Need help with Samsung LN40E550f7f

[Kindred1]

Re: Need help with Samsung LN40E550f7f

Bottom line is we do have voltage from main to power board when t.v. is powered on. - Sorry for the confusion.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Looks like the mainboard isn't sending the blu_on signal to the power supply.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

You could try fixing the mainboard but it can be very technical.

[Kindred1]

Re: Need help with Samsung LN40E550f7f

So to clarify on my end. there is no power on Blu_on - during standby. When tv is powered on, then I have voltage. Therefore, the main board is sending signal and the signal is staying on. - So, I think I'm back to checking the inverter board. The layout is different than the ones I find online. I'm going to look again, the post a pic of it if I'm unsuccessful. Unless you all have any other has suggestions.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Bottom line is we do have voltage from main to power board when t.v. is powered on. - Sorry for the confusion.

Ok, just to be clear, with all boards hooked up, you do have about 3 volts on blu_on pin, when you check it?

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Well if your inverters you have 2, the original and one you bought, check out ok, it may be a backlight issue.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

http://www.shopjimmy.com/cmo-27-d070...t-inverter.htm good pic. of the inverter, probably test it next.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

https://www.youtube.com/watch?v=oE6K4xBVweA checking inverter its a samsung but a different model, gives you a good idea of what to do.

[freakaftr8]

Re: Need help with Samsung LN40E550f7f

This model does have pull up resistors. Point in case, if you unplug mainboard from power supply you will get backlights. If you don't, look at inverter or CCFLs.

Shine a flashlight into the screen and hit the menu button. See anything?

These E series were some if the last that used CCFLs before going all LED. They have a moderately high failure rate. The connections that the CCFL bulbs use inside are spring loaded into the sockets. They break down.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Was trying to find a video with someone testing an E series inverter but no luck, not sure of the differences between series.

[budm]

Re: Need help with Samsung LN40E550f7f

This power supply board it supplies high frequency AC to connector CNI801 pin 3 (LOW 193VAC) and pin 1 (HIGH 373VAC) of the power supply board to drive the Primary winding of the Inveter transformers on the Inverter transformer board.
If it is bad lamp problem, the backlights should flash on for seconds (unless ALL the lamps are bad which is not likely) before the inverter transformer driver circuit on the power supply board goes into protection shutdown.
O.P. need to verify if he is getting the high frequency AC drive Voltage to drive the primary side of the inverter transformer on the inverter transformer board or not.

[Kindred1]

Re: Need help with Samsung LN40E550f7f

Ok, just to be clear, with all boards hooked up, you do have about 3 volts on blu_on pin, when you check it?

With everything hooked up and the tv powered on I get 5.14v on blu_on.

[Kindred1]

Re: Need help with Samsung LN40E550f7f

This model does have pull up resistors. Point in case, if you unplug mainboard from power supply you will get backlights. If you don't, look at inverter or CCFLs.

Shine a flashlight into the screen and hit the menu button. See anything?

These E series were some if the last that used CCFLs before going all LED. They have a moderately high failure rate. The connections that the CCFL bulbs use inside are spring loaded into the sockets. They break down.

Yes, I can see the screen static and some lettering with the flashlight. No backlights with mainboard unplugged.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

I guess test the inverter, if that's ok, what else could it be but a bad ccfl?

[Kindred1]

Re: Need help with Samsung LN40E550f7f

This power supply board it supplies high frequency AC to connector CNI801 pin 3 (LOW 193VAC) and pin 1 (HIGH 373VAC) of the power supply board to drive the Primary winding of the Inveter transformers on the Inverter transformer board.
If it is bad lamp problem, the backlights should flash on for seconds (unless ALL the lamps are bad which is not likely) before the inverter transformer driver circuit on the power supply board goes into protection shutdown.
O.P. need to verify if he is getting the high frequency AC drive Voltage to drive the primary side of the inverter transformer on the inverter transformer board or not.

I think we found our problem Budm. I am not getting voltage at those pins. I am checking with inverter unplugged direct from the pins on the board.

[Kindred1]

Re: Need help with Samsung LN40E550f7f

So, where do I check for the fault?

[Kindred1]

Re: Need help with Samsung LN40E550f7f

Weird thing is, I remember getting some voltage there early on, tho' I don't remember what they were.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Trying to remember if you had the proper voltage on the filter capacitor legs?

[Kindred1]

Re: Need help with Samsung LN40E550f7f

That's the large 450v caps?

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Yes, remember high voltage in that area use caution.