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Old 06-28-2010, 09:29 AM   #1
fred.fw
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Default Philips 190S LCD power problem

Well, i need your help for a Philips 190S5 monitor which don't want to start (but I 've found a special method to turn it on !).
I'm sure the problem comes from the power board (Ambit T50P050) because I tried to swap it with a working power board from another Philips and it works.
The problem with the power board is that when I press the the power button there is no reaction and the led don't light.
But if I keep the power button pressed when the monitor is unplugged from sector and then I plug it, the monitor starts (LED is ON) and it works perfectly. Now if I unplugg it from sector when it works, whenever i will replug into sector it works. But if I stop it with the power button, it will not be possible to turn it on except with the method i described before.

I have replaced all capacitors except the big one 100uF 450V and a small 22uF 50V but the problem is the same.

When it has the problem that it is impossible to turn it on, I have seen with a multimeter that there is 5V, 3,3 V and 12V present on the board and it make a strange noise like cliking noise. The noise disappears when I succeed to turn it on.

Where do you think this problem comes from, please ?
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Old 06-28-2010, 10:34 AM   #2
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Default Re: Philips 190S LCD power problem

clicking noise -> PSU tries to start up but fails for some reason .. repeating it over and over..
try replacing the 22F 50V cap first if everything else works fine (once it turns on).

edit: what brand/series did you replace the original caps with? if they aren't low-esr, the PSU may also fail to start up..
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Last edited by Scenic; 06-28-2010 at 10:39 AM..
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Old 06-28-2010, 11:59 AM   #3
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Default Re: Philips 190S LCD power problem

Thanks for your reply,
Ok I will try to replace the 22F 50V, but now I don't have such capa here.
What's the role of this small capacitor and how do you explain that when I succeed to turn it on, the board will always automatically turn on every time I plug it ?

I forgot to say the board suffered from heat as the color is brown near the transformer.

The caps I replaced are low esr hitano 105.
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Old 06-28-2010, 12:34 PM   #4
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Default Re: Philips 190S LCD power problem

a small cap on the primary side (usually around 50V and below 100F ; 47F is very common) is usually the filter cap for the PWM Controller.

if it dries out or fails otherwise, the powersupply either doesn't start up at all (or only after x tries turning it off and back on), pulses, or does other weird things like for example the problem you've got..

i don't really know about hitano caps. i've read about them on here before, but as i don't have any real-life experience with those, i don't really trust them.

follow the traces from the cap. it should go to a (usually) 8pin chip (the PWM controller).
look up the datasheet for it (for example on alldatasheet.com) and look for the supply voltage (Vcc)..
in some cases, the max. supply voltage is 30V or less, so you could (in theory) use a 35V cap instead of a 50V one. measuring the voltage on that cap can also confirm this.

i did this countless times and replaced 50V 47F caps for the PWM controller with 35V 47F or 56F one's after looking up the datasheet.

i've recently had an LG 19" LCD with a Fairchild FAN7601 PWM Controller that actually had a max. supply voltage of just 20V.. so i replaced the original 50V 39F (? .. strange value) cap with a 25V 47F Panasonic FC..

edit: actual voltage going to that FAN7601 controller was around 18V

Last edited by Scenic; 06-28-2010 at 12:40 PM..
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Old 06-28-2010, 01:33 PM   #5
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Default Re: Philips 190S LCD power problem

Near the small capa, I found a chip NCP1203 (SMD 8 pin) on the backside of the board. It seems to be the PWM as you said. I've read the datasheet and it confirms pin 6 (vcc) is connected to an external bulk capacitor of typically 22F, and VCC is 16V.

When you say the powersupply doesn't start if the filter cap is dead, does it means that there is no voltage produced ? (because I still find 5V and 12V on the board when it doesn't want to start)
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Old 06-28-2010, 02:40 PM   #6
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Default Re: Philips 190S LCD power problem

if it cycles on and off (the clicking sound), the output caps may keep the voltage up within the split second when the PWM controller stops working and tries to restart.

max. supply voltage is 16V, so you could use a 25+V cap instead of the 50V one. 16V would probably be too close..
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Old 06-29-2010, 01:34 PM   #7
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Default Re: Philips 190S LCD power problem

Many thanks for your help Scenic. I will try to change this small cap and I will keep you informed...
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Old 07-08-2010, 12:09 PM   #8
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Default Re: Philips 190S LCD power problem

I've replaced the small cap with a used 22uF 250V that I recovered to test..... and it works perfectly !

Thanks a lot.
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Old 07-08-2010, 03:00 PM   #9
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Default Re: Philips 190S LCD power problem

Personally, I'm a huge Scenic fan.
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Old 08-30-2010, 09:03 AM   #10
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Default Re: Philips 190S LCD power problem

Hey Guys,

I have the same board of you and, I search the value of CMS resistor who had burn . They are unreadable.

the number of the components write on the board is : 3117, 3118, 3115, 3155, 3154

Or if you have the datasheet of the board it will be perfect

Thks a lot
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Old 08-30-2010, 09:57 AM   #11
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Default Re: Philips 190S LCD power problem

I tried to look up that series of numbers but could not find any components assigned to them. Please post a picture of the board and if you could, not the affected area (burned resistors) and based on what part of the circuit this is in, we can locate similar part maybe.
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Old 08-30-2010, 10:19 AM   #12
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Default Re: Philips 190S LCD power problem

its the bottom of the board


img_0157 par emietflo, sur Flickr

Its on upper right hand side of the board

img_0158 par emietflo, sur Flickr

Thx
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Old 08-30-2010, 01:01 PM   #13
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Default Re: Philips 190S LCD power problem

Looks really bad. If you would, post a pic of the topside of this board. I have a feeling that the components on top may have something to do with this type of failure.
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Old 11-04-2010, 12:23 PM   #14
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Default Re: Philips 190S LCD power problem

Hello everyone.
I also have problem with 190S monitor. After I switch it on I works 5 seconds and switch off, after 5 seconds again switch on. And so on. Each 5 seconds it switchs off and in 5 seconds switch on again. Seems that problem also in Power board?

Thanks for helping
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Old 11-04-2010, 12:25 PM   #15
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Default Re: Philips 190S LCD power problem

Quote:
Originally Posted by saprizo View Post
I also have problem with 190S monitor. After I switch it on I works 5 seconds and switch off, after 5 seconds again switch on. And so on. Each 5 seconds it switchs off and in 5 seconds switch on again. Seems that problem also in Power board?
Take it apart and see if you have obviously bloated or swollen caps.
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Old 11-05-2010, 02:08 AM   #16
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Default Re: Philips 190S LCD power problem

Thanks,

Will try to do that.
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Old 11-05-2010, 07:45 AM   #17
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Default Re: Philips 190S LCD power problem

Quote:
Originally Posted by saprizo View Post
Hello everyone.
I also have problem with 190S monitor. After I switch it on I works 5 seconds and switch off, after 5 seconds again switch on. And so on. Each 5 seconds it switchs off and in 5 seconds switch on again. Seems that problem also in Power board?

Thanks for helping

Last night I was working on a monitor that uses the FAN7601 controller. You might want to verify that the capacitor there talking about 50v 47uf is not really a 50v .47uf cap.
I tried using a 50v 1uf in mine and was experiencing a blinking PLED.
For testing I found a 50v .47uf non low esr cap and my monitor came to life .I do have the correct part ordered and will replace it when it comes in.
Al.
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Old 06-14-2011, 04:44 AM   #18
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Default Re: Philips 190S LCD power problem

Hi,
I have the same problem of gredoo, smoked resistors 3154 and 3155.
I can't see original value
Hey gredoo ..did you solved the problem. which was the values? and/or broken componensts.
Does someone has shematic?
(t50p050.00 ambit board)
Thank you if you can help me
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Old 06-24-2011, 07:08 AM   #19
aleksandar kocev
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Default Re: Philips 190S LCD power problem

philips monitor model 190 S , yelow line in right part of monitor how to fix this problem .
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Old 06-24-2011, 10:50 AM   #20
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Default Re: Philips 190S LCD power problem

Quote:
Originally Posted by aleksandar kocev View Post
philips monitor model 190 S , yelow line in right part of monitor how to fix this problem .
Replace the LCD panel.

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