Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

**tom66** · 05-17-2013, 05:18 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

If you get no 5VSB, the output diode may have failed, or, more likely, since the fuse was blown, the controller IC for the 5VSB may be bad. As far as testing the LCD panel, you can power up the inverters with a 24V, ~150W power supply (minimum.)

**Daize** · 05-17-2013, 05:30 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Originally posted by tom66

If you get no 5VSB, the output diode may have failed, or, more likely, since the fuse was blown, the controller IC for the 5VSB may be bad. As far as testing the LCD panel, you can power up the inverters with a 24V, ~150W power supply (minimum.)

Could the 5VSB controller IC be U101 (near the two big caps)? How would you suggest testing it (if possible)?

The printing on U101 is "DM311 VE51", I couldn't find a sheet for it. The output diodes seem to test okay, I'm not certain though.

**tom66** · 05-17-2013, 05:45 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Is there an "MLTxxx" number on this power supply? I have more than 1,500 schematics for LCD power supplies. There may be a match.

**budm** · 05-17-2013, 08:41 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

The board has PFC voltage booster, so at standby you should have about 230Vac (or what ever your line voltage is) x 1.414 = DC voltage on the two legs of that large filter cap. Also when you are working in the Primary (hot side) of the circuit, the negative leg of the large cap will be the ground ref. point when you are making any DC voltage reading in the primary side. The chassis ground is the ground ref. point for the isolated secondary side (cold side of the circuit).
So please verify the voltage you have on that large cap.
That is Megmeet power supply, so I hope you have the diagram for it Tom.

**Daize** · 05-17-2013, 05:58 PM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Alas, I had a bit of an 'issue' with it. I replaced the second large cap for the fun of it (the one that looked fine) and fed the board some AC and an entire trace vaporised along with several SMD resistors in it's path. A lovely light show that knocked out the AC circuit's breaker (10a) but not the slow-blow on the board

.

I can fix the trace and replace the resistors, but then I'm stuck looking for the cause and then the likely possibility that I've fried other components.

I decided I'd take the risk that the TV was only thrown out because of the power board failure, so I have bought a new board from a dodgy-looking Taobao site for ~$30. Probably take about a month to arrive from China... Could I have bought it cheaper elsewhere?

Yes, it is indeed a Megmeet MLT083. I would still very much appreciate a copy of the schematics if you have this one, Tom. Thank you.

I might play with bench powering it in the meantime, if I can hunt down a 24v power supply with >6a. I only have a temperamental power supply that only goes up to 12v. The panel and controller would only be <12v, wouldn't it?

EDIT: Thank you Tom and Budm for your suggestions, by the way!

EDIT 2: Haha, I only just realised this has EEFLs not CCFLs, hence the single wire on each side (this was a concern on my old thread). That's a relief, I'm fairly hopeful a new power board will get this running. The actual LCD panel might still be bad, though...

**tom66** · 05-17-2013, 06:37 PM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

No schematic yet, sorry...
EEFL, are you sure? Never heard of an LCD using electroluminscent backlight, other than a small 2" one in an old camcorder I took apart.

**Daize** · 05-17-2013, 07:06 PM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Originally posted by tom66

No schematic yet, sorry...
EEFL, are you sure? Never heard of an LCD using electroluminscent backlight, other than a small 2" one in an old camcorder I took apart.

Hi Tom, you're thinking of EL backlighting. EEFL is similar to CCFL, but has external electrodes.

See my attached pictures. The EEFL tubes run the length of the screen and are all tied to a single row per side (in parallel). Hence one wire per side. They apparently run cooler than CCFL as well.

Also, see:
http://www.youtube.com/watch?v=UjkqmHte_Qo

http://www.youtube.com/watch?v=qQ9H3lClcdo

Attached Files

**budm** · 05-17-2013, 07:21 PM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Learning something everyday, I myself never run into LCD TV using this kind of lamp yet.
http://www.j-right.com/html/eefl_lamp.htm

**Daize** · 05-17-2013, 07:26 PM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

It's interesting, isn't it? This isn't particularly new technology, but I hadn't come across it in person before either. Apparently most larger LG.Philips panels use EEFLs.

I love CCFLs, I use them for all manner of things. I might see if I can find a spare set of EEFLs to play with them.

**tom66** · 05-18-2013, 04:54 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

I have seen older LG.Philips LCD with one transformer for every two bulbs, so I think those were using CCFLs. I've had those have 2 seconds to black, but only failed transformers being the cause. Otherwise I have "never" seen an LG.Philips LCD with 2 seconds to black in the models with a single wire going into the panel, since all the bulbs are in parallel, it would be difficult to detect a faulty one, and EEFL tends to last longer than CCFL. The more you know...

**Daize** · 05-21-2013, 04:43 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Hi again,
The Chinese seller I'm dealing with is now claiming he doesn't actually have the exact replacement, and he's trying to tell me that the one in the picture attached will work fine and has exactly the same 10-pin header output.

I'm finding this incredibly difficult to believe as I have no confidence in the word of a Chinese seller who may or may not have any understanding of electronics.

Does anyone here recognise this power supply? I can see something that looks like a manufacturer name, but I cannot find anything about it. Can anyone at least recognise the manufacturer logo?

On my power supply (Megmeet MLT083), I simply have this on the 10-pin header in order:
+5vsb, P-On, +V2, GND, GND, GND, GND, +V1, +V1, +V1
All grounds are tied, all +V1 are tied

Does anyone know what voltages +v1 and +v2 are? I presume +V1 is 24vdc and +V2 is 12vdc. Does that sound right? If so, the blurry photo of this supposed "good substitute" looks like it may line up but even so, what is the likelihood of it not being able to supply enough current?

If it cannot supply enough current the set should only either shut down randomly or not be able to even start, correct? No damage should occur?

Alternatively, if it is rated for a higher current it should only supply what the equipment pulls shouldn't it? So again it shouldn't damage anything?

I need to give this seller a very prompt reply (I am hoping that there is a possibility it will work as I don't like my chances of seeing a cent returned), and so I would really appreciate anyone's words on this (I'm happy with just opinions, I'm not going to hold you responsible if it doesn't work

)

Yes, I know I should get what I bought, but I really don't like negotiating with Chinese online sellers, they can be ruthless. I've done that before and ended up with no money, no item. I'll either try the supply or go all-out to get my money back, but I don't want to change my demand part-way though so I'd love any opinions on the power supply. It was cheap, only about $32.

Thanks again!

EDIT: This is the actual item I bought - http://item.taobao.com/item.htm?id=18209339674
Of course I only machine translated it, I know Japanese not Chinese haha, and I missed the part where it says "alternative"...

Have a look here. I don't think this is exactly the same, but it looks like this is common in China to replace with "universal" power supplies. Do repair centres use these elsewhere?
http://translate.google.com.au/trans...rticleID%3D334

Attached Files

**tom66** · 05-21-2013, 04:53 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

No way the backlight current (8A) is going to go through two flimsy AWG26 wires; it won't work. Those are rated for, maybe 1A? 1.5A?

**Daize** · 05-21-2013, 05:02 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Yes, I didn't like that, either. I figured if the pins on the male header are connected I could possibly add extra wires. It's claiming it's 6a on the 24v.

I think I found it. The manufacturer is "Skyvin".

Can I possibly use this? I'm sorry, I still am not sure on the specs for the original power supply. No amount of 'googling' has found it yet unless I'm trying the wrong things/places.

The TV uses an LG.Philips 37" LCD panel with EEFLs. It has a very cheap-looking mainboard which I doubt has a high power consumption. I don't have the entire television's wattage rating on hand, I can update later. I think it was about 130w at 240vac.

This is the "universal" replacement:
http://www.aliexpress.com/store/prod...628242293.html

EDIT: I don't get the wiring bundle shown in that link's photograph. I get the tiny harness you see in the first attached picture.

**Daize** · 05-21-2013, 05:15 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Arg! Just to make it worse I have found other ones that look -very- similar from Skyvin but have different ratings!

So far, they have all claimed higher amperage though (different models, same layout).

EDIT: More information here:
http://hslcd.com/Article_Show.asp?ArticleID=334

**Clydeuk** · 05-21-2013, 05:20 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Any chance of some close-up photo's of the vaporised trace etc?

**Daize** · 05-21-2013, 05:23 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Originally posted by Clydeuk

Any chance of some close-up photo's of the vaporised trace etc?

Certainly, I'll pop some up tomorrow when I get home. I may be able to a bit later. It wasn't as dramatic as I made it sound, but at the moment I don't really want to fix it. I may try to fix it when I have more time, but I'm guessing I've damaged even more components on it now.

I really need some more suggestions or opinions on this possible replacement Skyvin board, though.

**tom66** · 05-21-2013, 05:32 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

I wouldn't trust a Skyvin board; I've never seen them in TVs. Whilst Megmeet et al are not good power supplies they are at least capable of putting out their rated power (until a cap bloats or a FET fries.)

**Daize** · 05-21-2013, 05:32 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Also, allegedly EEFL backlights use less power than CCFL. Perhaps 6a may be enough? Thoughts?

Should the 5v and 12v amperage be enough perhaps?

**tom66** · 05-21-2013, 05:34 AM

Re: Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

24V @ 6A = 144W

Mainboard plus audio is usually 5W continuous, 15W peak (loud sound etc.)
T-con/Panel pulls around 10~15W.

So it may be capable, but I would be skeptical.

Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

Konka KLC-TM3718 - AC in, no DC out - all caps, fuses, diodes, rectifier fine

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