Beko 30WLB500S - Sound, no picture

[Th3_uN1Qu3]

Re: Beko 30WLB500S - Sound, no picture

I wouldn't try to do that. Strike voltage is over 1.5kV and may, scratch that, WILL damage your multimeter. Plus, if you haven't got a true-RMS multimeter (or an analog one), it'll lie to you, because the CCFLs run on high frequency AC.

[tmcw]

Re: Beko 30WLB500S - Sound, no picture

Alright, back again after another bout of testing, and looking for some more advice. Even though all 3 TV sets have the same model number, the internal boards are slightly different, and possibly not all interchangable between 1 and the other 2.

One thing in common was that the power boards are all the same, and all have/had bulging caps, which is easily sorted.

*******************
Set 1 differed from the other 2 in both the inverter (different physical size and placement of chassis screws - Invert_comp.jpg) and the connection from the AV board to the LCD panel (smaller, though number of used pins is the same). The panel is good, the power board can be recapped, but the inverter has one bad transformer. The numbers on the transformers are all slightly different - can someone advise what I need to get to replace? An example of the one that is faulty is 4006A422096.

I will try to get the inverter working, so ultimately set 1 will be essentially original.

*******************
The other 2 sets appear to be more similar. I eventually got together a combination of parts that has been "working" for the past few hours.

The first inverter I tested, I reported the resistance in the transformers already, all ok, and averaged about 930 ohms at each location. The other inverter tested much better, about 1030 ohms each and all ok, closer to the 1000 expected by Bill. I couldn't get the 930 one to work (2 seconds to black), but the 1030 one is working great. I've attached a photo of the 2 (Sim_inverters.jpg, bottom is 1030 ohm one). I'm wondering about whether it's possible to fix the 930 one, would it mean replacing all the transformers, or any other possibility there?

The next issue is with the LCD panels between these 2 sets, one has the front smashed, the other is intact, but has a few vertical lines on it (LCD_Panel.jpg). You can see a few lines at the "e" in "nickel", a few more at the "de" in "nick.de", and a whole bunch of them further over to the right. Other than those, the screen is pretty good. The panel may have been dropped face-first into a plastic crate with a bit of water at the bottom, so would this water have caused this problem? What I'm mainly wondering is if it's more likely an issue with the electronics to the LCD that might be at fault, so maybe some electronics from the panel with the smashed screen might be of some use? Worth trying? The smashed screen was coming on for 2 seconds with all known other good parts, so would it be worth salvaging parts from it? I did try reseating the 4 ribbons (LCD_Board.jpg) from the LCD board to the edge of the panel, but it didn't make a difference.

[PlainBill]

Re: Beko 30WLB500S - Sound, no picture

On the inverter transformer P/N 4006A422096. The 4006A is significant, the 422096 or whatever is a production lot or date code.

Measuring resistance is a crude approach to what we are really trying to do - determine if the transformer has shorted turns. A better method would to use a ring tester, but only us old TV types have them on hand. If the transformers were wound with a slightly different gauge of wire the resistance would be different, but as long as the turns ratio was the same they would work perfectly. I had exactly that situation with one TV I repaired - except for one, the originals read very close to 1K. The replacement read just under 900 ohms, but worked perfectly.

The vertical lines are caused by a bad bond between the ribbon cable from the Tcon and the glass panel. Sometimes they can be fixed by applying pressure.

PlainBill

[tmcw]

Re: Beko 30WLB500S - Sound, no picture

As ever, thanks Bill for the helpful information.

I've had a search for the 4006A, and can see the parts available, less painful than I was thinking it might be. All the windings except one are of the 960-970 ohm range, with the bad one reading 4.7k ohm, so is it true to say that transformers don't go bad gradually, that their failure is usually catastrophic?

Great info on the inverter transformers. So if it's possible that they were all 930 ohms to begin with, what else should I be looking at that's causing the inverter to give the 2 seconds to black? The caps?

I'll have a look at the panel this afternoon, see if I can see any place where the contacts might be coming away. That set looked like it was dropped as well as dunked, as the top-left corner showed signs of an impact. It's funny, it's not too bad, and the worst of it isn't visible if looking at 4:3 transmissions, but I'll have a look.

[Th3_uN1Qu3]

Re: Beko 30WLB500S - Sound, no picture

All the windings except one are of the 960-970 ohm range, with the bad one reading 4.7k ohm, so is it true to say that transformers don't go bad gradually, that their failure is usually catastrophic?

The only failure modes of a transformer are shorted turns or arcing (which can lead to either shorted or open turns, or something in between - an arc burns stuff and carbon is conductive). Both types of failures will occur in cascade - once it's started, it'll get fried in a matter of minutes. Even less at wire gauge of an inverter transformer and the voltages it runs at.

[PlainBill]

Re: Beko 30WLB500S - Sound, no picture

Simple rules. A group of transformers with identical numbers (INCLUDING the production codes) were wound at the same time and should have identical resistances. This should not change over the life of the transformer.

Both secondaries on a 4006A or similar transformer should match to within 3%

Transformers from different production lots may have minor (3-5%) differences in resistance.

Transformers from two different factories may have major differences in resistances. Again, if both secondaries on a 4006A type transformer match to within 3%, the transformer is probably good.

There is no need to look beyond the transformer. Replace it, the inverter should work.

PlainBill

[tmcw]

Re: Beko 30WLB500S - Sound, no picture

Simple rules. A group of transformers with identical numbers (INCLUDING the production codes) were wound at the same time and should have identical resistances. This should not change over the life of the transformer.

Both secondaries on a 4006A or similar transformer should match to within 3%

Transformers from different production lots may have minor (3-5%) differences in resistance.

Transformers from two different factories may have major differences in resistances. Again, if both secondaries on a 4006A type transformer match to within 3%, the transformer is probably good.

There is no need to look beyond the transformer. Replace it, the inverter should work.

PlainBill

Thanks for that info. I think there may be a bit of confusion, which is not to be unexpected given that I was working with 3 slightly different sets of the same model.

One of the inverters has a problem with one of it's transformers, that's the 4006A replacement that I need to get for that inverter. This inverter is very different to the other 2 inverters.

Of the other 2 inverters (which are slightly different in design, but share the same number 48.V1448.001, but end in /F or /J, and have different transformer numbers, 4009A or 4015A) one is working in a TV set, but the other does not, even though all the transformer windings on that inverter are showing similar resistance results (post here). That inverter has transformer numbers 4009A. This is the inverter I'm wondering about, if all the windings are seemingly ok, what else is there to go wrong on the board, the caps maybe?

[PlainBill]

Re: Beko 30WLB500S - Sound, no picture

Thanks for that info. I think there may be a bit of confusion, which is not to be unexpected given that I was working with 3 slightly different sets of the same model.

One of the inverters has a problem with one of it's transformers, that's the 4006A replacement that I need to get for that inverter. This inverter is very different to the other 2 inverters.

Of the other 2 inverters (which are slightly different in design, but share the same number 48.V1448.001, but end in /F or /J, and have different transformer numbers, 4009A or 4015A) one is working in a TV set, but the other does not, even though all the transformer windings on that inverter are showing similar resistance results (post here). That inverter has transformer numbers 4009A. This is the inverter I'm wondering about, if all the windings are seemingly ok, what else is there to go wrong on the board, the caps maybe?

In no particular order, a few possible causes are an open fuse, bad capacitor, shorted driver, bad transformer.

'the other does not work' describes a problem, not the symptoms. 'Doc, I'm not feeling well' doesn't convey much information. 'Doc, I've had a pain in my stomach for a month, and Malox doesn't help.' takes a few more words, and conveys a wealth of information.

PlainBill

[tmcw]

Re: Beko 30WLB500S - Sound, no picture

In no particular order, a few possible causes are an open fuse, bad capacitor, shorted driver, bad transformer.

'the other does not work' describes a problem, not the symptoms. 'Doc, I'm not feeling well' doesn't convey much information. 'Doc, I've had a pain in my stomach for a month, and Malox doesn't help.' takes a few more words, and conveys a wealth of information.

PlainBill

Heh, sorry, I do try to be descriptive, that one slipped through.

With that inverter in, it does 2 seconds to black.

The transformers all give the same resistance (roughly 930 ohms), and the 4 fuses are ok.

The 12 electrolytic caps are "NKCON"s, 100uF/35V (the later revision inverter that works uses 10 Nichicons 82uF/35V).

Is the driver a chip, or chips associated with each transformer?

There's nothing visibly blown/damaged on the board.

[PlainBill]

Re: Beko 30WLB500S - Sound, no picture

Heh, sorry, I do try to be descriptive, that one slipped through.

With that inverter in, it does 2 seconds to black.

The transformers all give the same resistance (roughly 930 ohms), and the 4 fuses are ok.

The 12 electrolytic caps are "NKCON"s, 100uF/35V (the later revision inverter that works uses 10 Nichicons 82uF/35V).

Is the driver a chip, or chips associated with each transformer?

There's nothing visibly blown/damaged on the board.

The prime suspect would be capacitors. I'm not sure of NKCON caps - they may be good or bad.

It's possible you have an open driver; a shorted driver (the usual failure) would likely blow a fuse.

A good test at this point would be to hook a single CCFL up to each output in turn and see if it lights up. If it fails to light in a single position there could be a problem with a component in the protection circuit.

PlainBill

[tmcw]

Re: Beko 30WLB500S - Sound, no picture

Thanks for the test.

I put the faulty inverter in the set that was working, and connected each of the 8 connections to the CCFLs in turn. In each case, the panel lit up, and 1 or 2 seconds later went black.

[tmcw]

Re: Beko 30WLB500S - Sound, no picture

...
The vertical lines are caused by a bad bond between the ribbon cable from the Tcon and the glass panel. Sometimes they can be fixed by applying pressure.

PlainBill

I took the panel apart, and found that there were residues of the panel's dunking in the water. There were also dust and fibre accumulations around the flexible connections that I can only liken to the way branches and debris gets stuck around bridge buttresses during a flood. I cleaned it up, but also noticed that most of the lines were visible in the panel even with it off, so there is some irreversible damage to that panel. The bigger cluster of bad lines (which go all the way from top to bottom) towards the right of the panel improved a bit, so they can probably be sorted if I take the panel apart again, and do something to improve the connection. I also noticed some pin-head patches in one small portion of the panel, which appear to be inside the LCD panel. Reminded me of mould; is that possible?

Anyway, I had a look around and can see replacements for upwards of $90 for the panel, to $300 for panel, CCFLs, diffuser, LCD and inverter board, but not sure it's worth splurging $90 (+ shipping) for the panel. I might be lucky and find one much cheaper at some stage.

During the search for a replacement panel (which is a CHI MEI V296W1-L14), I did see a V296W1-L11 for a reasonable price. Would these be compatible?

[PlainBill]

Re: Beko 30WLB500S - Sound, no picture

I took the panel apart, and found that there were residues of the panel's dunking in the water. There were also dust and fibre accumulations around the flexible connections that I can only liken to the way branches and debris gets stuck around bridge buttresses during a flood. I cleaned it up, but also noticed that most of the lines were visible in the panel even with it off, so there is some irreversible damage to that panel. The bigger cluster of bad lines (which go all the way from top to bottom) towards the right of the panel improved a bit, so they can probably be sorted if I take the panel apart again, and do something to improve the connection. I also noticed some pin-head patches in one small portion of the panel, which appear to be inside the LCD panel. Reminded me of mould; is that possible?

Anyway, I had a look around and can see replacements for upwards of $90 for the panel, to $300 for panel, CCFLs, diffuser, LCD and inverter board, but not sure it's worth splurging $90 (+ shipping) for the panel. I might be lucky and find one much cheaper at some stage.

During the search for a replacement panel (which is a CHI MEI V296W1-L14), I did see a V296W1-L11 for a reasonable price. Would these be compatible?

Sorry, I have no idea.

PlainBill

[tmcw]

Re: Beko 30WLB500S - Sound, no picture

It seems as though they are the same, I've since found spec documents for both versions, and the data in the pdfs are identical, except for the number in the header on each page, and the engineering drawings had a slightly different orientation, but appear to be the same. There may be more that are compatible, it'll give me a better chance perhaps at getting a panel at a reasonable price later on.

For me, the real pleasure is in bringing them back to life, at the least cost possible, and learn a bit about how they function in the process.

[tmcw]

Re: Beko 30WLB500S - Sound, no picture

Ok, back again after having recapped all 3 power supply boards, with all caps replaced except the big one.

2 of the boards are now good, giving correct voltages and powering up the TV set with no issues.

The 3rd power supply was also recapped, but found to be dead. Further testing found that the PCB fuse (F1 on the mains input, red cylinder, top right section in this picture here was blown. It's one of these.

I didn't have any replacement, so desoldered one of the good ones from a good board and swapped it in. Upon power-up, the power board blew the fuse in the power cable plug, and tripped a switch on the distribution board, but the F1 fuse is still intact.

Now, I have 2 working power boards, but would still like to get the 3rd functional as a backup if possible, so any further direction in what to test, what's likely to be at fault, I'd be grateful for any help.

[Dgtech]

Re: Beko 30WLB500S - Sound, no picture

For me, it's good news whenever I find a blown fuse. Now it's time to play the "Find a shorted component" game. Which picture was the one of this power supply?

[Th3_uN1Qu3]

Re: Beko 30WLB500S - Sound, no picture

Responding to the above posts: NKCON caps are bad.

[tmcw]

Re: Beko 30WLB500S - Sound, no picture

I was looking for replacements to the NKCONs at my local place (radionics), but couldn't find the caps with the same uF/V AND same dimensions. What would be the recommendation for replacements, closer to the same length or diameter?

All 3 power supply boards are the same, so it might be easy enough to compare some components, I don't know where best to start though. I've attached photos of the early part of the power supply board, both sides.

I took the F1 off the board, and put it back on the good board, so are there any tests I can do without having to power up the board, at least until I can get a replacement fuse?

[PlainBill]

Re: Beko 30WLB500S - Sound, no picture

I was looking for replacements to the NKCONs at my local place (radionics), but couldn't find the caps with the same uF/V AND same dimensions. What would be the recommendation for replacements, closer to the same length or diameter?

All 3 power supply boards are the same, so it might be easy enough to compare some components, I don't know where best to start though. I've attached photos of the early part of the power supply board, both sides.

I took the F1 off the board, and put it back on the good board, so are there any tests I can do without having to power up the board, at least until I can get a replacement fuse?

Primary suspects are the bridge rectifier and the power FETs. There appear to be a couple of extra diodes, those should be checked too. Concentrate on the primary side of the transformers.

PlainBill

[tmcw]

Re: Beko 30WLB500S - Sound, no picture

Ok, did a few tests.

On the bridge rectifier BD1, I was getting about 0.5 as normal (using guide from here), but when I reversed the leads to see if I see a high reading, I was getting the same 0.5 (the BR on the good board was showing about 0.5 and high as expected with the various combinations).

The D1 diode (BYV28-600) close to it was reading 0 both ways (and fell apart when I desoldered it, and I think I can see the fracture line on the original photo). I was seeing about 0.37 and high on the corresponding diode on the good board; is this possibly marginal?

However, when D1 was taken off the board, I retested the bridge rectifier. The AC to + tests were reading 0.5, reversed they went up to 0.8. The AC to - tests gave similar results, 0.5 normal direction, 0.8 reversed.

D1 is (normally) connected between points 1 and 4 of the bridge rectifier.

Does the bridge rectifier sound like it's ok?

Would the bad diode at D1 be causing the blown fuses? Or do I need to look at any other components?