[access-uk] Unstable Volume Controls

  • From: "Darren Brewer" <darren.m.brewer@xxxxxxxxxxxxxxxx>
  • To: <access-uk@xxxxxxxxxxxxx>
  • Date: Fri, 23 May 2008 14:11:48 +0100

Hi All

I seem to remember that a week or so ago somebody posted a message about their 
volume level going up and down by itself.

Well I've had the same annoying problem for a while now and although I knew 
what the problem might be down to I just never got around to fixing it. 
However, yesterday I finally thought it was about time to do something.

My speaker system is the Creative I trigue 2200 which has two small speakers 
and a base unit which everything plugs into. There is a separate volume control 
which plugs into the bass unit. This control has a large knob for altering the 
volume and a small thumb wheel to vary the bass.  

I was a bit apprehensive about opening up the volume control unit as it didn't 
have any screws to undo and I didn't want to damage it as it would render the 
speakers useless.  Often with volume knobs there is a small screw in the side 
that holds the knob onto the potentiometer shaft, but this wasn't the case. 
Instead I just pulled the knob up and it came off together with a small plastic 
ring that clips into place. Luckily nothing broke and I was able to gain access 
to it's insides.

Having worked as an electronics designer I knew that the volume is controlled 
by something called a potentiometer or variable resistor.  These are what you 
turn when you alter the volume on a lot of hifi equipment. They are vary simple 
in how they work, but because you have two surfaces in contact, one of which 
moves over the other when you turn the dial, they can get a bit dirty, or 
grease can build up which interferes with the contact.

These components come in two types, linear or logarithmic. You can tell one 
type from another because with linear volume controls the volume increases 
steadily as you turn the dial. In a linear fashion. So turning the volume half 
way would increase it by half. However with logarithmic controls, the volume 
increases much more rapidly. Both types work in the same way. As you turn the 
dial one piece of copper is moved across another piece, this either increases 
or decreases the electrical resistance, which in turn increases or decreases 
the volume level.

So if you get a volume control that crackles or jumps or even varies up and 
down by itself. Then it probably has some dirt inside. the simple solution is 
to spray a cleaner of some sort inside the actual component itself. I happened 
to have some WD40 and this worked a treat.  The volume level can now be varied 
exactly and it doesn't change by itself anymore.

Obviously if you are going to do anything like this you must disconnect the 
device from the mains and only use a little cleaner. WD40 does the job, but PCB 
cleaner, available from Maplin would also do the trick.

I don't know if the person who posted has the same problem I did, but if they 
try this it might just fix it.

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