Westinghouse SK-32H5405 troubleshooting using CCFL probe

[budm]

Got this Westinghouse SK-32H5405 in today with 3-second to black, I was able to use my CCFL probe to locate the problem using the CCFL probe. The problem found is one of the two high voltage winding of the inverter transformer has no high voltage output, the winding has open circuit as you can see, the board also has burnt spot. The good windings light up the test lamp fine.
This is the second time I use this probe on the TV with 3-second to black symptom.
https://www.badcaps.net/forum/showth...x+dx-40l261a12

[Shinju]

Re: Westinghouse SK-32H5405 troubleshooting using CCFL probe

Ugh, I got one of these...... Replaced all transformers and still no backlight.

[The Performer]

Re: Westinghouse SK-32H5405 troubleshooting using CCFL probe

Im not following completely how this technique works, did you simply solder a probe to a cfl bulb and it safely tests the high voltage ac output of transformers? Or is there more that I dont understand going on?

Thanks!

[budm]

Re: Westinghouse SK-32H5405 troubleshooting using CCFL probe

Just solder solid wire to the center of the lamp base, and just put the probe on the high voltage output terminal of the inverter socket, that is all.
You can also use this:
http://s807.photobucket.com/user/bud...?sort=3&page=1

http://s807.photobucket.com/user/bud...?sort=3&page=1

[aaronwt6]

Re: Westinghouse SK-32H5405 troubleshooting using CCFL probe

Bud,

Just wanted to add something to this thread that I think is interesting. I've repaired several of these boards myself. Same problem, one bad inverter transformer. What I find odd though is that every one I've fixed has been the same transformer closest to the main board connector, as is yours. I see absolutely no reason that one should be getting any more stress than the others but I'm talking like 6-7 of these and now I see yours is the same as well. Any opinion on why that might be?

[aaronwt6]

Re: Westinghouse SK-32H5405 troubleshooting using CCFL probe

Oh, and to add to this. It was obvious on all which one had failed. Board discoloration at the point of failure. Some even showed through slightly on the bottom.

[budm]

Re: Westinghouse SK-32H5405 troubleshooting using CCFL probe

The primary side of the transformers are connected in parallel, the burnt out is one the two windings of the secondary side so I do not know why it is always that one, the lamp for that winding was drawing too much current? I do not know, something is out of balance some where.

[Shinju]

Re: Westinghouse SK-32H5405 troubleshooting using CCFL probe

Isnt there a protection circuit on this board that fails and would cause the CCFL's to not light up even if the inverter side is all up and running?

[aaronwt6]

Re: Westinghouse SK-32H5405 troubleshooting using CCFL probe

Isnt there a protection circuit on this board that fails and would cause the CCFL's to not light up even if the inverter side is all up and running?

The ones I had would all flash for a second or so then go dark.

But I do think it's quite strange that they all had that same one go. I'm in agreement with you on they way they are connected Bud. Seems that it would be random.

[Shinju]

Re: Westinghouse SK-32H5405 troubleshooting using CCFL probe

My Darfon failed on the bottom transformer closest to the power connector.

[aaronwt6]

Re: Westinghouse SK-32H5405 troubleshooting using CCFL probe

My Darfon failed on the bottom transformer closest to the power connector.

Well, there ya go. Blew my perfect record out.

[Shinju]

Re: Westinghouse SK-32H5405 troubleshooting using CCFL probe

Mine was pretty bad, blew a hole through the board. I tried to fix it, the panel comes on there is a picture and sound but no CCFL activity at all.