Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

[johnboy1313]

I recently picked this set up. When plugged in, the LED on the front illuminates, the startup chime is heard, the backlights come on for ~1 sec, then it all cuts off. I don't see a picture with a flashlight. I haven't connected a source to see if there is sound. One of the troubleshooting steps is to "Check the backlight on, when 30p cable unconnected". With the cable disconnected, the backlight still just briefly comes on before cutting off again. My problem is I don't know if the light is supposed to come on and stay on with the cable disconnected or just flash like it does, so I can't answer YES or NO to the attached troubleshooting chart.

[tom66]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

The light should stay on.

See my video. You may have same issue (I fixed the LE40B652), though my backlight DID stay on when the connector was unplugged, and it turned out to have a bad t-con board.

Common fault on this TV power supply is shorted diode in PFC section causing similar symptoms (no backlight or brief backlight) due to low PFC voltage.

https://www.youtube.com/watch?v=7Xz-iSaEAb8

The smart features on this TV sucked.

[johnboy1313]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Thanks for the quick response Tom. The chime doesn't seem to cut short. I remembered your video and have already attempted powering up with the t-con disconnected. It still does the same thing.

[johnboy1313]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Pictures coming soon.

[tom66]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Check the voltage across one of the large 400V capacitors, both in standby and while powered on (try measuring as power is turned on, see if you get a brief spike or if it stays at one voltage.)

[johnboy1313]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

When plugged in, I have 166.5V at the big caps. At power on, it went up to 390V and held steady. I checked the voltages on the IP board and everything seems correct. At power on, PWR-ON/OFF rose to .9V and held steady. INV_ON/OFF rose to 4.9V and held steady. 5.3V was present as was 13V. I then decided to connect a source and to my surprise, there is sound. At this point, I suspect either the IP board or maybe a bad CCFL.

Short of opening the panel and seeing for myself, is there a way to confirm that the inverter section of the IP board is bad?

IP Board
https://www.shopjimmy.com/samsung-bn...it-rebuild.htm

[johnboy1313]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

IP board schematic

http://www.tgohome.com/ServiceManual...&Search=Submit

[tom66]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Schematic:


You will need to solder wires to the point OVP. OVP is found on pin 10 of UI801 (solder side, secondary; though any component connected to pin 10 should be fine.) It should be low normally.

OVP (over voltage) firing indicates a loose or failed bulb. I don't think it will fire if a transformer is open circuit/high resistance.

DET on pin 5 should also be checked, but I'm not sure what that should measure. I think it's some kind of feedback for regulating the high voltage.

Be careful when removing inverter/power board as damage to tubes is possible.

You can place a solder bridge across CI805/CI806. This disables shutdown timer, so set should start and run continuously. You can then carefully inspect panel on test pattern for bad bulb. Don't run for too long in this condition and shut down TV if burning smell/arcing sound detected.

[johnboy1313]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Schematic:


You will need to solder wires to the point OVP. OVP is found on pin 10 of UI801 (solder side, secondary; though any component connected to pin 10 should be fine.) It should be low normally.

OVP (over voltage) firing indicates a loose or failed bulb. I don't think it will fire if a transformer is open circuit/high resistance.

DET on pin 5 should also be checked, but I'm not sure what that should measure. I think it's some kind of feedback for regulating the high voltage.

Be careful when removing inverter/power board as damage to tubes is possible.

You can place a solder bridge across CI805/CI806. This disables shutdown timer, so set should start and run continuously. You can then carefully inspect panel on test pattern for bad bulb. Don't run for too long in this condition and shut down TV if burning smell/arcing sound detected.

To be clear, I'm just soldering one wire to pin 10 and one to pin 5 so that I have something to probe when the set is powered on?

[tom66]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Yes. The other end you are measuring the voltage against is chassis ground.

[johnboy1313]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Pin 5 jumps to 6.6V when the lights come on but drops out when they shut off.
Pin 10 jumps to 1.99V when the lights come on but drops out when they shut off.

I hear no buzzing or arcing when the lights are on.

[tom66]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Ok. Pin 10 appears to be a fault. Connect pin 10 to chassis ground. Does the backlight stay on?

[johnboy1313]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Ok. Pin 10 appears to be a fault. Connect pin 10 to chassis ground. Does the backlight stay on?

No, with pin 10 connected to ground, they flashed like they have been but there was a loud buzzing coming from the hot side of the IP board then everything cut off. I disconnected it from ground and it is back to the original fault with no buzzing.

[johnboy1313]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

You can place a solder bridge across CI805/CI806. This disables shutdown timer, so set should start and run continuously. You can then carefully inspect panel on test pattern for bad bulb. Don't run for too long in this condition and shut down TV if burning smell/arcing sound detected.

Also, I could be wrong, but aren't CI805 and CI806 already connected at both ends?

[tom66]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Yeah, you only need to bridge one -- they're in parallel. Sorry if I wasn't clear.

[johnboy1313]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

How do I pull up the test pattern on this set?

[tom66]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

The backlight needs to be on -- but you can do it from the service menu.
From standby: Mute 1 8 2 Power on remote. I think it's under "CONTROL".

[johnboy1313]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Jumping CI806 got the backlight on. I need to get the base on and have a look at the screen. I can tell there's a picture but I can't see enough to tell if I've got a bulb out.

[johnboy1313]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Looks like there's at least one bulb out, probably more.

[tom66]

Re: Samsung LN40B630N1FXZA, brief backlight, power up chime, then nothing.

Looks like there's at least one bulb out, probably more.

Looks like only one to me -- though could also be a transformer out.