Wharfedale LTF37K1CB Picture problem

[tom66]

Re: Wharfedale LTF37K1CB Picture problem

20V is much too low. 23V to 26V range on the 24V line.

[Smokin House]

Re: Wharfedale LTF37K1CB Picture problem

Yep. While it was running fine after 1st turning on but after turning off and then on again (then the screen lights went out again) it went up.

I thought that it was 20v because of power drain?

[tom66]

Re: Wharfedale LTF37K1CB Picture problem

Only 20V on the inverter connections?

[Smokin House]

Re: Wharfedale LTF37K1CB Picture problem

Ok I'm back with more info and readings.

Got a digi multimeter, set to 200 DCV.

Have not had the telly on since I last wrote here.

Turned TV on and it stayed on, left it for over an hour and it was fine.

Voltages to the inverter are as follows for when it was running from start and just before I turned the TV off an hour later.
All voltages were taken while the TV was on and working

top white (marked VBR on the board) - steady 4.3v
bottom white (marked on/off on the board) - fluctuating between 3.7v & 3.8v
ALL 5 red wires (marked 24v on board) - steady 20.1v

After the hour I thought 'ok lets turn the set off for 15 mins', so proceeded to do so. Waited. Then turned back on.

Straight back to the way it was before no picture but have sound.
So I checked the voltages again with no picture.

top white (marked VBR on the board) - steady 4.4v
bottom white (marked on/off on the board) - steady 3.8
ALL 5 red wires (marked 24v on board) - fluctuating 24.7v & 24.8v

I hope this will help someone fathom my problem out.

[Smokin House]

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.

Thanks Tom. Hmmmm £20 from maplins or £4 from ebay. Looks like I will wait a couple of days. Will post back once arrived and tested again.

ps. Thanks for all the help so far guys. I really appreciate it!!

[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.

[Smokin House]

Re: Wharfedale LTF37K1CB Picture problem

unfortunately yes that is all I have

[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

"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

[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.

[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.

[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

[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

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

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

[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?

[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.

[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.

[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.

[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.