No backlights

[Mike Jenk]

So I have this Westing house LTV-27w2 and has the 2 seconds to black, can see image with light and has audio. I just wanted some input on the inverter board pin out CN2 , if some one has it to ensure my voltages are correct when turned on. If some one remembers where the post is for using another bulb in the place of mine could you let me know, I don't have any spares.

Thanks.

[tom66]

Re: No backlights

You have a Darfon board, any time you have 2 secs to black with a Darfon it is essential to check the transformers. See pic.

All transformers should measure with ±3% of each other. There may be a bad one on the board which measures otherwise.

edit: Check both sides of the transformer too, not just the side I highlighted in the image.

[Mike Jenk]

Re: No backlights

You have a Darfon board, any time you have 2 secs to black with a Darfon it is essential to check the transformers. See pic.

All transformers should measure with ±3% of each other. There may be a bad one on the board which measures otherwise.

edit: Check both sides of the transformer too, not just the side I highlighted in the image.

Thanks, I thought it might come to that, did a little research and these things are about 20.00 a pop. re-man board was about fifty and hate to have more problems later will let you known later, taking them out now.

[tom66]

Re: No backlights

Absolutely no need to remove them for the test, you can do it in circuit.

Likely, only one will have failed.

[Mike Jenk]

Re: No backlights

You have a Darfon board, any time you have 2 secs to black with a Darfon it is essential to check the transformers. See pic.

All transformers should measure with ±3% of each other. There may be a bad one on the board which measures otherwise.

edit: Check both sides of the transformer too, not just the side I highlighted in the image.

So I left one lead on terminal 1 then went around to each pin 2-8 and then repeated on all of them exactly the same way since the board is labeled with pin numbers. The transformer numbered as 1 in red measured between 1 and 4 had more then the 3% as compared to the other 6 transformer. I do not get 20K as you labeled. do they need to be removed to be more accurate. I really don't trust ohming things out in a circuit.

[tom66]

Re: No backlights

No, I meant you need to set your meter to 20k. They are typically 1-5k, can't remember exact figure right now. List all the readings you get on each transformer, and each side tested.

[Mike Jenk]

Re: No backlights

No, I meant you need to set your meter to 20k. They are typically 1-5k, can't remember exact figure right now. List all the readings you get on each transformer, and each side tested.

Transformer 1
Lead stays on pin1
2= 2m
3=2m
4=10.3k
5=11.1k
6=1.96m
7=1.99m
8=2.7k
Transformer 2
Lead stays on pin1
2=2m
3=1.99m
4=.3 ohms closed
5=981
6=1.99m
7=1.99m
8=977
Transformer 3
Lead stays on pin1
2=1.86m
3=1.86m
4=19.99k
5=20k
6=1.9m
7=1.99m
8=960
Transformer 4
Lead stays on pin1
2=1.91m
3=1.91m
4=.3
5=957
6=1.93m
7=1.93
8=950
Transformer 5
Lead stays on pin1
2=1.99m
3=2.01m
4=19.98k
5=20.93k
6=2.02m
7=2.02m
8=953
Transformer 6
Lead stays on pin1
2=2.17m
3=2.17m
4=.3
5=969
6=2.17
7=2.17
8=964
Transformer 7
Lead stays on pin1
2=2.1m
3=2.1m
4=10.3k
5=11.28k
6=2.1m
7=2.1m
8=960

I really appreciate helping me out, I have a ton of experience in Automotive, so I like to fix things.

[tom66]

Re: No backlights

You need to measure across the two pins I've highlighted only, and the other two opposite. No other measurements are necessary for now.

We see a lot of automotive techs here. I know how to change the oil and water in a car, but that's about where my knowledge ends...

[retiredcaps]

Re: No backlights

Transformer 1
Lead stays on pin1
8=2.7k

Transformer 1 pin 1 to 8 is bad. All the others in are the 950 ohms range.

[retiredcaps]

Re: No backlights

I had a 4006 transformer die on me too and I got it from this seller

http://www.ebay.com/itm/150706796810

[Mike Jenk]

Re: No backlights

Transformer 1 pin 1 to 8 is bad. All the others in are the 950 ohms range.

Thanks guys I really appreciate it. Will you let you know how it turns out.

[retiredcaps]

Re: No backlights

Actually, I just stopped at transformer #1 and didn't look at the rest, but now that I do, #3, #5, #8 are bad in addition to #1.

Have a look at this diagram.

http://www.lcdparts.net/TransformerD...ProductID=2739

Remeasure all the transformers and report just S1-S2 and S3-S4.

[retiredcaps]

Re: No backlights

Note some of the transformer pins might have a layer of "stuff". You may have to scrape off the "stuff" or get sharp probes to make good contact with the suspect transformers.

[Mike Jenk]

Re: No backlights

Note some of the transformer pins might have a layer of "stuff". You may have to scrape off the "stuff" or get sharp probes to make good contact with the suspect transformers.

Thats a good picture now I can see primary and secondaries. will report back in a few.

[Mike Jenk]

Re: No backlights

Note some of the transformer pins might have a layer of "stuff". You may have to scrape off the "stuff" or get sharp probes to make good contact with the suspect transformers.

Heres the results

Transformer 1
1/8=2.7k
5/4=960
Transformer 2
1/8=975
5/4=980
Transformer 3
1/8=960
5/4=960
Transformer 4
1/8=960
5/4=950
Transformer 5
1/8=940
5/4=954
Transformer 6
1/8=958
5/4=964
Transformer 7
1/8=955
5/4=950

[retiredcaps]

Re: No backlights

Heres the results

Transformer 1
1/8=2.7k
5/4=960
Transformer 2
1/8=975
5/4=980
Transformer 3
1/8=960
5/4=960
Transformer 4
1/8=960
5/4=950
Transformer 5
1/8=940
5/4=954
Transformer 6
1/8=958
5/4=964
Transformer 7
1/8=955
5/4=950

Okay, 1 is bad for sure. Scraping that stuff made a big difference in the other readings as you can tell for youself.

[Mike Jenk]

Re: No backlights

Okay, 1 is bad for sure. Scraping that stuff made a big difference in the other readings as you can tell for youself.

yes sir it did, can actually touch the legs, so I will get a new one and go from here. will measure it again when I remove it. sure is nice to have a diagram. Hate not knowing how something is wired. I really thank you guys for the help.

[Mr Bill]

Re: No backlights

I've got a few 4006A transformers in my basement if you don't want to wait 14 days getting it directly from hong kong on ebay.

[Mike Jenk]

Re: No backlights

I've got a few 4006A transformers in my basement if you don't want to wait 14 days getting it directly from hong kong on ebay.

That would be awsome. you can PM me for details.

[retiredcaps]

Re: No backlights

Get a couple so you have a spare just in case. The ones at the "top" of the TV seem to fail more often than others. On mine, it was the 2nd from the top.