Samsung Model TV LN40B630N1 No Picture

[cfuller201]

New Member. First Request for info
TV Symptoms: When plugged into 120 V AC, front panel power on light is solid red. No picture, no sound, no backlight, lcd panel is black. When I unplug cable to Main board (BN41-01149A) from PSU/Inverter (BN44-00264A) backlight comes on completely and all voltages I measured are present. So my guess is there is a problem with Main PCB or TCON.

Question: How to troubleshoot which one to replace. 2 years ago I replaced the TCON board.

Samsung Model: LN40B630N1F
Model Code: LN40B630N1FXA
Manufactured: 2009
3 Circuit boards
- BN41-00264A Power Supply Board (Recently repaired at Modus PTS, symptom was no dc voltages present on connector (CNM802) to main board. Now all voltages are present.
- BN41-01149A Main Board
- BN81-02352A TCON board

DC Voltages present with Main PCB cable (CNM802) disconnected from Power supply, TV plugged into 120V AC, backlight fully on.
(? not measured, see below)

1 PWR-ON/OFF ? Actual
2 H_Sync ? Actual
3 STBY 5.3V 5.22 Actual
4 GND OK
5 GND OK
6 GND OK
7 13V (S) 13.0 V Actual
8 13V (S) 13.0 V Actual
9 GND OK
10 GND OK
11 GND OK
12 GND OK
13 5.3V 5.22 Actual
14 5.3V 5.22 Actual
15 5.3V 5.22 Actual
16 5.3V 5.22 Actual
17 GND OK
18 GND OK
19 13V (M) 13.0 V Actual
20 GND OK
21 13V (M) 13.0 V Actual
22 13V (M) 13.0 V Actual
23 Inv_ON/OFF ? Actual
24 N.C. (Not Connected
25 E-PWM ? Actual
26 GND OK
27 DET_5V 5.08 Actual
28 N.C. (Not Connected
29 N.C. (No Connected
30 N.C. (Not Connected

[tom66]

Re: Samsung Model TV LN40B630N1 No Picture

Did you turn off the melody in the service menu?

If not do you hear a melody when turning the set on -without- the T-con connected?

[cfuller201]

Re: Samsung Model TV LN40B630N1 No Picture

No and NO

[tom66]

Re: Samsung Model TV LN40B630N1 No Picture

Sorry I meant melody in the user menu, but regardless you previously heard a melody, but now you do not?

In which case, the fault is pretty much guaranteed to be on the main board. You have replaced the T-con and the power supply has been repaired too? These are not very reliable TVs... I have only done one but I could see they are built down to a low price.

[cfuller201]

Re: Samsung Model TV LN40B630N1 No Picture

The TV went out during a heavy rain/lightning storm. BTW I have a Masters of Electrical Engineering from the University of Florida. For $50 a tech will diagnose problem but typically replacement boards are very hard to find. We have 8 LCD TVs in the household so I want to get better at fixing.

[tom66]

Re: Samsung Model TV LN40B630N1 No Picture

I often hear "heavy rain/lightning", but we only find that around ~10% of the time that is actually the case. I have only seen some few examples of direct surge damage. Most of the time it's a coincidence or bad luck...

[efan]

Re: Samsung Model TV LN40B630N1 No Picture

Have you tried reset the eprom. It work for model LNS4051. following is from other forum:
Short out the eeprom pins 5 & 6 .The easiest way is to carefully solder a thin wire (about 6" length) to each of the 2 little round pre-soldered pads that lie in front of pins 5 and 6 and use the wires as a contact breaker to easily shorten the pins. 2. Turn on the power - Instead of the usual noticeable relay click, you get a faint click, the backlight stays off, nothing else happens. 3. Wait around 1-2 secs ( anything longer than this NEVER seemed to work ). 4. Remove the short. Note: by now the TV is already in normal standby operation, but EEPROM values are still bugged. 5. Press the service mode key combination on the remote control. Note: check service manual for the correct combination or try the following: * info, menu, mute, power on) - In that order individually, one at a time. * mute, 1, 8, 2, power on) - In that order individually, one at a time. 6. TV should come on with noise picture and then the service menu (press Source if it is difficult to read) 7. Immediately go to option Adjust and turn OFF the watchdogs (especially in case your TV keeps turning off by itself at this point) 8. Now, for EVERY OPTION in ALL THE SUBMENUS, change EVERY VALUE and then change it back (toggle right-left) to assure the EEPROM data is re-written correctly

[cfuller201]

Re: Samsung Model TV LN40B630N1 No Picture

Thank you. I will put back together and try this.
In the meantime, can someone tell me which of these signals on the power supply connector comes from the main board to light up the video. Pin 23 inv_on/off seems like a good candidate. That is when I disconnect the psu connector I get the backlight screen lit up. Thoughts"

[tom66]

Re: Samsung Model TV LN40B630N1 No Picture

The INV ON/OFF has a resistor to pull it up on the power board. This makes the inverter signal high when the connector is disconnected. The main board normally "pulls down" the signal, and releases it (letting it go high) when the backlight needs to come on.

[cfuller201]

Re: Samsung Model TV LN40B630N1 No Picture

ModusLink PTS repaired the PSU/Inverter board. They suggested I send back the PSU and Main board for testing and Repair. I UPS'd to them today. Couldn't find any schematic on the Main logic board. Think Problem is with the INV ON/Off Pin from the main board. I'll let you know what happens.

[cfuller201]

Re: Samsung Model TV LN40B630N1 No Picture

When I get these 2 boards back, can I power up without the tcon board. What would I get on the screen? Thanks. Or should I put all boards back in and power up?

[tom66]

Re: Samsung Model TV LN40B630N1 No Picture

You should see a backlit but blank screen without t-con. It may go white or black.

[cfuller201]

Re: Samsung Model TV LN40B630N1 No Picture

Received Main board back from repair and installed. Display is perfect before I fixed the power supply board and main board.
Final report. Thanks for your inputs.

[cfuller201]

Re: Samsung Model TV LN40B630N1 No Picture

Display is now perfect.

[budm]

Re: Samsung Model TV LN40B630N1 No Picture

Great news, so how did they charge you for the board repair?

[cfuller201]

Re: Samsung Model TV LN40B630N1 No Picture

$80 (incl shipping for the PSU/Inverter and $112 plus $29 shipping for the main board. I felt like I got hit by a lightning surge. 2 years ago I replaced the TCON board. Doesn't say much for Samsung reliability. They have a 6 month warranty on the board repair where they pay the shipping both ways. Moduslink PTS in Bloomington, In. Turnaround was less than a week each time.
Pros: Board were repaired professionally. TV now works.
Cons:
- First time with PSU, not repaired (No voltages out)
- Sent back PSU with RMA, repair was done at no charge.
- Then Main board showed up as failure when PSU installed, Sent back with PSU and Main board and they repaired and tested together. Returned in a box 2 times too big which cost $28 shipping rather than $12 by UPS.
- Communication is only by email to customer service. Once you send in the board there is no contact until they call for payment. I would have preferred to talk to a "human".
- Last, I asked to be told what they replaced. They refused.

Overall: Very satisfied and I learned a lot about how to repair in the future. We have 8 LCD TVs in our household. This forum was very helpful to me in getting to the bad board.