainboard in place, see if you have around 400 steady at the filter caps when you hit power, be CAREFUL 400 volts can kill.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

BLU_ON reads 0.00 before i hit the power button.

Ok, that's good.

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

with inverter unplugged and main board plugged in the main filters go to 439 DCV then drops to 147 DCV.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Ok, looks like we have confirmed the problem is on powerboard.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Check the diodes.

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

Any ideal? we have all the low voltage.

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

I have the are all showing good.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

I suspect the little blue cap by the filter caps, think it's CP820 or sum such number.

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

yes, it is CP820 i will change it and let you know.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

One way of testing caps without a cap meter: To test the capacitor with a multimeter, set the meter to read in the high ohms range, somewhere above 10k and 1m ohms. Touch the meter leads to the corresponding leads on the capacitor, red to positive and black to negative. The meter should start at zero and then moving slowly toward infinity.

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

I replaced CP820 and CP804 did no change anything.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Ok, at least it's good to have them off the suspect list.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Thinking it must be in the pfc area, can you check the other components, check anything labeled with second letter P.