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Any insight when buying used lcd pc monitor?

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vlad777

Member
I am looking to buy used benq t221wa 22inch monitor because its cheap.
The owner says that only one of menu buttons work, and I saw a picture of it
displaying a picture.

I am going to try it out in different resolutions and refreshes, and check
for dead pixels (before I buy it).

What could this button fault be?
Should I test for something else, and generally what should I be aware of?
Does somebody have experience with this type?

Many thanks.
 
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3v0

Coop Build Coordinator
Forum Supporter
One of the most frequent thing to go on flat screens is the circuitry that drives the backlight. With a used one you have no idea how long it is till that failure. One mode of backlight problems displays the image for seconds or more then cuts out. So seeing a picture of the image is not proof that it is working.

The backlight thing may be less of a problem with LED backlights. Not sure but we have guys that repair them as part of there job and they will know more.

How much less is it then a comparable new one ?

EDIT: I would search online for the model number and find reviews etc to see what people are saying about it.
 
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picbits

Well-Known Member
Quite often the older / more used the screen, the longer the backlight will take to warm up and during this period the screen may have a pink tint or dull yellow tint - if the screen isn't at its best after 20 seconds or so, walk away.
 

BioniC187

Member
That is very low. all my mates lcd's have packed up after 3-4 years. so find out how old the monitor is before conisdering. It would be money well spent to buy a new monitor
 

vlad777

Member
I shared my revelation in this thread:
http://www.electro-tech-online.com/threads/chinese-neon-bulb.114308/
that filament never dies only the driver: specifically filter cap.

So now that you tell me that the problem is ccfl driver, I am glad it's not the tube itself.

So would I be right to think that ccfl driver is something reparable?

@Nigel Average you say is lifespan or price?
 
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vlad777

Member
OK so I bought Asus vw191s, and I got the service manual for free download here:
http://www.eserviceinfo.com/download.php?fileid=61333
http://fileshare.eshop.bg/download.php?fileid=61332

It flickers very faintly, so if I decide to hack it open maybe I learn something. ;)

Edit:

OK so after half an hour or so it started hissing at me and turned off.
Before I try to return it, I'll pry it open. Do you want to see some pics?
Also I think we should devise a strategy or an algorithm for buying
a used lcd monitor.
 
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Nigel Goodwin

Super Moderator
Most Helpful Member
I shared my revelation in this thread:
http://www.electro-tech-online.com/threads/chinese-neon-bulb.114308/
that filament never dies only the driver: specifically filter cap.

So now that you tell me that the problem is ccfl driver, I am glad it's not the tube itself.

So would I be right to think that ccfl driver is something reparable?

@Nigel Average you say is lifespan or price?
Lifespan - a cheap LCD monitor is only likely to last 3-4 years.

Tubes certainly fail in some monitors/TV's - in my TV experience it's almost always Sharp TV's that have problems with CCFL failure, it seems extremely rare in Sony TV's regardless of LCD type fitted.
 

vlad777

Member
This is what I have for now:

Check manufacture date because ccfl only lasts 3-4 years.
Check for scratches.
When your standing take it in your hands and closely look at display surface.
When its cold turn it on and look at color.
Wait to see if it turns off-on after few minutes.
Listen for faint or loud hissing-sparky sound.
Check for faint flicker, give your self a minute.
Check if one side of the screen is uniformly (just a little bit) darker then the other.
Try it in different modes and refreshes.
Check for dead pixels.(white and black jpg in full screen)
Check for smears using pictures on lots of white background.
Smears are visible horizontally after rectangular shapes,
but can be due to faulty vga cable.
If possible try it out for an hour.
 
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