Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

[SuperSkippy]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

Me again.

So, I've got the new power supply board. As you can guess by the fact I'm still posting, it still doesn't work.

With the new PSU, the power just blinks- it never turns on the backlights at all. Voltages on the new PSU seem good.

I think it has to be the inverter, or maybe the backlights.

I am depressed :-(

[tom66]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

Question is, is the ripple still there?
Maybe the PSU is faulty? They are scrap pulls from smashed screen TVs.

[SuperSkippy]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

Question is, is the ripple still there?
Maybe the PSU is faulty? They are scrap pulls from smashed screen TVs.

We never get far enough to see the ripple with this one. With this one, you apply power, and the blue power light flashes over and over again- it's like it's detecting a short and just restarting over and over again. If you attach car lightbulbs to it rather than the inverter though it stays up. You get not a lot of ripple in that case.

I admit the new PSU could be bad, but what are the chances of me having found two power supplies that can supply the right voltages when loads are attached, but can't keep my TV running when the inverter is plugged in?

[tom66]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

Yeah, I have to admit that's odd -- but on the other hand, I have often found there can be common defects with a series of TVs.

Have you tried budm's bulb trick?

[SuperSkippy]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

See attached a photo of a couple of transformers on the inverter board. Does the one of them look bad to you- it's got some orange goo coming out of one of the corners. I think it might measure resistance a bit low, but I'm finding them hard to measure in circuit.

[tom66]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

That's just glue.

For these transformers you test top left to bottom left, as one winding, then top right to bottom right as another.

[budm]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

Oh no, DARFON transformer!

[tom66]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

Budm's fear is not misplaced.
I have a small collection of the ones I have replaced. Darfon should be ashamed!

[budm]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

"I've tested all of the transformers and all of the resistances of each of the coils are correct. " How close are the resistance reading? Within 3%.
Also those small green lytic caps, I would check them real close also, ran into them on ACER inverter board. After heating up the caps for a while with hair dryer, the backlights stay on instead of black out after 2 seconds.
https://www.badcaps.net/forum/showth...455#post288455

[SuperSkippy]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

"I've tested all of the transformers and all of the resistances of each of the coils are correct. " How close are the resistance reading? Within 3%.
Also those small green lytic caps, I would check them real close also, ran into them on ACER inverter board. After heating up the caps for a while with hair dryer, the backlights stay on instead of black out after 2 seconds.
https://www.badcaps.net/forum/showth...455#post288455

So here's the thing- I was trying this yesterday and I was having a hard time getting a resistance readings from the primary of these transformers. If I put the probes across the primary, it seems to go from open circuit, to 4 ohmsish, to 16ohms is, then back to open circuit, then from 4 ohms to 16 ohms again... (Edit: reading Tom's post, maybe I'm doing it wrong).

They all seem to do the same thing though.

I've tried testing all the "green" electrolytic caps across the bottom of the board (they're not green on my board, they're brown), but they are in parallel, so it's difficult to test them individually without desoldering them all. Do you think it's worth doing that?

[budm]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

We rarely see bad primary side, it can be as low as less than 1 Ohm, its the secondary side that fails.

[SuperSkippy]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

I've found a bad transformer!

I've also found a schematic diagram for the inverter board as made by Darfon. You can get it here:

For these transformers you test top left to bottom left, as one winding, then top right to bottom right as another.

I don't think that's true. Using the schematic and by looking at the transformer I removed, I worked out the following pinout, where 1 is the blue dot on the top.

1- Secondary 1
2- Primary 1
3- Primary 2
4- Secondary 2
5- Secondary 2
6- Primary 2
7- Primary 1
8- Secondary 1

On this inverter board, pins 2 and 3 are joined, and pins 6 and 7 are joined to join the primaries in parallel.

Pin 1 and pin 4 are joined to make the secondary go from pin 8 to pin 5, and pin 1 and 4 is a centre tap.

You can see how this is wired using the schematic diagram.

I was getting around 2k between pins 5-8, made up of 1k between pin 5 and pin 4 and another 1k between pin 1 and pin 8.

On one of the transformers, I've got one secondary at 18k, rather than 1k. I'm going to try and swap it.

Just for reference (and maybe google), my transformer has the part number 4015A504011 (GP) written on it.

[SuperSkippy]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

Budm's fear is not misplaced.
I have a small collection of the ones I have replaced. Darfon should be ashamed!

Out of interest, how did you diagnose that the inverter board had bad transformers?

[tom66]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

The secondary resistance was twice or more of the others.

And I have replaced four, on four separate inverters. Usually only one goes after 3~5 years due to a consistent manufacturing defect.

[budm]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

When you see DARFON on the board, first thing to check will be the transformers, how many time I have seen this, that is why I always ask about how they are tested to be OK.

[SuperSkippy]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

This thread is back from beyond the grave.

OK, so now I've got my replacement transformers. I bought them from eBay (http://www.ebay.co.uk/itm/2710080382...84.m1439.l2649)

I've soldered them in. It still doesn't work. The TV power supply just clicks now.

It has a slightly different resistance on the secondary- 1.4k rather than 1k on the original transformers on the board.

a) D'ya reckon these transformers are no good? They say 4015A on them like the ones I'm trying to replace?
b) Where do you get your replacement transformers from, rather than Chinese eBay sellers that take a month to ship them?

[tom66]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

Those transformers are the wrong type, I have had it before when trying to replace 4008A ones, there are ones with different secondary resistances but no obvious markings.

[SuperSkippy]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

Marv.

Where do you buy yours from?

[tom66]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

eBay from a US seller, but I got my money back (eBay dispute) and went for the slightly more expensive UK seller.

[SuperSkippy]

Re: Toshiba 30" TV 30wl46b TV 2 seconds to black(ish)

Sorry about digging this thread back from the grave, but I thought it would be useful to post a conclusion- I got another Darfon inverter transformer from CHS, and that made the TV work again.