Hi, My NEC MultiSync P1250+ has two symptoms:
1. At start up it emits a high frequency hiss from the back. After it warms up a bit, the noise stops.
2. Intermittently, the picture will blip off for an instant and come right back.
Pleas Help, Thanks.
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Re: NEC P1250+ hisses and scrren blips intermittently
I had the same problem. Your monitor is warning you of failure. The hissing sound is the picture tube powering up. The momentary blank screen is when the power supply for the monitor has become hot. Your monitor is getting ready to quit. My suggestion is to buy a new monitor. To have a tech repair it would be more expensive then buying a new one.
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could be a bad cable or could be the high frequency control is turned up too high and the speaker without the hiss has a blown tweeter (high frequency driver), and you're trying to compensate for the lack of highs on the bad speaker by turning up the high frequency on the EQ, which makes the other speaker hiss.
The hiss is caused by the autooscillation of the internal amplifier. To fix that you will need to install some additional filtering capacitors on the power lines, a high frequency filter at both the input and the output of the amplifier (basically just a 100nF capacitor put in series with a 10ohm resistor between the in/out and the ground) and a new routing of the internal cables. Also check a ground loop on the cables.
Some hiss at high gain settings is normal. If you get objectionable hiss at 1 o'clock settings of gain, that is too high. Electronics has noise that is "statistical" in nature due to physics that we can't get around in design. Most hiss is created in the preamp area and swapping tubes in the first stage might help. By varying the volume controls and observing the level of the hiss, we may be able to analyze the offending staage of amplification. ALso turning up the treble controls will increase the hiss, as it is mostly in the higher pitches.
Hook a graphic equalizer between the piano and speakers, and turn down all sliders above 8 kHz. Since the highest note of a piano is 4186 Hz (4.186 kHz), you'll still hear all the notes but cut the hiss. If the hiss is coming from the speaker's power amplifier (in which case the equalizer won't help), turn down the speaker volume and turn up the piano volume. Live instruments generally need some doctoring to sound good through high-quality stereo equipment, as they only produce a limited range of frequencies whereas good speakers reproduce a lot more - including hiss.
I have the Sony Bravia KDL-46S4100. The high-picthed hiss drives me insane. I have a work around but not a fix. Go into your TV's menu and find BACKLIGHT. Adjust it from 1-9 with the house quiet and find what frequency of the hiss is the least annoying.
Sony Bravia high pitch hiss hissing sound high frequency
hi its definatley an air leak if you have replaced the hoses i suggust the next thing you try is see by tighting the carburrettors nuts that hold it to the manifold as these come lose and **** air do the same with the manifold bolts i suspect you will find them loose if not then change the gaskets one at a time with the cheapest first the carburretors then the manifold you may want to go to your car shop and ask for an air leak spray or they may use some other kind of method but basicly you spray it round the carb/manifold and watch to see where the leak is yates210456