need help to test inverter transformer

[woaimi]

Re: need help to test inverter transformer

It was verified as 452nF, that's what happened when I tried to work on it at 2:00 am. So, going back to your drawing, if I can't measure those 2 points you mentioned how can I verify it 0 voltage? I'm feeling very close to get it working, really don't want to throw in the towel yet.

[woaimi]

Re: need help to test inverter transformer

thanks budm for pointing it out, i will have it verify later tonight, I might have mis-read the 'u' and 'n' on the meter.

[budm]

Re: need help to test inverter transformer

It is 0.47uF cap not 0.47nF.

[woaimi]

Re: need help to test inverter transformer

Wow, thanks for that drawing, I've learned much more since I take on this project. Thanks for all those replies.
I checked the light bulbs one at a time and they're all flashed up in the same pattern; it flashes like twice in about 5 seconds, I think they are fine.
The DC blocking cap were removed to test, it read opened when test with the ohm meter and the capacitance measured 0.452 nF and the caps's label said 474K (I'm guessing that 's a 0.47 nF cap)

[budm]

Re: need help to test inverter transformer

OK, I looked at the inverter/power supply board, all three transformers are driven by the same output MOSFET's. I still think you should have replace all 3 transformers.
You have indicated that you have 56V at all time on the inverter transformers primary side. It should have 0 Volt due to DC blocking cap, and the junction between the two inverter MOSFET's should have 0V (not 100% sure since I did not draw out the circuits in details). I would take that blue DC blocking cap out and measure for any leakage resistance using the highest Ohm scale, cap should show open circuits, you should also check its capacitance.
Another thing you can check to see if all the lamps do at least try to light up or not by just having one set of lamp connector connected one at a time, then turn on the TV in the dark room and see if each set of the lamp will light/flash.
I will tell you later how to use home made tester lamp.

[woaimi]

Re: need help to test inverter transformer

I measured the Vcc input to the transformers and reading 56v at all time whether the TV is on nor not, does that suggest anything?

[selldoor]

Re: need help to test inverter transformer

I am hoping all transformers will be good and we can work out which lamp or lamps is
causing the shut down. As I said budm has more ideas on this and has a way of using
old domestic energy saving bulbs to test so we need to hope he comes back to this thread. For testing the size of your panels doesnt matter I think you can get adapter from small to big but for now just see if you can plug a small plug in onto one pin of the big connector. If it will go on then we can consider cutting the small plug in half.

[woaimi]

Re: need help to test inverter transformer

that is my problem right now, I couldn't find anything with that plug, my bulbs mostly came from computer LCD and the biggest size i have is 19". There are 6 plugs for this tv set and I'm assuming it represent 6 bulbs, here's what I'm thinking will I cause any damage if I only plug in 1 or 2 bulbs to the corresponding transformer and leave the other unplug? this way I can verify which transformer is working and which one is not and may be at the same time can figure out the questionable bulb/s.

[selldoor]

Re: need help to test inverter transformer

good - were you able to find a panel with that type of backlight connector?
If not ,I am not sure how the Big plugs are wired -perhaps budm will suggest how you
can best test the bulbs

[woaimi]

Re: need help to test inverter transformer

I get 1.7K -1.8K ohm on all 3 transformers on board

[selldoor]

Re: need help to test inverter transformer

Well, that is a bit different - can you do 1>2 and 3>4 on the other transformers ( Leave them on the board)

[woaimi]

Re: need help to test inverter transformer

ok this what i got out of 1 transformer. I labeled the pins in the photo.

1>2=1.77k / 1>all other 8 pins = OL

2>all pins = OL

3>4= 1.77k / 3> all pins = OL

4> all pins = OL

5> all pins = OL

6>7= 2.9 ohm; 6>8=5.3 ohm; 6>9= OL

7>8= 2.9 ohm; 7>9= OL

8>9= OL

[woaimi]

Re: need help to test inverter transformer

wow, it'll be lots of numbers to play with

[selldoor]

Re: need help to test inverter transformer

Ok - you will have to do it the long way
1>2 1>3 1>4 1>5 1>6 1>7 1>8
2>3 2>4 2>5 2>6 2>7 2>8
3>4 and so on - Just record the high numbers.

[woaimi]

Re: need help to test inverter transformer

yeah, all 3 meters gave me the same result, 2 of them on auto, the other was set to 2000 ohm. the thing is i don't think the winding goes in that pattern cause I get the same reading from all 5 transformers (3 existing and 2 new)

[budm]

Re: need help to test inverter transformer

Yes I wonder about those reading too, pretty hard to break the primary winding since they are pretty good size wire gauge compared to very fine wires on the secondary side.

[selldoor]

Re: need help to test inverter transformer

I measured the transformers according to your diagram and got "OL" on all pairs
s1-s2=OL
s3-s4=OL
p1-p2=OL
p3-p4=OL

Can you test your meter - is battery ok- it is very unusual for all 4 windings
to be open. Was it on 2000 ohms Make sure you are testing on bare metal.

[woaimi]

Re: need help to test inverter transformer

I measured the transformers according to your diagram and got "OL" on all pairs
s1-s2=OL
s3-s4=OL
p1-p2=OL
p3-p4=OL

I have not get a chance to test with light bulb but will follow up and keep you posted
thanks

[selldoor]

Re: need help to test inverter transformer

Please measure as per my diagram - ignore the other pins.
I have to go out now but you can get a panel that might have good bulbs in
thet would be great - even better if they have the sme connectors- doesnt usually matter about the size of the bulbs for a short test.

[woaimi]

Re: need help to test inverter transformer

I have many old lcd screen to be used just nothing with that size. I don't think the bulbs or lcd is bad though, because the whole screen actually came on for a short time and went away. My guess is the transformers but I couldn't find any info about this transformer. My is a little different than the one on your photo; it has 9 pins. I replaced 2 out of 3 because they look like they melted but even those 2 gave me the same reading as suggested by lcdparts.net
i will have the transformers measurement later tonight.