Samsung LE32B450C4W smoking ccfl xfrm

[notallbad]

Samsung
LE32B450C4WXXU

Power / Inverter board : BN44-00261B

TV received with a dark band across the top, picture fine - backlight issue.

Tested ccfl xfrm and replaced after finding differences between the 2 on the board.

Replaced transformer QGAH02094 NY0903FB with QGAH02094 0 11TM49 A.

Had it on for an hour and had a burning smell, thought it was burning off lacquer from the new xfrm, but now when turning tv on it smokes and almost immediately after turning on.

Could just be a dodgy xfrm, ebay seller immediately refunded, no questions or fuss, did advise could be fault on board causing this.

Anyone had any experience with these xfms?


On inspection found the HV output side burning/smoking and the resistance is way high,

[notallbad]

Re: Samsung LE32B450C4W smoking ccfl xfrm

Photos to follow along with a few quick tests.

[notallbad]

Re: Samsung LE32B450C4W smoking ccfl xfrm

So driving the top ccfl lamps with the 'good' xfrm, moved psu/inverter board up so the bottom xfrn is connected to the top lamps, the lamps come on briefly, 2 secs to black obviously as the other xfrm is not connected to anything, no flickering like is does with the 'bad' xfmr and no smoking/burning.

I think this test is good enough to eliminate the lamps/wiring.

As a note, when connecting the 'bad' xfmr to the bottom lamps the xfmr still smokes/burns.

[tom66]

Re: Samsung LE32B450C4W smoking ccfl xfrm

That would be a reasonable elimination.

How about a picture of the power board?

Maybe the transformers are different parts? Check schematic, if available, to be sure.

Are they driven from the same power electronics (transistors, etc) and is it a 24V inverter or high voltage (primary side powered, danger of electric shock etc.)

[notallbad]

Re: Samsung LE32B450C4W smoking ccfl xfrm

Photos

[notallbad]

Re: Samsung LE32B450C4W smoking ccfl xfrm

On COLD side of xfrm QGAH02092 SW , so must be driven by 24v.

[tom66]

Re: Samsung LE32B450C4W smoking ccfl xfrm

It appears to use a transformer to drive the transformers. TI9015. That creates the pri-sec isolation. Not a 24V design though.

[notallbad]

Re: Samsung LE32B450C4W smoking ccfl xfrm

Isn't that TI801S?

[tom66]

Re: Samsung LE32B450C4W smoking ccfl xfrm

Yes... probably... hard to read in your photo

[budm]

Re: Samsung LE32B450C4W smoking ccfl xfrm

I ran into two of these setups and the lamps were bad, it has blackened ends (you can see red glow at the ends inside the lamps) and draw lots of current even though the lamps still light up. I would inspect the lamps real well also.

[Shinju]

Re: Samsung LE32B450C4W smoking ccfl xfrm

Also these boards are known for bad soldier joints on the aluminum rails so I would check for that too.

I have repaired several of this style of PS/INV 4 to 3 to 2 transformer types. All of them have had at least 1 loose connection.

[Alastair E]

Re: Samsung LE32B450C4W smoking ccfl xfrm

Looks like a dry-joint on that Tx leg caused a burn-up.....

[notallbad]

Re: Samsung LE32B450C4W smoking ccfl xfrm

Thanks for the replies.

Was hoping not to have to tear down the bl panel but may have to just to be sure there are no bad lamps as suggested.

I believe the solder joint to have been made good as were the others though possible I may not have made a good enough job on that joint and caused the issue.