Viewsonic N3260W 32" LCD TV - Dark picture & flickering

[Markie76]

Hi Guys,

I have been given a Viewsonic N3260W 32 inch LCD tv which powers up ok but it has the following picture fault;

1. The screen comes on but it is dark; left half is darker than the right half - which is still below 'normal' brightness.

2. The whole screen flickers - it seems like the backlight is flickering quite quickly - the best way to describe it is like a flourescent tube light which is on its way out or having trouble igniting.

Please view the video below to see the issue;
http://youtu.be/kv3T3_iXV7Y

Your ideas and suggestions welcome.

I can post more pictures/do tests this weekend.

Thank for reading.

[tom66]

Re: Viewsonic N3260W 32" LCD TV - Dark picture & flickering

Before the problem occurred, would it go away after warming up or running for some time, or only occur after running for some time?

To me, it looks like the 24V from the power supply is low. Common causes of this are bad PFC capacitor or non functioning PFC, but bad 24V or inverter capacitors can cause this too.

A good start is taking the set apart and posting pictures.

Do you own a digital multimeter (DMM)?

[Markie76]

Re: Viewsonic N3260W 32" LCD TV - Dark picture & flickering

HI Tom,

Thank you for your reply.

I was given this set and don't know the history.

I do have a multimeter and am able to disassemble and post pics.

What would you like to see and what should I measure?


Thanks.

[tom66]

Re: Viewsonic N3260W 32" LCD TV - Dark picture & flickering

One picture of the whole chassis, and one of each easily accessible board will do for now. Then I can highlight testing points.

[Markie76]

Re: Viewsonic N3260W 32" LCD TV - Dark picture & flickering

Aha! Under the PSU heatspreaders were hiding some bulging and 'rising above the sleeve' caps!!!

Pictures attached;
1. Chassis
2. PSU
3. Cap closeup
4. Logic board
5. LCD chassis
6. Inverter
7. Inverter & Panel part numbers.

The full size pictures available here;
http://i1122.photobucket.com/albums/...psd0a5ff31.jpg
http://i1122.photobucket.com/albums/...psc5fd5f9d.jpg
http://i1122.photobucket.com/albums/...pscc8b060d.jpg
http://i1122.photobucket.com/albums/...ps4d18737b.jpg
http://i1122.photobucket.com/albums/...psf18283b6.jpg
http://i1122.photobucket.com/albums/...ps4429b03d.jpg

[tom66]

Re: Viewsonic N3260W 32" LCD TV - Dark picture & flickering

Bingo. Bad caps. Replace ALL the secondary caps, in my opinion.
While you are at it, test the voltage across that large, blue 450V capacitor. Expecting around 380 to 410V DC.

[Mrx3750]

Re: Viewsonic N3260W 32" LCD TV - Dark picture & flickering

Oh yeah. You have bulged caps, and caps that have seen a lot of heat. Like Tom66 said, replace all the secondary caps, even if they aren't bulged. (the big filter cap should be okay)

[Markie76]

Re: Viewsonic N3260W 32" LCD TV - Dark picture & flickering

Ok. When you say 'secondary caps' - do you mean all 7 big ones in the close up pic or ALL CAPS in the top part of the PSU?

The big blue cap;
On standby: 343.1v
Powered on: 389.6v

I'll update once caps are replaced.

Thanks.

[tom66]

Re: Viewsonic N3260W 32" LCD TV - Dark picture & flickering

You live in a country with 240V mains?
The blue cap is fine.
Secondary caps are the ones to the left of the three yellow transformers, such as those two bulged ones. I would recommend replacing at least all of the CAPXON branded ones, as they are probably the worst capacitors ever made.

[Mrx3750]

Re: Viewsonic N3260W 32" LCD TV - Dark picture & flickering

For a quick visual reference on where to start, see the attached pic.

Replace all the capacitors in the area I circled.

You may also want to replace the small capacitors just above the circle.

[Markie76]

Re: Viewsonic N3260W 32" LCD TV - Dark picture & flickering

For a quick visual reference on where to start, see the attached pic.

Replace all the capacitors in the area I circled.

You may also want to replace the small capacitors just above the circle.

You live in a country with 240V mains?
The blue cap is fine.
Secondary caps are the ones to the left of the three yellow transformers, such as those two bulged ones. I would recommend replacing at least all of the CAPXON branded ones, as they are probably the worst capacitors ever made.

Sorry for the delay in responding - for some reason I had thought I posted an update but I was wrong

Thank you both for your replies and advice.

Yes I am in the UK and we did have 240v mains but at some point the UK Government agreed to harmonization at 230V although 240v sounds more impressive

I replaced all the capacitors to the left of the three transformers - the circled ones and ones above...and the tv seems absolutely fine now!!

Mother has been using it since December and I think I've even managed to move her over to widescreen 16:9 format

Thanks for your help.

Mark.

[tom66]

Re: Viewsonic N3260W 32" LCD TV - Dark picture & flickering

As a note, the UK mains voltage is unchanged from 240V. Would be rather expensive to swap over thousands of transformers. But the definition moved from 240V(-10/+5%) to 230V±10% (or something close to that.) All to bring the paperwork into line with EU standards, whilst actually changing nothing -- aren't standards bodies wonderful...

Enjoy the TV.