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-   -   Philips 190S LCD power problem (http://www.badcaps.net/forum/showthread.php?t=10183)

alnoth 07-14-2011 03:07 AM

Re: Philips 190S LCD power problem
 
my monitor yellow led indicates it is ON, but the screen is blank. when i turn it OFF and back ON, the screen flicks on for an instant and goes to blank again - the monitor is still ON, the led light indicates it is ON, but the screen is blank.

the computer works fine, when i turn the monitor OFF and ON and get the instant on-off blick, the screen shows my desktop and all. which i suppose means, that the cables and the signals got through to the monitor fine. (both power and comp cable are screwed in)

PlainBill 07-14-2011 07:53 AM

Re: Philips 190S LCD power problem
 
Quote:

Originally Posted by alnoth (Post 174983)
my monitor yellow led indicates it is ON, but the screen is blank. when i turn it OFF and back ON, the screen flicks on for an instant and goes to blank again - the monitor is still ON, the led light indicates it is ON, but the screen is blank.

the computer works fine, when i turn the monitor OFF and ON and get the instant on-off blick, the screen shows my desktop and all. which i suppose means, that the cables and the signals got through to the monitor fine. (both power and comp cable are screwed in)

An excellent description of 'Two seconds to black'. It could be due to bad caps, bad inverter transformer, bad CCFLs or CCFL wiring. The first step is to open the monitor up and take good focused pictures of the power supply board. Pictures close to 2000 x 2000 pixels, well lit, from directly above are best. No need for a lot of pictures, one of the top, one of the bottom are sufficient. Attach them using 'Manage Attachments' - below the text entry area.

PlainBill

alnoth 07-14-2011 12:54 PM

Re: Philips 190S LCD power problem
 
i have no idea how to take the damn thing apart. any help will be appreciated, before i put an axe to it...

alnoth 07-14-2011 01:06 PM

Re: Philips 190S LCD power problem
 
never mind the last post, will put up some pics in a while

alnoth 07-14-2011 02:37 PM

Re: Philips 190S LCD power problem
 
2 Attachment(s)
heres the two pics from either side of the board...

PlainBill 07-14-2011 03:01 PM

Re: Philips 190S LCD power problem
 
1 Attachment(s)
Quote:

Originally Posted by alnoth (Post 175030)
heres the two pics from either side of the board...

Thank you. Good, clear pictures, and the problem is obvious. We've had to deal with ao many fuzzy, poorly lit pictures lately it's a pleasure to have something good to work with.

I've circled 7 electrolytic caps in red. All of those are failing and must be replaced. The two caps circled in yellow should also be replaced. In particular, the smaller one will fail without any visible sign and you will have a non-working monitor. There may also be one under the blob of glue I've marked with the red '?'. If there is a cap under there, it should also be replaced.

I recommend Panasonic FM, FR, or FC caps. There are other name brands that also make high quality low ESR caps. If you are in the USA, these will cost about $10 from Digikey, including USPS First Class Mail shipping. I always suggest specifying your location in your profile; it makes it easier to recommend a source of parts.

PlainBill

alnoth 07-14-2011 11:18 PM

Re: Philips 190S LCD power problem
 
thanks for identifying the problem...

i am living in prague, but thats no issue. i have contacts in the states, that can ship over here the small parts i would specify - if i decide to go down that road.

thing is, i have 0 experience soldering and no equipment for the job. so to do it myself, it would cost me near the price of a new screen with dubious results expected. if we were talking about 10 bucks total investments, i would be willing to mess around with it myself.

i will google around to find out prices here in prague, including the repair - not sure i will find a place where they would do it for me (after having not much luck finding a place that would solder a broken ps/2 keyboard connector to my motherboard).

bioray 07-15-2011 01:34 PM

Re: Philips 190S LCD power problem
 
I have been given a freebe monitor. With all freebe's come problems. My display will turn on for 4 seconds but then the backlights turn off. I can see the icons on the desktop with a flashlight. I would think it is an inverter problem. What does the board think????:usa:

jetadm123 07-15-2011 01:45 PM

Re: Philips 190S LCD power problem
 
Quote:

Originally Posted by bioray (Post 175203)
I have been given a freebe monitor. With all freebe's come problems. My display will turn on for 4 seconds but then the backlights turn off. I can see the icons on the desktop with a flashlight. I would think it is an inverter problem. What does the board think????:usa:

Please post some photos of YOUR power board. If it looks like the board in post #25, then it's going to need new caps.

PlainBill 07-15-2011 01:47 PM

Re: Philips 190S LCD power problem
 
Quote:

Originally Posted by bioray (Post 175203)
I have been given a freebe monitor. With all freebe's come problems. My display will turn on for 4 seconds but then the backlights turn off. I can see the icons on the desktop with a flashlight. I would think it is an inverter problem. What does the board think????:usa:

The board doesn't think, it's made of wood. :facepalm:

There is about a 25% chance you are right. The odds are about 35% it's bad caps and 30% it's CCFLs or wiring to the CCFLs. (You don't want to know about the remaining 10%).

Standard suggestion: Take it apart. Take clear, high resolution (2000 x 2000 pixels) pictures of the top and bottom of the power supply. Attach them to your next post using 'Manage Attachments' - below the text entry area.

PlainBill

joeh 07-28-2011 08:25 AM

Re: Philips 190S LCD power problem
 
@plainbill
I've the same problem exposed by alnoth "two seconds to black" and I've already replaced all the electrolityc caps present on the power mainboart, 2 of that was seriously brocken, but result is the same.
Can You help me??
Thanks a lot

PlainBill 07-28-2011 10:55 AM

Re: Philips 190S LCD power problem
 
1 Attachment(s)
Quote:

Originally Posted by joeh (Post 177498)
@plainbill
I've the same problem exposed by alnoth "two seconds to black" and I've already replaced all the electrolityc caps present on the power mainboart, 2 of that was seriously brocken, but result is the same.
Can You help me??
Thanks a lot

1. What brand and series of capacitors did you use for the replacements?

2. I have attached a photo of the bottom of alnoth's power supply. On your power supply, what is the resistance between the two points circled in orange? What is the resistance between the two points circled in yellow?

3. One at a time, substitute a known good CCFL for those in the LCD panel. If the panel works properly when replacing a particular CCFL, that CCFL or the wiring to it is bad.

PlainBill

joeh 07-29-2011 10:40 AM

Re: Philips 190S LCD power problem
 
3 Attachment(s)
Quote:

Originally Posted by PlainBill (Post 177514)
1. What brand and series of capacitors did you use for the replacements?

2. I have attached a photo of the bottom of alnoth's power supply. On your power supply, what is the resistance between the two points circled in orange? What is the resistance between the two points circled in yellow?

3. One at a time, substitute a known good CCFL for those in the LCD panel. If the panel works properly when replacing a particular CCFL, that CCFL or the wiring to it is bad.

PlainBill

Hi Bill excuse me but my pcb is all different, can you help me?
The capacitor are commercial oem capacitor but for me this is not the problem because whit other monitors that i have just repared its works good.
This is my pcb

PlainBill 07-29-2011 11:09 AM

Re: Philips 190S LCD power problem
 
Quote:

Originally Posted by joeh (Post 177669)
Hi Bill excuse me but my pcb is all different, can you help me?
The capacitor are commercial oem capacitor but for me this is not the problem because whit other monitors that i have just repared its works good.
This is my pcb

Refer to the picture of the back of the power supply board. Going from top to bottom, the pins of the secondaries of the inverter transformers are numbered 7 and 12. Measure the resistance between 7 and 12 on the upper transformer and report the resistance. Do the same for the lower transformer. They should match to within 3%.

PlainBill

joeh 07-29-2011 11:37 AM

Re: Philips 190S LCD power problem
 
Tested with a digital tester in the resisance mode
7-12 up .... it says 1. (bad functionality?)
7-12 down...it says .549

I test the points in 20 kohm scale

7-12 up....no ohm
7-12 down.... 0.52 ohm

PlainBill 07-29-2011 03:53 PM

Re: Philips 190S LCD power problem
 
Quote:

Originally Posted by joeh (Post 177677)
Tested with a digital tester in the resisance mode
7-12 up .... it says 1. (bad functionality?)
7-12 down...it says .549

I test the points in 20 kohm scale

7-12 up....no ohm
7-12 down.... 0.52 ohm

Remove the up transformer and verify. It appears you have a bad transformer.

PlainBill

joeh 07-29-2011 04:39 PM

Re: Philips 190S LCD power problem
 
Quote:

Originally Posted by PlainBill (Post 177706)
Remove the up transformer and verify. It appears you have a bad transformer.

PlainBill

How can i test it?
what type of replacement can i sell'
thanks

PlainBill 07-29-2011 08:05 PM

Re: Philips 190S LCD power problem
 
Quote:

Originally Posted by joeh (Post 177709)
How can i test it?
what type of replacement can i sell'
thanks

You test it with an ohmmeter. Measure the resistance between the two leads that were at 7 and 12. As far as a replacement, what numbers are on the transformer? Google them.

PlainBill

joeh 07-30-2011 02:05 AM

Re: Philips 190S LCD power problem
 
it says 0 ohm
i beleave that it's dead can you confirm?

PlainBill 07-30-2011 06:25 AM

Re: Philips 190S LCD power problem
 
Quote:

Originally Posted by joeh (Post 177765)
it says 0 ohm
i beleave that it's dead can you confirm?

No, that means you are measuring it wrong. This is a case where one picture can save many hours. Take a picture of the bottom of the transformer and attach it.

PlainBill


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