Need help with Samsung LN40E550f7f

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

voltage as follows
with all boards connected and TV on, but no backlights.

psb:
1. B13V----12.88v

2. DIM----2.77v

3. B13V----12.87V

4. NC -0V

5. B13V----12.87v

6.BLU_ON---5.14

7. B13V---5.14v

8., 9., 10 GND- 0V

11.B5V---5.17V

12 A5V---5.18V

13. B5V---5.17V

14. PS_ON---3.30V

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

correction

BLU_on---5.14v

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

recheck 7, looks like it should be 13.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Guess we need to figure out why 7 is only 5 volts.

[Diah]

Re: Need help with Samsung LN40E550f7f

you disconnect the MB from PWB the led back light blinked for second or less.. you have bad back light... take screen apart and keep the MB disconnected to repair the LED back light until they all on and stay on.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Unplug inverter/s from powerboard, (best practice is always unplug tv from outlet before unplug any cables etc. then plug tv back in outlet and try it) see if 7 comes up to 13 volts.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

If powerboard isn't fully working there's no need to go further until it works correctly.

[budm]

Re: Need help with Samsung LN40E550f7f

1) Pin 7 is more likely to be OP measurement notes error.
2) This TV does not have LED backights, it has CCFL
https://www.badcaps.net/forum/attach...8&d=1519166063
3) You need to check the DCV between the two legs of the main filter cap to see if you have PFC Boosted Voltage of 380 ~ 400VDC or not for the inverter Transformer drive circuit to work.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

1) Pin 7 is more likely to be OP measurement notes error.
2) This TV does not have LED backights, it has CCFL
https://www.badcaps.net/forum/attach...8&d=1519166063
3) You need to check the DCV between the two legs of the main filter cap to see if you have PFC Boosted Voltage of 380 ~ 400VDC or not for the inverter Transformer drive circuit to work.

He did, post 160.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Check the little blue capacitor by the filter caps labeled CPxxx something like that. Did you heat the powerboard with a hairdryer?

[budm]

Re: Need help with Samsung LN40E550f7f

nomoresonys,

The main filters comes up to 415 DCV for a split second the settles down to 159 DCV.
CP804 looks good but i know that don't mean nothing.
Do i need to remove it and check it?

Sounds like the PFC Boosted Voltage did kick on but went up over 400V so it may have trigger PFC shutdown so the Voltage goes back down to 160V.

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

with main board disconnected the backlights flash for a second and all of them come on and are white, no black ends on the CCFL's buy the way i have 5.14 on BLU_ON with main board connected.

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

nomoresonys

Heating the power board makes no change.

[pocketwatch62]

Re: Need help with Samsung LN40E550f7f

Sorry pin 7 B13V reads 12.87 DVC.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

with main board disconnected the backlights flash for a second and all of them come on and are white, no black ends on the CCFL's buy the way i have 5.14 on BLU_ON with main board connected.

If backlights come on and stay on, then usually it points to a problem with mainboard, sometimes panel or tcon.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Sorry pin 7 B13V reads 12.87 DVC.

Thought it was, would be pretty strange to only be missing one 13.

[R_J]

Re: Need help with Samsung LN40E550f7f

.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Might be a dirty or oxidized connection, try unlug n replug the cable from powerboard to mainboard on both ends a few times, carefully just want to make sure there's good contact.

[pocketwatch62]

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.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Test the bl-on pin again, see if it changes voltages when you hit power.