Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

[budm]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

"Errr... is it safe to use a WORKING cfl for this test ?" Yes, that will fine too. I use both, non working and brand new.

[vinceroger69]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

"Errr... is it safe to use a WORKING cfl for this test ?" Yes, that will fine too. I use both, non working and brand new.

budm can you comfirm i can just take a brand new cfl solder one wire to the centre on the bottom and use it to test i dont have to take the new cfl apart to remove the circuit board etc cheers.
as i have just read some of the previous posts.

[budm]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

Yes, that is correct, this is the high voltage probe for finding out if the high voltage output of the inverter is working or not or if one is weaker than another. The other inverter test lamp that you have to take apart and hook up both wires to the inverter out put is for real load test. This probe is just for quick test to find out if you do have high voltage output or nor or if one output is less than the other. Using this probe will not stop the the inverter circuit going into 2-second to black.
This probe is good when you have lots of transformers on the inverter that you are not sure which one is bad, especially if all the DCR show OK as shown in this inverter. At first I thought I may have lamp problem because the resistance of the winding show OK, using this probe help me from taking the panel apart to check the lamp which as it turns out to be not the case. It is just one of the tools I use now.
You can also use this kind of lamp.

[vinceroger69]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

Yes, that is correct, this is the high voltage probe for finding out if the high voltage output of the inverter is working or not or if one is weaker than another. The other inverter test lamp that you have to take apart and hook up both wires to the inverter out put is for real load test. This probe is just for quick test to find out if you do have high voltage output or nor or if one output is less than the other. Using this probe will not stop the the inverter circuit going into 2-second to black.
This probe is good when you have lots of transformers on the inverter that you are not sure which one is bad, especially if all the DCR show OK as shown in this inverter. At first I thought I may have lamp problem because the resistance of the winding show OK, using this probe help me from taking the panel apart to check the lamp which as it turns out to be not the case. It is just one the tools I use now.

cheers budm thats the answer i was looking for well explained.

[senderj]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

Budm, other than my hands, can I use something else? Like a wire to the E of the power plug?

[budm]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

It depends on the stray capacitance on the glass and the wire to the chassis, you will have to make sure you get good contact to the high voltage output pin, you can wrap 4~5 turns of wire on the glass of the lamp and see if it will give enough capacitance to light up the lamp.

[paulstef]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

At first I thought I may have lamp problem because the resistance of the winding show OK,

In your first post you mentioned one of the transformer windings was faulty. Do you remember what exactly it was? If the secondary resistance was ok, what exactly was wrong with it? Primary short between windings? Short between secondary/primary?

[budm]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

It has burnt high voltage winding as you can see in the last picture, it was not open winding.

[paulstef]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

It has burnt high voltage winding as you can see in the last picture, it was not open winding.

Ok, thanks. I just wondered how the resistance was reading ok but the transformer secondary still has interwinding shorts. I would expect it to be at least slightly lower.

That's because the transformer outputs in my case, 4 in total, have exactly the same resistance...

EDIT.: No, it does not have the exactly same resistance. One winding has 537Ohms instead of 575Ohm like the others. And it looks like the one in the picture of your first post. That will be it. Great! Now, they COULD make their circuits a little less sensitive, I mean tha's only a 7 percent loss in resistance...

[stj]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

7% of 2-3kv is 200v !

[paulstef]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

7% of 2-3kv is 200v !

Yeah I know, I mean if the backlight works for 2 seconds they could easily make the circuit in a way to leave it on for longer.

[budm]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

Added info:
"do you leave the existing bulbs connected" Yes.
"Do you touch the bulb on a secondary winding post?" Yes.
What I look for is if all the output will light up the test lamp at the same brightness, the one test point that does not will be the one to suspect as bad, as you can see that the bad one in my post the lamp lights up dimly. I did not run into any inverter with bad transformer since I made this probe to use this method to find out if it is useful or not.
I also use to verify if the inverter even fire up at all for second or not instead of trying look the holes in the back of the LCD panel.
Using it on the inverter with just one transformer instead of many transformer for each lamp will not help much, it will only indicate you do have high voltage or not, it is good for multiple transformer type inverter.

[jonnyred06]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

Found same problem in my dynex with the burnt winding on the inverter high voltage transformer. Is this something I can find, buy, and replace?

Thanks!

[SteveNielsen]

Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer

The lamp is one of those broken lamp that I solder a solid wire to the base of the lamp and no need to take the lamp apart, it can be 120 0r 230V CFL, the high voltage will just goes through the lamp circuit (due to stray capacitance) and through the lamp glass due to stray capacitance of your body while you are holding it with you hand, Just remember that we are dealing with high frequency AC, any stray capacitance inside the lamp will have low reactance.
Ever try holding the fluorescent lamp close to high frequency generator?
This is an old trick I used to find out if AC High frequency generator is working or not (I used to repair lots of PLASMA Etcher for semiconductor industries), on the high power the lamp does not even have to make contact with the source, just put the glass body close to the source and it will light up.
You can also use this:
http://s807.photobucket.com/user/bud...tml?sort=3&o=1

I have a negative ion generator that emits -9KV with respect to ground. Touching the base of a bad CFL (either shell or tip) to the ion emitter point will light the bulb in flashes as it shocks my hand holding the glass in audible arcs, thankfully not enough current to damage anyone. It flashes even brighter when the bulb is discharged directly to ground after doing this. Amusing at least.