Samsung LN46C600 LCD TV - No Picture but Sound

[rba333]

Hey all...new to this forum and would appreciate any help. So I'm watching TV the other day and all of a sudden the screen goes black but the sound still works. I turn it off and on, unplug and plug back it, all the usuals and it still is doing the same thing. After a while, the screen start flickering "rays of light". It seems like it does it in a pretty consistent pattern every few seconds. It starts after the TV has been on for about 20-30 seconds. I've had the TV for about 2 years so it is out of warranty, but it was unplugged for about a year b/c I wasn't using it. I've attached two pictures of the "rays of light". Any help would be awesome!

[capkid]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

Have you tried leaving it off for a while (e.g. 1/2 hour) to see if your picture returns (not saying that this is a fix, but it might help determine if you have an internal thermal issue).

[rba333]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

Yes, I left the TV unplugged for 24 hours and tried it again. Same condition.

[capkid]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

Unless someone else has seen this issue and has a quick resolution (good or bad), it might be time to open it up or take it to a shop.

Edit: I'm not sure if this "fix" is appropriate for your TV, but I'd check for other issues on the circuit boards first (e.g. bad capacitors):

https://www.badcaps.net/forum/showth...amsung+flicker

http://www.youtube.com/watch?v=1ZwQ0gRQ9sg

[rba333]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

Went through this and cut the "JP852". Powered back on and still broke.

[rba333]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

Pictures of the board uploaded. If anyone needs another angle/photo let me know.

[capkid]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

A pic of the whole chassis might be helpful. Here's the schematic for the power supply (PSU) if you need it:



I'd start by checking PSU output voltages at the connectors to the main board and backlight inverter(s).

[rba333]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

Chassis attached

I don't own a multimeter so this may be the end of what I can do unless someone has another idea?

[capkid]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

Chassis attached

I don't own a multimeter so this may be the end of what I can do unless someone has another idea?

I was referring to the whole back of the TV when I mentioned "chassis", but I'm fairly familiar with the layout. Others that wish to contribute may need a pic, though. A relatively inexpensive multimeter might suffice. Otherwise, you're left with a shotgun approach of replacing circuit boards.

[rba333]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

Just spoke with Samsung customer support and they are recommending a tech comes out to look at it. No surprise there but they didn't offer any insight either.

[capkid]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

Just spoke with Samsung customer support and they are recommending a tech comes out to look at it. No surprise there but they didn't offer any insight either.

Once a TV is out of warranty, calling customer support is usually a waste of time (some may say that's true when a TV's under warranty, also).

Here's a repair service on eBay for the PSU if you choose to take the shotgun approach. I've personally never used this company. Also, if you decide to go this route, I'd mention to them that you already cut the jumper before you purchase their service: http://www.ebay.com/itm/Samsung-BN44...item4174a2edc6

[tom66]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

$59 for cutting JP852/854??? Rip-off. For flickering backlight only.

[capkid]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

$59 for cutting JP852/854??? Rip-off. For flickering backlight only.

Yeah, I laughed when I first saw that ad. Unless there's a secondary fix for PSUs not cured by cutting the jumper, that's ridiculous.

[tom66]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

I figured out that JP852 disables the PFC UVLO on the backlight circuit (it cuts the signal from opto PCI801S), which isn't a big deal but will cause problems on low AC voltage or if the PFC circuit fails. It's basically an AC detect. It seems the AC detect type circuits are very prone to failure, I wonder if it's due to the sensitive circuitry (input voltage comparator) being damaged by high voltage transients (>1kV) that make themselves past the divider resistors. I can count on two hands the number of LG plasmas with AC detect issues I've seen on here, so it's not super common but it's definitely a fairly typical problem.

[ben7]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

I figured out that JP852 disables the PFC UVLO on the backlight circuit (it cuts the signal from opto PCI801S), which isn't a big deal but will cause problems on low AC voltage or if the PFC circuit fails. It's basically an AC detect. It seems the AC detect type circuits are very prone to failure, I wonder if it's due to the sensitive circuitry (input voltage comparator) being damaged by high voltage transients (>1kV) that make themselves past the divider resistors. I can count on two hands the number of LG plasmas with AC detect issues I've seen on here, so it's not super common but it's definitely a fairly typical problem.

Yeah ... I bet it is from spikes too. I wonder if zener diode(s), across the comparators' inputs to ground, would prevent this problem.

[tom66]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

It wouldn't. Zeners are too leaky (more than microamps) and their inductance and capacitance is too high. The correct solution is to detect the failure of one of the local supplies like the 12V or 5V.

[rba333]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

A pic of the whole chassis might be helpful. Here's the schematic for the power supply (PSU) if you need it:



I'd start by checking PSU output voltages at the connectors to the main board and backlight inverter(s).

Sorry for the hold up but I was able to get to the store and purchase a multimeter. Forgive me for my lack of knowledge but I have no idea where I should be looking for the connectors. I've attached a picture of the full chassis this time.

[tom66]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

We require a closer picture of the connector between the power board and main board. Also, a picture of your multimeter could be helpful, if you are new to using one.

[capkid]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

Here are some pics of the boards.

[rba333]

Re: Samsung LN46C600 LCD TV - No Picture but Sound

Here is a link to the multimeter I purchased: http://www.harborfreight.com/7-funct...ter-98025.html

If you need other pics besides the one capkid posted I can provide.