Dell 1800PF Video Flashes Then Stabilizes

**WNG** · 06-19-2007, 02:19 PM

Re: Dell 1800PF Video Flashes Then Stabilizes

Can you post some pics?

I have the same flat panel, two of them, with one with a detectable flicker, like the refresh rate on a CRT not high enough. Does this regardless of DVI or VGA input.

Does your's flash when using either input?

**starfury1** · 06-19-2007, 08:38 PM

Re: Dell 1800PF Video Flashes Then Stabilizes

You say it stops and is OK after 15min?

if you switch it of for a minute or two does it cam back on and stay on?

Does it completely die as in looks like no power?

The reason I ask is that the psu is probably the best heat source in there and it Sounds like a heat sensitive fault of some kind either a component but more likely some sort of contact or solder joint problem

Or it may just be unable to keep the picture steady until some component comes up to temp or up to frequency.

Thats the point it shouldn't so yeah a heat sensitive component is a possibility

Yes some fault with the inverter is a possibility also, they do tend to fail alot
with these types of monitors.

As to the caps...I don't know
Your inverter board is probably a different model
companies just make inverter boards for others to use

sometimes there can be problems with video connectors especially if they are being plugged unplugged a lot but that would happen anytime and doubt this is the case since there seems to be a constant 15 min window on it.

I am assuming it was working ok for some period of time.

just as a side point on a bit of searching I found that it appears to be very close to ( if not maybe the same) as this model LG Flatron L1810B.
How accurate that is I dont know

hopefully someone that fixes these things will give you better advice.

**printone2** · 06-19-2007, 09:34 PM

Re: Dell 1800PF Video Flashes Then Stabilizes

Originally posted by WNG

Can you post some pics?

I have the same flat panel, two of them, with one with a detectable flicker, like the refresh rate on a CRT not high enough. Does this regardless of DVI or VGA input.

Does your's flash when using either input?

Sorry, I do not have a DVI source. Mine does not really flicker like a refresh issue. This LCD goes blank for a second then stays on for a second.

**printone2** · 06-19-2007, 09:54 PM

Re: Dell 1800PF Video Flashes Then Stabilizes

Originally posted by starfury1

You say it stops and is OK after 15min?

if you switch it of for a minute or two does it cam back on and stay on?

I did switch it on and off, but not for a minute or two. When I turn it back on after it has warmed up it appears to act normally.

Does it completely die as in looks like no power?

The reason I ask is that the psu is probably the best heat source in there and it Sounds like a heat sensitive fault of some kind either a component but more likely some sort of contact or solder joint problem

Thats the point it shouldn't so yeah a heat sensitive component is a possibility

Yes some fault with the inverter is a possibility also, they do tend to fail alot
with these types of monitors.

As to the caps...I don't know
Your inverter board is probably a different model
companies just make inverter boards for others to use

sometimes there can be problems with video connectors especially if they are
being plugged unplugged a lot but that would happen anytime and doubt this is the case since there seems to be a constant 15 min window on it.

I am assuming it was working ok for some period of time.

just as a side point on a bit of searching I found that it appears to be very close to ( if not maybe the same) as this model LG Flatron L1810B.
How accurate that is I dont know

hopefully someone that fixes these things will give you better advice.

Here is a link to the what the inverter looks like: http://www.lcdrepair.us/1800inverterKUBNKM045A.html

I left the monitor on for three hours today. It got very hot, but displayed a good picture after it warmed up during the first 15 minutes. This really seems strange that it is able to take all the heat. I would assume that it would fail when the components got hot. I suppose that when a connection gets warm that the connection expands and makes better contact.

After it gets warm there is no sign of any flicker or abnormal video. I had been under the impression that this panel was using the same inverter as the Gateway FPD1830, which has a problem with (4) 100uf 25v caps. This 1800FP does not have those caps, so I am looking for a way to focus the problem down to the PSU, AD or inverter.

I did test the psu with a digital multimeter, with the lcd plugged in, but not turned on. It tested two leads with 12v and two with 5v. How can I test the different boards if all I have is a Fluke 70 III DMM? Thanks.

**starfury1** · 06-20-2007, 05:58 AM

Re: Dell 1800PF Video Flashes Then Stabilizes

the big problem is its intermittent and heat related by the looks of it so unless its a common type problem it could prove hard to track down.

That is what I was thinking once it warms up you have expansion making the contact better.

The easiest way is to switch system blocks like change inverter psu etc but to do that you would need one working same model...that you probably don't have.

Thanks for the link and the inverter you have is different type but same job.
from the link I see the other and it has the 4 caps on it so thats probably the one you are referring to.

I dont fix these (well the ones I fixed were different)

what you can try is re seat connectors and give the the boards a good visual with a jewels loupe or good mag glass this for solder joints,components (solder joints as well)
you can try the hot and cold type trick. (freezer spray hairdryer etc)

I asked if when it went blank was it like it had turned off cause I was trying to see if it maybe an intermittent fault with the PSU (from what I gather these psu's fail a lot)

being a good source of heat there is a good chance it may have developed a dry joint on the pcb, sometimes components that are bolted to heatsinks through contraction and expansion will hairline crack the solder joint very had to see sometimes too.

The shot gun approached is to reflow all solder joints that maybe susceptible to this.

People do with time and experience working on particular models
get very good a being able to tell which area the problems in from the symptoms

Unfortunately I am not one of them in this case. so yeah could be any of the 3 but i am thinking most likely is PSU

Hopefully someone here who does fix em on a day to day basis can give you better advice.

HTH anyway

Cheers

**kc8adu** · 06-20-2007, 06:09 AM

Re: Dell 1800PF Video Flashes Then Stabilizes

being ok after warmup sounds like dried out caps.
seeing a lot of them in lcd's
esp the sm type.i now replace with sm tantalums.

**printone2** · 06-20-2007, 08:24 AM

Re: Dell 1800PF Video Flashes Then Stabilizes

Making some progress. I sectioned off the psu, video and inverter and heated them up with a hair dryer. I seems that the inverter is the problem. I can heat it up or cool it with a fan and can duplicate the problem.

Now if I can just analyze the inverter's issue.

**printone2** · 06-20-2007, 09:53 AM

Re: Dell 1800PF Video Flashes Then Stabilizes

I have narrowed it down to top half of the inverter board. I also found a site that shows a replacement board and indicates that if the monitor flashes on and off for 1/2 to several seconds that the inverter board should be replaced.
http://www.lcdparts.net/InverterDeta...6633TZA015AMSS

I have looked for a cooked part or a fractured solder joint, but could not find any. The soldering is mostly surface mount and of course very tiny for my hands. I do not know how to narrow my search any closer, and am willing to hear suggestions. The shield covers the inverter during normal operation and I do not think that the other parts will work normally with the shield removed.

**printone2** · 06-20-2007, 11:59 AM

Re: Dell 1800PF Video Flashes Then Stabilizes

I had a professional resolder the top half of the board, but that did not make it any better or worse. Unless someone can direct me to a specific component that might have failed. I will need to buy a replacement board.

**printone2** · 06-20-2007, 12:32 PM

Re: Dell 1800PF Video Flashes Then Stabilizes

Does being able to duplicate the problem by adding heat or cooling the inverter eliminate the possibility of a bad capacitor? Does it confirm that it must be a cold solder joint?

**kc8adu** · 06-20-2007, 05:29 PM

Re: Dell 1800PF Video Flashes Then Stabilizes

just shotgun all the lytics

**printone2** · 06-20-2007, 07:08 PM

Re: Dell 1800PF Video Flashes Then Stabilizes

Pardon my ignorance, but what specifically does all the lytics include? Does that mean just reflow anything that I can see? My soldering skills may not be quite up to this delicate bit of work.

**starfury1** · 06-20-2007, 07:55 PM

Re: Dell 1800PF Video Flashes Then Stabilizes

Thanks KC8

.......so the inverter strikes again....

faulty components , this case Capacitors are your problem (most likely) and need to be replace
They may look perfectly ok but they are not

from what you have found the inverter is the problem you can either replace it or as KC8adu
said, you need to replace all the Electrolytic capacitors on the pcb smc type and any others there
There are (if that first pcb is the same as yours) 2 normal type electrolytic's there as well from what I can tell

if you don't have the tools or skill then just replace the pcb

surface mount capacitors look like this Here but some are black as well...they will be larger and have a + symbol on them

its up to your which way you go.

HTH

Dell 1800PF Video Flashes Then Stabilizes

Dell 1800PF Video Flashes Then Stabilizes

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