Wharfedale LTF37K1CB Picture problem

[Smokin House]

Hi all,

I've got a problem with the above LCD TV and I am hoping someone can help.

To explain the problem:

Powers on.
Screen powers and can access source to choose HDMI 1
Picture shows and get sound for about half a minute or so then no picture but still have sound.

After research (days of it as there's not much about on that TV) I came to the conclusion it was the inverter board as I am getting a steady 24v on all 5 of the power leads from the power board to the inverter and also getting a steady 3v on the 2 white wires to the inverter.

After replacing the inverter I had it running for about 15 mins and all was well BUT then I powered down the TV to put the shield and the back on, lay it down and thought 'lets check it one more time' so plugged it back in and turned on and the problem started again and keeps happening.

Any ideas on what the problem could be please.

I can supply pics/videos if needed.

Many thanks in advance

[tom66]

Re: Wharfedale LTF37K1CB Picture problem

In a dark room, when the picture goes out, does the screen still glow or does it go off?

[Smokin House]

Re: Wharfedale LTF37K1CB Picture problem

Hi Tom66,

Many thanks for taking the time out to reply.

I get no glow from the screen when the picture goes out.

[tom66]

Re: Wharfedale LTF37K1CB Picture problem

OK, at this point we will require you to remove the cover off the rear of the TV and take a detailed picture of the chassis layout and perhaps one of each board. Then we can indicate where to make tests.

[Smokin House]

Re: Wharfedale LTF37K1CB Picture problem

WHOLE LAY OUT:


POWER BOARD:


INVERTER also shows where I have already tested)


MAIN BOARD:


PICTURE IMAGE BOARD: (well I think that is what it is for)

[budm]

Re: Wharfedale LTF37K1CB Picture problem

Can you please edit your post by not posting the pictures in line? Please use 'Go Advanced' to upload the pictures instead, thank you.

[Smokin House]

Re: Wharfedale LTF37K1CB Picture problem

Can you please edit your post by not posting the pictures in line? Please use 'Go Advanced' to upload the pictures instead, thank you.

I did use the go advanced feature and the only option I saw was the url option not an upload option

Will look at the options again in another browser and if it is there will edit.

[Topcat]

Re: Wharfedale LTF37K1CB Picture problem

inline pics are ok and allowed (some just don't like them, but most don't mind). I did attach them to your post, so they'll be here for future users to learn from. For future reference, a post can not be edited after 90 minutes.

[budm]

Re: Wharfedale LTF37K1CB Picture problem

So when the backlights go out the 3VDC on those two pins still present? I'm beginning to think you may have bad soldering works problem on the lamp assembly or lamp sockets if it uses socket type.

[Smokin House]

Re: Wharfedale LTF37K1CB Picture problem

inline pics are ok and allowed (some just don't like them, but most don't mind). I did attach them to your post, so they'll be here for future users to learn from. For future reference, a post can not be edited after 90 minutes.

Thank you so much Topcat! I will remember that information in future (",)

So when the backlights go out the 3VDC on those two pins still present? I'm beginning to think you may have bad soldering works problem on the lamp assembly or lamp sockets if it uses socket type.

Will double check the voltages.

I don't see why the soldering would go just like that though!

I have spotted a slight bulge of a cap under the right hand shield on the main board that I didn't see at 1st until I took it off for a closer look. It is just to the left of the output wires that lead to the inverter. Possible cause?

The cap is a SAMXON 470u F35v 105c and I did read that brand are quite troublesome?

[tom66]

Re: Wharfedale LTF37K1CB Picture problem

Yes, bad Samwha on the inverter can easily cause your problem.

[Smokin House]

Re: Wharfedale LTF37K1CB Picture problem

Samwha? I said it was a Samxon and it was on the main power board not the inverter.

The inverter in the picture is brand spanking new!

[tom66]

Re: Wharfedale LTF37K1CB Picture problem

Sorry, misread you; Too many bad Samwha I have replaced! I have seen the odd bad Samxon, they aren't great caps.

[Smokin House]

Re: Wharfedale LTF37K1CB Picture problem

Sorry, misread you; Too many bad Samwha I have replaced! I have seen the odd bad Samxon, they aren't great caps.

What caps are going to be best to use if I need to replace them?

Oh and yes the voltages to the inverter are fine when the light goes out.

Also I have noticed something weird on the main power board today.

After powering up to check the voltages I left it on for a few mins after testing once the light went out and found that the power board gets hot on the cold side. I'm sure that's not right.

I have indicated below where it reckons it should get hot and where it DOES get hot.



Also pictured here are the caps

[cheapie]

Re: Wharfedale LTF37K1CB Picture problem

"HOT" and "COLD" refers to voltages, not temperature. As in, don't go touching stuff with your bare hands on the "HOT" side while it's plugged in.

[multimeter]

Re: Wharfedale LTF37K1CB Picture problem

replace the caps with panasonic fm,if those caps were bulged id expect a lot lower voltage than 24v ,those caps feed the supply to the inverter,can you measure the outputs to the inverter?on dc volts/200v on your multimeter.

[Smokin House]

Re: Wharfedale LTF37K1CB Picture problem

"HOT" and "COLD" refers to voltages, not temperature. As in, don't go touching stuff with your bare hands on the "HOT" side while it's plugged in.

Trust me to take it literally! Thank you cheapie

replace the caps with panasonic fm,if those caps were bulged id expect a lot lower voltage than 24v ,those caps feed the supply to the inverter,can you measure the outputs to the inverter?on dc volts/200v on your multimeter.

I tested the voltage where the wires meet the inverter board and it was tested on 50 DCV. (only have 2.5/10/50/250/500 settings on multimeter)

When it comes to a choice of caps.......... oh boy!

I found this page but what ones to go for exactly!????? (please excuse the outside link as couldn't find Panasonic caps on badcaps site)
http://uk.mouser.com/Panasonic/Passi...z0wrk5Z1z0x3xj

[tom66]

Re: Wharfedale LTF37K1CB Picture problem

You are using an analog meter? They are no where near accurate enough.

[Smokin House]

Re: Wharfedale LTF37K1CB Picture problem

unfortunately yes that is all I have

[tom66]

Re: Wharfedale LTF37K1CB Picture problem

A digital meter can be acquired for around £6.99 from Maplins, or from other shops. It is pretty much necessary to use a digital meter for modern electronics which are sensitive to 0.1V drop.