LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

[ukagwx]

Hello All,
The LCD Monitor Sceptre x20wg-naga will go black after 1-2 sec. If I turn on
the monitor the screen just stay for few seconds, and then goes away(black)
but power is on. If I turn off and then turn on,the screen come back and goes black again for 1 to 2 sec.
I checked board with power supply and inverter, and found the Capacitor C101(25v 150uf) is bad, I replaced that caps and tested that, but problem is not solved on this way.
I have searched this forum and got so many good guidance how to fix this problem. But I am new to electronics repair and don't have experience for the repair. I hope I can get detailed help from this forum for this monitor.

Thanks in advance.

Because the uploading is failed, I try post links for pics of power board. Sorry
for the inconvenience.
http://weather1.ca.uky.edu/lcd/IMG_0299.JPG
http://weather1.ca.uky.edu/lcd/IMG_0308.JPG
http://weather1.ca.uky.edu/lcd/IMG_0309.JPG
http://weather1.ca.uky.edu/lcd/IMG_0310.JPG

[PlainBill]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

Typical description of 'two seconds to black'. If you found one bad cap there is no reason to believe the other caps are good. They can (and do) fail with no visible signs.

Did you use a good quality low ESR cap as a replacement? General purpose caps will not work properly; even after a complete recap using new general purpose caps a monitor can exhibit this problem.

The two most common causes of 'two seconds to black' are bad caps (40%), bad (aged) CCFLs or a problem with the CCFL wiring (40%), bad transformer (15%), bad component in the protection circuitry (5%).

If you have a good CCFL (or a non-working monitor with good CCFLs) you can substitute a test CCFL for each CCFL in turn and isolate the problem.

PlainBill

[ukagwx]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

Thanks PlainBill for the quick reply.
I posted pics links on the post.

I see some burned area on the board, this could be a problem?
The transform looks bad? How to check that?

[PlainBill]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

Sorry, I don't download pictures hosted offsite. I'm not sure why you are having problems. Are they less than 2000 x 2000 pixels? Did you try to use 'Manage Attachments' (below the text entry area) to attach them?

PlainBill

[ukagwx]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

Detailed burn area.

On pic IMG_03121.jpg, the right one is burned compare to link one.

[ukagwx]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

I used 'Manage Attachments' to upload the pics, but uploading to 92% and then failed.
I tried many times. All pics are jpg,2.3M to 2.8M. Is this size to big to upload?

[ipman]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

I see nothing wrong with the burned area. And the weirdest thing is that on the other side there is allmost nothing.

Transformers can be checked while not powered with an ohm-meter, they should all give allmost same readings on primary and secondary windings.

Do you have an ESR meter and a DMM?

[ukagwx]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

No,I don't have an ESR meter and a DMM.

[ipman]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

Visually, I cannot identify anything wrong there.
Go get (or borrow/loan) at least a cheap DMM to check voltages. Ideally an ESR-meter also.
I know, tools can be very expensive and it's hard to invest such amount of money to use them now and then. Usually they worth tens or more times than the repaired device, but if you are serious about repairing electronics, you should get at least basic ones.

[ukagwx]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

I am trying uploading pics...

https://www.badcaps.net/forum/attach...1&d=1311699377

https://www.badcaps.net/forum/attach...1&d=1311699377

Uploading is done. The size must be less 2000 x 2000.

[ukagwx]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

More Pics. Burned area.

[ukagwx]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

I will get a DMM right now. How to check and find the problem? Could you mark that
on the pics? Thanks.

[ukagwx]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

Hello ipman,PlainBill or anyone, could you help me to check transformer(like PlanBill ponted:bad transformer (15%)),I post one more pic here.
I am really appreciated your help. better draw/mark that on the pic.

[ukagwx]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

I forgot to say I got a DMM now.

[Rtech]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

Not that transformer......measure resistance(ohms), on the secondaries of the two inverter transformers ....

[ipman]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

The ones near the CCFL connectors, one of them has "QC OK" on it. Secondary means the winding leading to connectors.

[tmcw]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

Have you checked the voltages at the white connector CN001?

If the voltages are bad there, it may prevent the inverter portion from firing up.

I would check for the 5V and 12V in the first instance.

[ukagwx]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

Hi Rtech,ipman and tmcw,
I checked resistance for the two inverter transformers,that shows 621 and 626.
I guess this is Ok(under 3%),right?

But I didn't check CN001 yet.


Look CN001 on pic:


N/F BL 12V GND 5V
. . . . . . .

Is that right?

[ukagwx]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

For the CN001, I checked 5v, got 4.96, no 12v connection(see pic,just 6 connections,blue line).

[Deniz]

Re: LCD Monitor Sceptre x20wg-naga will go black after 1 sec.

How can I buy CN001