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raf
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Hum & static from amp

I have an NAD 7150 integrated amp (circa 1983) feeding Boston Acoustics A150 speakers (same age). The amp has a phono output, but there is no phono connected. When the "listen" knob on the amp is turned to phono, I get a loud hum from the left speaker. Any idea what might be causing it?

Also, I get a bit of static-like noise when turning the volume knob (from both speakers). Again, any idea as to cause?

Thanks for your help.

Jan Vigne
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Re: Hum & static from amp

Patient: Doctor, it hurts when I do this.

Doctor: Don't do that.

The phono input wants a turntable connected to it. If you don't have a turntable, don't turn the switch to phono and don't worry about it.

The VC is dirty. It happens after 20+ years. The fix is to clean the control. I don't remember if the NAD used sealed potentiometers or not. Probably. The best solution would be to have a tech go over the unit to check for any other age related problems and to do a thorough cleaing of all connectors, switches and pots. General maintenance type stuff that you might as well do once every twenty years.

Pull the grills off your speakers and check the foam surrounds on the woofers. After this amount of time, I'm surprised the surrounds have not fallen apart. Cut the ends off your speaker cables and strip the insulation back to the point where you will have nice shiny copper to insert into the speaker connectors of your cleaned up amp. Better yet, buy some new speaker cable and interconnects. The RCA connectors on your interconnects have also oxidized and should be replaced since you can't easily clean them. Ask the tech about any particular problems you should be aware of with a twenty four year old amp. He'll explain about capacitors and how they age and what they sound like when they go bad.

jackfish
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Re: Hum & static from amp

The first is most likely a loose connection in the phone section of the amp. The second is a dirty volume pot. You can get spray on contact cleaner for cleaning the pots on the controls.

Elk
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Re: Hum & static from amp

Radio Shack sells the spray cleaner that you need to clean the volume control. I have an ancient Technics receiver that had the same problem.

Jan Vigne
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Re: Hum & static from amp

rafortuno, even if I could buy a can of spray cleaner for $0.02, I would still take the amp to a shop. They can make the RCA's on the back of the amp shine! They can check the amp for specs and then check the caps and resistors should the amp not be up to spec. Crimmennny, guy, you spent a few hundred bucks twenty years ago, give the amp some tender lovin'care at this point, it's only right. You wouldn't run your car without a check up for twenty years; would you? Take the amp to a specialist.

raf
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Joined: Jul 21 2007 - 1:46pm
Re: Hum & static from amp

Thanks to everyone who responded. My concern was whether these were fixable problems or signs of an impending fatal breakdown, and all of you clarified that. The receiver is now at the repair shop.

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