Amp volume knob problem

Jabroni · 7th December 2004, 07:46 AM

Hi all, sorry if this is a newbie question for you. I have an NHT SA-2 mono amp powering an NHT sub. Touching the volume knob makes the sound go extremely loud. Sometimes it will stay loud for awhile before going back to quiet. Usually it just goes back when I take my finger off of it. I sent the amp in to be serviced about a year ago when it quit working, and they fixed this problem then too. The knob also seemed slightly more resistant to turning when I got it back, but that could just be my imagination. But after a short time, it went back to the way it was. Would this just require some cleaning to fix? If so, how would I do it exactly? Thanks!!!

thomas997 · 7th December 2004, 09:47 AM

hm thats odd..

I would try cleaning it first, there could possibly be a bad connection inside the pot. And of course replace it with a similar one if necessary.

It could be that they had replaced the pot when you got it repaired, new ones are usually harder to turn.

Jabroni · 9th December 2004, 07:29 AM

What's the best way to clean it?

hacknet · 9th December 2004, 07:34 AM

philips contact cleaner

Eva · 9th December 2004, 08:17 AM

"The knob also seemed slightly more resistant to turning when I got it back" --> This means they replaced your old potentiometer by a new one

You are probably experiencing a bad solder joint, a broken PCB track or a broken potentiometer track. Strong vibrations, mechanical stress or shocks are the usual causes [usually a shock to the knob]

Sometimes one of the PCB tracks breaks just near its solder joint to the potentiometer [pretty hard to notice at first sight]. However note that in case of a bad solder joint, it may not be one of the legs of the potentiometer, so finding where the contact is lost requires a lot of patience

I do not recommend any contact cleaner for potentiometers, they usually go noisy forever once you have applied any fluid to them and contact cleaners also ruin the mechanically damped soft feeling of the knobs [very frustrating for mixing consoles, not to mention that then the mixing console smells contact cleaner for ever]

If the potentiometer is faulty replace it. There is no remedy for broken potentiometer tracks. In the other hand, dirty or corroded potentiometers produce lots of noise when turning the knob, but dirt is very unlikely to be the causing the problem

7th December 2004, 07:46 AM	#1
Jabroni diyAudio Member Join Date: Dec 2004 Location: usa	Amp volume knob problem Hi all, sorry if this is a newbie question for you. I have an NHT SA-2 mono amp powering an NHT sub. Touching the volume knob makes the sound go extremely loud. Sometimes it will stay loud for awhile before going back to quiet. Usually it just goes back when I take my finger off of it. I sent the amp in to be serviced about a year ago when it quit working, and they fixed this problem then too. The knob also seemed slightly more resistant to turning when I got it back, but that could just be my imagination. But after a short time, it went back to the way it was. Would this just require some cleaning to fix? If so, how would I do it exactly? Thanks!!!

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7th December 2004, 09:47 AM	#2
thomas997 diyAudio Member Join Date: Feb 2004 Location: Vancouver	hm thats odd.. I would try cleaning it first, there could possibly be a bad connection inside the pot. And of course replace it with a similar one if necessary. It could be that they had replaced the pot when you got it repaired, new ones are usually harder to turn.

9th December 2004, 07:29 AM	#3
Jabroni diyAudio Member Join Date: Dec 2004 Location: usa	What's the best way to clean it?

9th December 2004, 07:34 AM	#4
hacknet diyAudio Member Join Date: Nov 2002 Location: sg	philips contact cleaner

9th December 2004, 08:17 AM	#5
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	"The knob also seemed slightly more resistant to turning when I got it back" --> This means they replaced your old potentiometer by a new one You are probably experiencing a bad solder joint, a broken PCB track or a broken potentiometer track. Strong vibrations, mechanical stress or shocks are the usual causes [usually a shock to the knob] Sometimes one of the PCB tracks breaks just near its solder joint to the potentiometer [pretty hard to notice at first sight]. However note that in case of a bad solder joint, it may not be one of the legs of the potentiometer, so finding where the contact is lost requires a lot of patience I do not recommend any contact cleaner for potentiometers, they usually go noisy forever once you have applied any fluid to them and contact cleaners also ruin the mechanically damped soft feeling of the knobs [very frustrating for mixing consoles, not to mention that then the mixing console smells contact cleaner for ever] If the potentiometer is faulty replace it. There is no remedy for broken potentiometer tracks. In the other hand, dirty or corroded potentiometers produce lots of noise when turning the knob, but dirt is very unlikely to be the causing the problem

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