Sometimes I accidently 'flip' On-Off-On the power switch of my TFT LCD, could this cause any harm to the LCD's circuits?

Or the appliance has some protection against this? (my worry is that such on-off flipping cause some surge or arch). It's said that in modern PC LCD monitors like mine (where the power switch is just a touch sensitive area of the front bevel) most of the actual circuitry remains on all the time so I have nothing to worry about, is that correct?

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It should be fine.  The touch-sensitive buttons on most electronics detect changes in capacitance; since there's no mechanical switch, there's nothing to wear out.

As for a power surge, Ork is right.  There's only a danger if the component is "cold".  Since the monitor is technically in standby, there's no real surge.

I will say that while LCD's don't technically "burn in" like CRT's or plasmas, the crystals can develop a memory causing image persistence (which looks almost identical).  I had this issue with my HDTV a few years ago when the phenomenon wasn't well documented; the vertical bars present on 4:3 programs caused a seam whenever 16:9 material was viewed.  I was convinced it was defective because, as I argued to the warranty company, "it's an LCD monitor - there's nothing to burn in!"  I forced them to exchange it, only to find out a few years later what was going on.

Unlike burn-in where the phosphors are worn out, image persistence is reversible in almost all but the most severe cases.  There are programs that either display static or a color negative of the desktop, both of which can be effective.  However, the most success has been reported from those preventing the issue in the first place - by using a blank screensaver and powering the monitor off when not in use.
orksecurity7 years ago
IBM looked into this question. Electronics tends to fail most often when there's a power surge into _cold_ hardware (think about the light bulb that fails when you first turn it on), so this particular scenario isn't likely to do much if any damage. It isn't recommended that you do this _continuously_, but an occasional oops isn't likely to have any statistically significant effect.

They also looked into how the loss of life due to power-on surge compares to the cost of electricity to keep things running. With an old-style CRT, it was very clear that if you're going to live the CRT unused for more than five minutes or so, turning it off is a net cost savings and probably better for the planet. Power-down screensavers are better than nothing, but as you noted there some electronics that stays active so it can power back up again quickly. Other kinds of screensavers are pretty, but pretty useless; they prevent burnin, but not as well as the power-down version... and LCDs are pretty much immune to burn-in. (Plasma can burn in, though it takes a while.)

Yes, I did say CRT in the previous paragraph. I'm pretty sure the study has been redone with LCD screens, but I don't know the results thereof. Given that prices of monitors, including LCDs, has come down so much I'm guessing that the answer remains about the same -- if you're just looking away for a minute or two you can let it run; if you're looking away for ten minutes you may want to let the powersaver kick in;  if you're actually leaving the room it's probably worth physically turning off... and theoretically it's probably worth turning the whole system off overnight, but it's hard to talk people into doing so.

(What some folks do, as a compromise, is to put all the peripherals on a powerstrip, and turn all of them off between PC sessions. That gives you a single switch, and obviously brings them down completely rather than just into sleep mode. Generally it's going to take you longer to find what you want to print out than  for the printer to warm up.)

have you open an tft lcd?do oyu know its defusng plastics proper order,coz i accidentally mix them up and i end up in a no display screen,i was trying to do bchafy project and accidentally disassemble evrything not remembering whats first and whats next,and thus those plastics have something to do wiyh the lcd?
allymcbeal (author)  orksecurity7 years ago
 Thanks for all the answers, guys!  Indeed it was actually the "oops" that happened sometimes.  I asked here about any possible long-term harm because in my country the company's technical support is notoriously awful, right next to useless, and researching the internet I've noticed that several people had problems with the Samsung T220's start button, either becoming unresposible, or switching on and off on its own randomly(!)

Cya all!
It's possible that you could damage the switch itself, but if it's that easy to do accidentally, it's probably already a junky switch.  Anyway, if that happens the repair shouldn't be difficult or expensive.  That's the most I'd worry about.

One other possibility is that a logic circuit could receive unexpected or partial instructions.  It could glitch temporarily, but the odds of it causing any permanent damage are one in a million. 

I wouldn't worry about it, but why don't you try to avoid the problem.  Is there something you can move to avoid brushing against it?
lemonie7 years ago
It should be fine under "sometimes". After all, if they're giving you an on-off button, they have anticipated it being used. (Repeatedly stabbing it might cause a problem)