Q. once in a while my computer monitor starts making a clicking noise and the screen flickers when it is shut down for a while and i turn it back on it works fine does anyone know what causes this and what you can do to fix it
A. What kind of computer monitor ? Is it a CRT (the old kind of monitor) or is it LCD (the thin flat-screen) ?
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In the CRT type
There is a relay that degausses the tube (applies a varying magnetic field to erase any residual magnetism). This relay is supposed to turn on only when the power is turned on, then turn off shortly afterward and not turn on again. If there is a problem with the power control circuit it might be turning that relay on, which turns on the degaussing coil. If it is clicking then the circuit is going bad, turning the relay on and off.
Another type of clicking noise can be caused by the input circuitry being unable to keep track of the "scan rate" which determines the resolution of the image on the screen. When the circuit changes resolution there is a loud click. If this control circuit is going bad you would hear clicking.
CRTs have high-voltage power supplies for the picture tube; if the transformer is going bad there might be clicking, but usually it buzzes.
When you turn off the monitor the power supply still has power in its capacitors and as those discharge the circuit going bad behaves erratically and causes screen flicker.
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In LCDs you do not have degaussing coils. But the monitor still has circuits that detect the scan rate to display the correct image; if the circuits are going bad it might be making a clicking noise.
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Put the monitor on another computer and see if it still clicks.
If the monitor does not click, your video card or circuits in the computer to be suspected as going bad, sending out bad video signals.
If the monitor does click, you will need to get the monitor repaired or replaced. Repairing monitors is sometimes not worth the trouble; the technician might have to get a service manual for it and then have to get parts. I have been told the Chinese manufacturers are not very helpful with supplying manuals, and parts might be difficult to get. A new monitor is often much cheaper than trying to get it fixed; you can't get much of a warranty on a repair job on old monitors, while you do get a warranty on new monitors.
===== Edit:
I suggest you take it back to the store as it should still be under warranty. Even if the manufacturer's warranty has expired, the store should still maintain the merchandise.
TonyRB
Friday, January 8, 2010
=====
In the CRT type
There is a relay that degausses the tube (applies a varying magnetic field to erase any residual magnetism). This relay is supposed to turn on only when the power is turned on, then turn off shortly afterward and not turn on again. If there is a problem with the power control circuit it might be turning that relay on, which turns on the degaussing coil. If it is clicking then the circuit is going bad, turning the relay on and off.
Another type of clicking noise can be caused by the input circuitry being unable to keep track of the "scan rate" which determines the resolution of the image on the screen. When the circuit changes resolution there is a loud click. If this control circuit is going bad you would hear clicking.
CRTs have high-voltage power supplies for the picture tube; if the transformer is going bad there might be clicking, but usually it buzzes.
When you turn off the monitor the power supply still has power in its capacitors and as those discharge the circuit going bad behaves erratically and causes screen flicker.
=====
In LCDs you do not have degaussing coils. But the monitor still has circuits that detect the scan rate to display the correct image; if the circuits are going bad it might be making a clicking noise.
=====
Put the monitor on another computer and see if it still clicks.
If the monitor does not click, your video card or circuits in the computer to be suspected as going bad, sending out bad video signals.
If the monitor does click, you will need to get the monitor repaired or replaced. Repairing monitors is sometimes not worth the trouble; the technician might have to get a service manual for it and then have to get parts. I have been told the Chinese manufacturers are not very helpful with supplying manuals, and parts might be difficult to get. A new monitor is often much cheaper than trying to get it fixed; you can't get much of a warranty on a repair job on old monitors, while you do get a warranty on new monitors.
===== Edit:
I suggest you take it back to the store as it should still be under warranty. Even if the manufacturer's warranty has expired, the store should still maintain the merchandise.
TonyRB
Friday, January 8, 2010
Importance of HDMI on a computer monitor?
Q. "You have been asked to help edit video for a friend. You have a great notebook computer, which is powerful enough to handle this type of task, but you need to buy a separate LCD monitor to hook up to your computer and are not exactly sure what to buy. You know it should be larger than 17", capable of displaying HD"
The question is: Why or why not would HDMI capability be important.
The question is: Why or why not would HDMI capability be important.
A. HDMI is not especially "important". The two best connections for high quality digital video are DisplayPort (a miniaturized version is Mini DisplayPort) and HDMI. DisplayPort has more than twice the bandwidth at 21.6 Gbit/s (17.28 Gbit/s with overhead removed) as opposed to HDMI's 10.2 Gbit/s (8.16 Gbit/s with overhead removed). It also has the ability to share this bandwidth with multiple streams of audio and video to separate devices.
HDMI is, of course, the preferred connection over VGA, because HDMI is digital, supports higher resolution, and supports audio. The same applies to DisplayPort over VGA.
Many PC makers were very late to get off the VGA bandwagon and get on the digital video express. They first adopted DVI, but it cannot feed multimedia, so now most of them are sucked in to HDMI, just because the major television makers use it.
Computer makers must pay huge royalties to use the HDMI standard and to use the logo. The HDMI Founders are Hitachi, Matsushita Electric Industrial (Panasonic/National/Quasar), Philips, Silicon Image, Sony, Thomson, RCA and Toshiba. All of these founders, except Silicon Image, are major television makers with HDMI port as their choice, no surprise.
DisplayPort / Mini DisplayPort was developed by the Video Electronics Standards Association (VESA), an international standards organization, that charges no royalties for use. Although it is less expensive (royalty-free) and higher bandwidth, it is being ignored by 99% of home computer makers. Only Apple is supporting Mini DisplayPort on their computers to any large degree.
Mini DisplyPort also has the advantage of providing Thunderbolt support with no need for an additional port.
Summary:
Use DisplayPort if the display has both HDMI and DisplayPort, and the computer has DisplayPort (no matter if the computer also has HDMI). The same logic would apply to a drive case. If both the case and the computer have Firewire, don't use USB, because FW is full-duplex, not processor intensive, and has wider bandwidth than USB. (Do not confuse data rate with bandwidth. The theoretical maximum data rate cannot be reached with USB due to the three limitations just outlined.)
<0-0>
HDMI is, of course, the preferred connection over VGA, because HDMI is digital, supports higher resolution, and supports audio. The same applies to DisplayPort over VGA.
Many PC makers were very late to get off the VGA bandwagon and get on the digital video express. They first adopted DVI, but it cannot feed multimedia, so now most of them are sucked in to HDMI, just because the major television makers use it.
Computer makers must pay huge royalties to use the HDMI standard and to use the logo. The HDMI Founders are Hitachi, Matsushita Electric Industrial (Panasonic/National/Quasar), Philips, Silicon Image, Sony, Thomson, RCA and Toshiba. All of these founders, except Silicon Image, are major television makers with HDMI port as their choice, no surprise.
DisplayPort / Mini DisplayPort was developed by the Video Electronics Standards Association (VESA), an international standards organization, that charges no royalties for use. Although it is less expensive (royalty-free) and higher bandwidth, it is being ignored by 99% of home computer makers. Only Apple is supporting Mini DisplayPort on their computers to any large degree.
Mini DisplyPort also has the advantage of providing Thunderbolt support with no need for an additional port.
Summary:
Use DisplayPort if the display has both HDMI and DisplayPort, and the computer has DisplayPort (no matter if the computer also has HDMI). The same logic would apply to a drive case. If both the case and the computer have Firewire, don't use USB, because FW is full-duplex, not processor intensive, and has wider bandwidth than USB. (Do not confuse data rate with bandwidth. The theoretical maximum data rate cannot be reached with USB due to the three limitations just outlined.)
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