Sign in with
Sign up | Sign in
Your question

Power issues with Big LCD in small village

Last response: in Components
Share
July 25, 2012 4:34:16 PM

I am working in a small village with a laptop computer and a high-end NEC LCD monitor for film and photo editing that is having trouble coping with irregularities in the local power supply... :pfff:  when you have stopped laughing maybe you can give me some advice?

The main problem I am facing is that my LCD monitor crashes whenever there is a spike in the power supply, even though my whole system is running through a fairly powerful APC UPS. At first I thought the problem with the LCD was overheating so I moved the whole system in to an air-conditioned room to see if this would prevent the crashing. It did not. However it brought to my attention the problem with the spike in the power supply that I was able to notice because of the air-conditioning system. Every time there was a spike in the power supply the roar of the air-conditioning system changed pitch and every time that happened the LCD monitor crashed - even though the LCD was hooked up via the UPS. I tried a different UPS but it did not make any difference.

So what I have learned so far is that a UPS is not good enough protection to stop surges in the power supply crashing my system.

Now I think I have found the problem I am not sure what to do next?

Probably the best thing to do would be to rewire the building but that is not an option.

Is there some type of portable spike/surge supressing device that I could get to solve this problem, and if there is should it be connected before or after the UPS?

I would prefer not to throw my LCD into the sea - even though it is probably not made for use in such conditions.
a b ) Power supply
July 25, 2012 5:01:30 PM

A UPS will protect the LCD from power surges just because of the way it works, but it is not surge protection in itself. It is possible that the constant power surges has damaged the UPS, so every time a surge happens, it cuts power to the LCD. I would recommend getting a surge protector and hooking it up between the power source and the UPS. I think a lot of power bars come with surge protection.
a b ) Power supply
July 25, 2012 5:20:20 PM

Adding more surge suppression won't help a device that is excessively sensitive to changes in supply voltage. For those cases, online-UPS might be the only official option.

I would call the manufacturer and ask about whether or not the LCD can accept 170VDC or 350VDC input. If it can, I would simply put together a heavily filtered AC-DC bridge rectifier and hook the display to that to supplement the display PSU's own 100uF capacitor.

Another somewhat more risky possibility would be to take the display apart and beef up its input capacitor if there is enough space for that.
Related resources
July 25, 2012 5:28:20 PM

Thanks for the suggestion chairman Ray. To test it I switched the UPS off and on at the wall socket to see if the LCD would crash or not. It didn't crash - the UPS switched over to battery and the LCD didn't even blink, so as far as I can see the UPS is not damaged so bad that it cuts power to the LCD whenever there is a surge. Could it be that as you say the "constant surges has just damaged the UPS's surge protector (if it was any good in the first place).

Another thing is I already have the LCD connected to the UPS via a power bar that has some sort of built in surge protecter but once again probably not a very good quality one.
July 25, 2012 5:46:43 PM

"a device that is excessively sensitive to changes in supply voltage"

I think this hits the nail right on the head. Here is a link to the specs of my "NEC22" Widescreen Professional Graphics Desktop Monitor":

http://www.necdisplay.com/p/desktop%20-monitors/p221w-b...

What do you think? Maybe makes more sense to drive a roadster through a mangrove swamp than trying to use this outside of a normal office environment?

Now I will look up the rectifier you mention to try and find out what that does.

Another concern is if the power supply has this effect on my LCD maybe it is best to stick with a laptop and not even think about hooking up the Intel i7 600W desktop system that I use for video editing... at least not until this problem is solved
July 25, 2012 5:48:59 PM

btw is it possible that power surges have damaged the LCD making it even more sensitive to surges than it would normally be?
a b ) Power supply
July 25, 2012 8:07:36 PM

lowep said:
Now I will look up the rectifier you mention to try and find out what that does.

The principle is simple: switching PSUs used by tons of electronics these days use diodes to take the 120Vac and turn it into raw DC so it can be filtered/stored by input capacitors and used by the HF transformer primary-side switches. Depending on how the LCD screen PSU is wired to do this, it may (or not) be compatible with pre-processing AC to DC before the LCD's input and may (or not) require voltage doubling, hence the need to check either with the manufacturer or though reverse-engineering.

Since this is non-standard operation, the necessary specifications to determine whether or not something is compatible with pre-processed rectified AC are almost never provided by manufacturers.
!