need help to test inverter transformer

[woaimi]

Good day guys,
I have a Westinghouse model SK-32H540S, the one that most known for it bad inverter transformer 4302HXXXXX. Mine too, having that same problem the thing is there are 3 transformers on the inverter board 2 of them look clean although 1 of those clean looking has a burn mark on the board underneath the device, the 3rd one looks like busted with needle holes on top, cracked mark on a side and the melted stuff deposited outside. I used multimeter to test resistance as directed on LCDparts.net and found all 3 of them read the same values as of 1.8K between the Secondaries and 3 ohm between the primaries. My question is which one is the bad one? or is there another way to test these transformers? your suggestion is much appreciated.

-woaimi

[RON_CET]

Re: need help to test inverter transformer

I would remove all 3 inverter transformers off board to test,but the one you have mention with burnt marks underneath the transformer is bad more likely busted open from underside and need replacement,the 3rd one you mentioned with the crack and holes also is bad.So it sounds like you have two bad inverters and possible the third is ok provided the primary and secondary is reading correct resistance off the board

[woaimi]

Re: need help to test inverter transformer

Thanks RON_CET,
I had both the 1st (with burnt mark on board) and the 3rd with holes on top) removed and re-measured again just out of curiosity, they still read the same values as the 2nd (still mounted on board). I guess whatever happened the coils must have been undamaged and that's not necessary mean the transformers are still good right? So,, I'm gonna replace that 2 obvious for now to see if that fixes the problem otherwise I will replace out the 2nd as well. Could it be something else that causes the problem to begin with? from visually inspected, I see no blown caps on either this inverter board or power supply board. I checked the light bulbs with ohm's meter and there's continuity. The transformers are the only obvious suspect for now. Any idea?

[selldoor]

Re: need help to test inverter transformer

I am pretty sure you cant test ccfls with a ohms meter. - What did they measure?
Were they all the same? When you tried to switch the set on did they all flash.

[budm]

Re: need help to test inverter transformer

"I checked the light bulbs with ohm's meter and there's continuity"
I am not sure what you are reding, the CCFL should read open circuit, it is just vacuum tube with electrodes at each end.

[RON_CET]

Re: need help to test inverter transformer

for now replacement of the 2 defective inverter transformers is a start which hopefully will get you up and running provided if there not in damages to the drive area of the inverter but what your seeing is the most common failure with inverter transformers.

[woaimi]

Re: need help to test inverter transformer

selldoor & budm: I thought I saw some resistance indicated when probing the light bulbs connectors. I can definitely be wrong since this is my 1st touch to an LCD journey. Thanks for pointing it out. I'm learning.
RON_CET: I will try your suggestion tonight and will have either a "hooray" moment or more question tomorrow.

[selldoor]

Re: need help to test inverter transformer

I asked what resistance you got and if the lamps flashed as there may be a problem with the wiring. If it is shorted - and you did say there was continuity you could possibly damage the replacement transformers.
They should of course shut down pretty quick but best to check.

[woaimi]

Re: need help to test inverter transformer

I soldered the 2 new transformers into place, mounted everything, plug in power cable and see no life at all. what is the next thing to check?

[selldoor]

Re: need help to test inverter transformer

What do you mean by no life at all? To us that means there is no mains power to the machine - the first fuse has blown.

Might help if you could say what the original problem was- from plug in to stable faulty state as some us may have no experience of westinghouse.

Perhaps if we had some photos to work with?
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246


Please can you update your profile with country and mains voltage.

[woaimi]

Re: need help to test inverter transformer

Thanks selldoor, I will have some pictures uploaded later tonight. As for the tv, yep! seems like there no power to the machine but I got power read at the board entrance connector. There were no fuse that I can find which I find very odd for being a power supply & inverter board.
I take a step back to describe the background. This tv is actually belong to family in a community that I volunteered to work with. They were watching tv and it just shut down without any warning signs/ noise. Since I got some basic knowledge in electronic works, I offered to fix their if possible (no promises were made ) and gave them my son's 32" tube keeping the kids happy. Anyhow, that's how I end up with a this task and that's all I know about the original symptom.
thanks again and stay tuned for the photos

[woaimi]

Re: need help to test inverter transformer

I got a bit crazy at work, finally get sometimes to up load. So, the tv has 3 boards all together: a power/ inverter board, main board, and a tiny board called T-con board. Let me know what you find. Thanks

[retiredcaps]

Re: need help to test inverter transformer

If I may, let's start at the very beginning.

On the power board, there is a connector.

List the legend and your readings. For example,

pin 1 says 5V SB - I get 4.99V DC
pin 2 says 12V - I get 11.97V DC

etc

[popeye]

Re: need help to test inverter transformer

do exactly what retired says and also on the picture of the bottom side of the board i see burn mark this is probably due to that pin being dry jointed i hope you cleaned al the crap off that area or your new tranformer will not make contact,that dry was what caused the problem in the first place

[woaimi]

Re: need help to test inverter transformer

Thanks retiredcaps for that thought! I did just that and realized I'm getting no output from that connector. I worked it backward and found the missing link in continuity at the little component that I have always suspected for being a fuse from begining. It was indeed a micro slow blow fuse. I couldn't find any at local electronic shops so I ordered from amazon 10 PC's for $5. I'll update when I get the part, let's hope that will fix the whole thing. I'll attach the photo later so people with the same board can identify the component.

Have a festive independence day

Popeye, I'll take note of that and will make sure the area is well cleaned. Thanks

[retiredcaps]

Re: need help to test inverter transformer

I worked it backward and found the missing link in continuity at the little component that I have always suspected for being a fuse from begining.

On the pcb board, there are designators to tell you what the components are. Fuses are usually "F". For example, F100.

http://en.wikipedia.org/wiki/Electro...e_designations

It was indeed a micro slow blow fuse. I couldn't find any at local electronic shops so I ordered from amazon 10 PC's for $5.

Most people here recommend digikey.com for electronic parts. For USA customers, First Class shipping is a very reasonable $2.75 USD ish and parts usually arrive in 48 hours.

I'll update when I get the part, let's hope that will fix the whole thing.

Sometimes a fuse blows due to age. Sometimes not. If you replace the fuse without testing some of the other components, you will be using up those 10 fuses quickly.

Have a festive independence day

[woaimi]

Re: need help to test inverter transformer

back from a little summer trip and still waiting for the fuse order to arrive!

I failed to realize that at the first place until seeing your post, I looked at the board again and there it was i guess i learned the hard way. I went to digikey and order another 25 just in case. I'm sure it could be something else that causing the fuse to blow but I'll start from here and hopefully it solves the problem. What might be the next thing to check?

[retiredcaps]

Re: need help to test inverter transformer

What might be the next thing to check?

Circled in red is your bridge rectifier. Circled in yellow is your mosfets. Check both for shorts

I have written procedures on how to check both at least 30 times so search around here.

[woaimi]

Re: need help to test inverter transformer

well, i got the fuses, soldered it in and it blown instantly, so I followed your suggestion. the rectifier is good but I couldn't confirm the mosfets (following your ohm method) as each time i try i get different result.

[multimeter]

Re: need help to test inverter transformer

well, i got the fuses, soldered it in and it blown instantly, so I followed your suggestion. the rectifier is good but I couldn't confirm the mosfets (following your ohm method) as each time i try i get different result.

change the battery in your multimeter,and confirm it reads "1" or "0L" when shorting the probes together, set to 200ohm setting