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Samsung LCD Turns off and on, need help please!! Tried everything

post #1 of 25
Thread Starter 
I am starting a new thread because I have tried everything and search everywhere for help. I have read numerous threads with similiar problems but none helped my issue

I have a Samsung 40' LN40C630K1F. When I turn the TV on, it turns off and on by itself a few times before it finally stays on. After about 10 mintues the tv will start turning off and on every 1 minute or so. I have unplugged the tv over night, next day the same issue occurs.

Here is what I have tried:
tried different hdmi cable
tried different power cord
plugged tv directly into the wall
removed batteries from remote
bypassed cable box
cleaned touch senstive buttons on front of display
remove back panel and checked for bulging or bad capcatiros on power supply board, none were bad
replaced power supply board anyway (problem still occured)
disconnected two cables from power supply board to which I think is the backlight inverter board. when I turned the tv on, no picture appeared but the tv still turned off and on by itself.

I ran out of options to try. Hopefully someone out there had suggestions or ideas on what else I can try.
I am not calling a repair man yet.

Thank you
post #2 of 25
Based on the theory of operation.

Part of the power supply is always on (24/7) and and supplies 5vdc to power the Processor and the Infrared remote receiver module (e.g. waiting for the for a 'on' command from the remote control or from the power switch).

Because it's always on, the eProm on the main board, can become corrupted by voltage spikes and surges. You have already unplugged the set over night, which should have restored the program to factory settings.

When the power on command is received, the processor on the main board, will send a turn on signal (e.g. typically 3.3~5vdc) to the power supply module, which turns on the entire power supply.

However, since you have already replaced the power supply board, most likely it was not the problem.

It seems that the turn on signal from the main board is intermittent (e.g. caused by faulty component, cold solder connection etc.). One simple thing to try would be reseating (cleaning) the connector.

I have the same TV and love the PQ.

However, while the next step would be to replace the main board, they are not cheap and while likely the problem, not guaranteed to fix.
post #3 of 25
Thread Starter 
Thiao...thank you for the great information.

What main board are you talking about? Is it the main board with all the av connectors? Hdmi etc? I will try reseating and clean those cables that connect to the ps board
post #4 of 25
Thread Starter 
I disconnected/reconnected cable from ps board to the main component board and clean the connectors, the tv still was turning off and on by itself. It finally stayed on for about 5 mins then turned off and on again.
Is it the main board that needs to be replaced?
I looked at the main board closely and do not see anything wrong with it.

Any other suggestions?
post #5 of 25
While it was a long shot, about all you could do to clean the contacts would be, using a Q tip and Isopropyl alcohol, to carefully wipe the 'male' pins.

Yes, the main board is the one with all the A/V connectors.

At this time; it is suspect and the next logical step, since you did the factory reset and replaced power supply board, as it supplies the signal to turn on the full power supply, that is necessary for the set to operate.

If it were me, using a multimeter, I would monitor and verify that the main board is sending the correct power supply turn on level, all the time. However, this is probably beyond the scope of most DIY .

Alternatively, here are some examples of some replacement 'main' boards for your TV.




Please be sure to verify the correct part number prior to purchase.
post #6 of 25
Thread Starter 
The part number for the main board I have is "BN94-02701F". I can not find this board anywhere in stock. There are compatible boards but I don't know if I should try one of them or not.
Any thoughts?
post #7 of 25
The shopjimmy link has a video explaining the compatibility of board part numbers.

However, it does not explain the significance of the last letter.

The last letter is the board revision level. Revisions are made over time for a variety of reasons. In this way, the company keeps their manufacturing processes up to date. Typically most are minor changes, such as the factory it was made in, change and/or addition of a component manufacturer source etc. Occasionally, service manuals include a table of revisions.

Again, after the steps you have already taken, the main board would be suspect (e.g. not supplying a consistent turn on signal to fully turn on the entire power supply).

I don't have the service manual for this particular set, but my guess is that pin 2, labeled SW PWR, on connector CN201, provides the turn level required to turn on the entire power supply.

If you have a multimeter, it should real 0 to .8 volts for off and 3 to 5 volts for on.

While I'm not suggesting you do this (e.g. requires skill and care not to accidentally short and damage other circuits), tracking the turn on level vs when the TV operating correctly, would be helpful in diagnosing the problem.

BTW, I noticed that retechtv has a no charge board return policy, as does shopjimmy (which specifies for technicians).

Perhaps a call to either would further clarify the revision level and return policy.
post #8 of 25
this is sounding like the scrambled eeprom, or the bad transistor solder joints.

try finding loose transistor solders, then hunt down the eeprom and service threads

post #9 of 25
Looked at that link.

Although the OP symptoms are similar, that thread covers older production models, made from 2006 - 2008 (last affected Samsung models were LNxxAxxxx models). Back then, counterfeit electrolytic capacitors, that prematurely failed, worked their way into the production lines at Samsung, as well as many other manufactures (e.g. Apple, Sony etc.). Samsung has adopted a policy of repairing products affected, at no charge.

The OP set is a 2010 model and he has already replaced the power supply board, where those faulty capacitors were mainly used.

Note to OP: Just a sanity check.......usually the bad capacitor issue symptoms begin slowly and progresses over time, to where the set will not turn/stay on at all.

A corrupted eProm could also be the problem however, the set was unplugged for some time, which should have restored the factory default settings.

Post #7 in that thread suggests going into the service menu and attempting to repair the eProm. It's not clear this is a sound methodology and far to many folks have 'bricked' their sets by fiddling around in the service menu.

I would not dismiss a cold solder joint being the problem. However, which one among so many possibilities (e.g. upward of 500).

Note to OP: Did you also clean the connector pins on the power supply as well?
post #10 of 25
Thread Starter 
I did clean the connectors to the power supply as well

I just ordered BN94-02701T from retechtv, hopefully the board is the same. They are the only company who had a board for this model Samsung. Everyone was sold out.
It says its compatible with this tv model, but we will see. If the board is the not answer, I don't know what else I am going to do. Everyone has given great advice and suggestions, so lets hope replacing the board does it.

I will keep you posted smile.gif
post #11 of 25
Thread Starter 
I installed the new board today, the board is receiving power but the tv does not even turn on now. The power light on the tv blinks five or six times when I plug the power cord in but no power sound from the tv.
What is going on?
The board I bought is compatible with this tv.
post #12 of 25
Thread Starter 
The front touch sensor buttons now do not work either with this new board
post #13 of 25
While I don't have the service manual for your specific TV, below is the 'no power' troubleshooting procedure for a very similar Samsung set (ignore the indicated part numbers).

Also, SMPS (switched mode power supply) and IP are just alternative ways of saying power board (SMPS relay = IP relay = the relay on the power board).

Basically, pretty much everything points to replacing either the power or main board (hopefully both of the replacement boards were good).

From you last notes, for some reason, after replacing the main board, all the required voltages are not operational (e.g. main board still not turning on the full power supply, faulty power board etc.).

Clicking on picture to enlarge.

post #14 of 25
Thread Starter 
I contacted the co about the board problem and they are telling me the board is not compatiable with the tv, whère numerous sites say BN94-02701T is a compatiable board to BN94-02701F.
This is annoying.
So its best if I hunt for BN94-02701F, which I cant find
post #15 of 25
You might call Shopjimmy.......their getting board inventory all the time.

BTW, they show that they have (4) available repair parts kits (e.g. power, main, TCON, Inverter) in stock for the LN40C630K1F for $130, which include the BN94-02701F Main Board.

post #16 of 25
Thread Starter 
thiao...Thank you for finding that kit, I just placed the order so I will keep you posted.

Thank you for all knowledge on this tv model.
post #17 of 25

plenty of information on you tube. Common problem with many Samsung tvs
post #18 of 25
Thread Starter 

The replacement "BN94-02701F Main Board" was the problem. I replaced it and the tv has been working fine since I replaced the board.

post #19 of 25
Hi Dave,


I have the same set and it was definitely worth repairing (especially on a DIY basis).

BTW, since providing the trouble shooting chart in post #13, I found and downloaded the service manual for this TV.

If you would like a copy, PM me and I'll let you know where you can down load a free copy as well.

Edited by thiao - 12/10/12 at 11:56am
post #20 of 25
Great information here. I have an eerily similar issue and have also tried the power supply replacement to no avail. I will now attempt to replace the main board based on this thread. Thanks guys.
post #21 of 25
I have the same Samsung LN40C6301FXZA my tv wasn't blinking or clicking on and off..the power light was solid light up. it wouldn't turn on whether touching the panel or with the remote. I was reading about the capacitors going bad and causing the problem. I took the cover off and checked the power supply panel looking for the capacitors but they all looked good not one looked bad. so today I ordered the power supply panel. then i found this thread. the OP did the same thing ordered the power panel and it didn't fix the problem. i started checking the ribbons cables. plugged tv back on the outlet. the power led came on solid but didn't come on...i then took the cable ribbon from the main board to the power supply panel , when i did that the tv panel light up. the red light power on front was off but the tv was on. i had no control over the tv doing anything it was just light up. plugged back the cable ribbon from the main board to power panel . the tv turned off again..now i'm thinking its the main board panel its bad..i think i will order a new main board panel and plug that in first, and if it works i will send back the power supply panel. i will let you know what happens..biggrin.gif
post #22 of 25
word of advice, even it if seems to be fixed upon any replacements to power supply or main board (or any other part), give it a good month of no issues before you render the problem solved. just saying because when i tried changing the power supply, my issue stopped for 2 weeks or so and then started back up again much to my chagrin.
post #23 of 25
UpDate... it was the main board panel. i had to order a brand new one from Samsung. i installed it in and when i powered up , it went to the setup menu . setup everything again clock setup, zone region etc... its been 3 weeks now and everything is working fine..i hope this helps anyone...
post #24 of 25
Glad to hear your problem was resolved.
post #25 of 25
Originally Posted by morganim View Post

this is sounding like the scrambled eeprom, or the bad transistor solder joints.

try finding loose transistor solders, then hunt down the eeprom and service threadsEoRNcT



 Try unplug the LVDS cable from the Tcon (the board in the top or bottom middle of the set with one cable going to the main) and try your power button. In this case i doubt it will work, but you should try first. If you get power on and backlight, Tcon is bad. If the problem persists, check power supply voltages from main harness between SMPS and Main board. 

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