Samsung LN40E550

[stonoguy]

My mother's HDTV got hit by a power surge during a thunderstorm. The symptom of the set is that it plays fine for about 4 to 5 minutes then cuts off. Stays off (no sound or pix) then after about a minute or so, the set cuts back on and plays fine...then repeats the on/off scenario over and over. The TV is 3+ hours away...Was trying to get a grasp on what to check first. I worked on TVs for over 20 years when they had CRTs and flyback transformers. I have replaced capacitors and a shorted diode in a few of my LCD/LED sets, as well. Any thoughts? Point me in the correct if this isn't the right forum in which to post! Thanks!!

[stonoguy]

Re: Samsung LN40E550

I have more info....printed on the owners manual is 'SERIES 5 550'.
Sounds as if a componet on the power supply board is heating up, shutting
the set down, cooling off & the set returns to the ON mode. Am I off base
here or should I wait until I get the set n front of me??

[CapLeaker]

Re: Samsung LN40E550

Not much you can do until you have the TV in front of you. Then you have to figure out is it the Main board causing this (losing PSon voltage to the PSU), or the PSU itself.

[stonoguy]

Re: Samsung LN40E550

I have FINALLY gotten the TV. The set played for about 30 minutes. I turned the set off to remove the probe I had attached to the HOT ground and went to turn on the set, it would not turn on. The set can only be controlled from the remote. Luckily, I have a Samsung TV that this remote will control. I checked the usual...fuses and such....no luck. It appears that this set has a BN44-00440b power supply board in it. I can not find the correct schematic. The one I do have, the components' ID on the board do not match the components' ID on the schematic....making it difficult for correctly IDing the components. Will someone point me in the correct direction for troubleshooting this set? I surmise there is no voltage going to the standby. If any pics need to be accessed, I will be more than happy to do that! Sets that can only be operated by the remote are, IMHO, a PITA!

[freakaftr8]

Re: Samsung LN40E550

As you mentioned the TV only works via remote. The touch sensitive buttons on the front of the TV panel may be at fault try powering up the TV and well its on, unplug the front touch sensitive buttons from the main board. See if the TV turns off after 5 minutes then..

I should note I have seen these touch sensitive buttons fail before also I have seen a corrupt EEPROM cause this issue as well

[stonoguy]

Re: Samsung LN40E550

I have done as suggested....no luck. I wasn't aware there were touch sensitive buttons on this model. BTW, where is the IR pick-up? Maybe someone can point me to the right place to get a schematic for this set? I haven't found one. Used to be able to get just about any make/model from Sams.

[budm]

Re: Samsung LN40E550

http://www.shopjimmy.com/samsung-bn9...-ir-sensor.htm

P-Touch and IR are on the same board.

[stonoguy]

Re: Samsung LN40E550

Thanks for the info! When troubleshooting a dead condition, can the boards be removed from the set and worked on? This set has 4 boards (that I can see, anyway). Power supply board, a PCB that contains 2 HDMI inputs, ANT input, composite & audio inputs and output to the 2 speakers, a board that supplies voltage to back light LCDs, and a board that connects the touch sensitive buttons & IR. If this is the case, it sure would save a bunch of area!! I would really like a schematic for this chassis...any idea where I can access one??..........Sure would make things simpler!!

[stonoguy]

Re: Samsung LN40E550

I believe I have acquired a schematic....what voltages are supposed to be present? I had ~400 volts on the 2 filter caps when the set was playing....now that the set is dead, the voltage is ~ 168 volts.

[budm]

Re: Samsung LN40E550

I believe I have acquired a schematic....what voltages are supposed to be present? I had ~400 volts on the 2 filter caps when the set was playing....now that the set is dead, the voltage is ~ 168 volts.

OK , when the set is dead, check and see if you still have standby Voltage, if it does, see if you have PS-ON signal.

[stonoguy]

Re: Samsung LN40E550

I am going to have to take a break from repairing this set. as I am helping out friends who were effected (big time) by all the rain we had over the past couple of days...... I live in SC.....thanks to all who have guided me thru this so far. When I get back to "normal mode". I'll try (hopefully successfully) this one more time. Again. thanks! See y'all soon!

[freakaftr8]

Re: Samsung LN40E550

Wish you all the best. I've seen the news and what happened there. Just horrible.

[stonoguy]

Re: Samsung LN40E550

Finally, I am able to dedicate some time to try and repair this set. After helping friends, holiday activities, etc…..

I have been able to piddling around with it some. I believe, too, that the schematic I have isn't jiving with the components I have on this BN440-0440B board. I have searched for the stby 5.3v rectifier (DM857) but have yet to find it. I guess I'm used to Sams Photofacts…..”spoiled”.

Anyway, I didn't find the 5.3 stby volts. I measured for this voltage at the cable that runs from the power supply board to the board where the IR pick-up is located. All the fuses are OK. 120V AC is there. I have ~165v DC on the 2 filter capacitors (100uf @ 450v) as related to HOT ground. That's where I stand now. Any photos that are need can be supplied.

[budm]

Re: Samsung LN40E550

Please upload good clear straight shot of the top and bottom sides of the board.

[vinceroger69]

Re: Samsung LN40E550

i think the board number above is a missing a number? maybe its a BN44-00440B.

[stonoguy]

Re: Samsung LN40E550

You are correct!

[stonoguy]

Re: Samsung LN40E550

Here are photos...if not adequate, please advise......Thanks!

[budm]

Re: Samsung LN40E550

OK, What DCV do you have on connector CN802, make sure to put pin number, follow by pin name, and follow by the DCV reading for each pin.
Pictures provided by shopjimmy.

[stonoguy]

Re: Samsung LN40E550

OK….here are the readings…...looks as if the 13v & 5v are low or non-existent.

Pin # Pin Name DC readine

1 B13V 2.3v ~ 1.9v
2 P_DM (DIM?) 0.25V ~ 0.15V
3 B13V 2.3V ~ 1.8V
4 N/C
5 B13V 2.3V ~ 1.8V
6 BLU_0N .23V ~ .03V
7 B13V 2.3V ~ 1.9V
8 GROUND
9 GROUND
10 GROUND
11 B5V .28V ~ .05V
12 A5V ~ 1.0V
13 B5V .28V ~ .05V
14 PS_ON ~ .69V

[budm]

Re: Samsung LN40E550

You have to have the connectors in place (boards connected) then make the DCV measurement, it will not be easy, you will need skinny probe.