Volume Pot cleaning Spray

[Adrian Jansen]

:
:Joe G (Home) wrote:
:> Hi All,
:>
:> I am look for some to purchase the magic volume pot cleaning spray.
:>
:> What do you recommend?
:>
:> and Where to get in Melb?
:>
:> Thanks in advance.
:>
:> Joe
:>
:>
:If its an audio control, and its 'crackly' that is a sign that its
:getting DC current through it. So its well worth checking any
:capacitors around the pot, and ensure they are not leaking DC current.
:Old electros are well known to do this. And after you replace the
:electros, you may still have to replace the pot to get rid of the noise.

Adrian, I note the "design engineer" tag on your post but you don't seem to be
aware of why pots get "crackly". Inside a potentiometer there is a wiper which
makes contact with the resistive element and every time you move the wiper it
attempts to dislodge some of the resistive material. The more oftern the wiper
is moved the more material gets dislodged. It is these dislodged particles of
resistive material which cause the noise in 99% of cases. It is NOT necessarily
(in fact, rarely ever) because they have DC flowing through them.

High quality pots such as Alps etc are costly because they made to resist (no
pun intended) the dislodging of material. That's one reason they are expensive.

I know how a pot is made, thanks. But in servicing many dozens of audio
mixer desks and similar gear, I had much experience with pots and their
problems. In almost all cases I ever found, 'crackly' noise could be
traced to DC current through the pot - not much current - even a few uA
is enough to cause problems. Of course there are plenty of other
failure modes too, but this one stands out as being very common. I must
admit I dont know exactly what causes the 'crackles', and its true that
removing the DC will stop it recurring, but I mostly found that I had to
replace the pot too. Certainly modern pots are better than the old
carbon track ones, but until the OP says what his pot actually is, and
even whether this is the problem, then we are all guessing.

--
Regards,

Adrian Jansen adrianjansen at internode dot on dot net
Design Engineer J & K Micro Systems
Microcomputer solutions for industrial control
Note reply address is invalid, convert address above to machine form.

 

[Phil Allison]

"Adrian Jansen"

I know how a pot is made, thanks.

** A very doubtful claim.

But in servicing many dozens of audio mixer desks and similar gear, I had
much experience with pots and their problems. In almost all cases I ever
found, 'crackly' noise could be traced to DC current through the pot

** I service audio mixing desks all the time - been doing so since the
70s - noisy pots and faders are a very common problem, as are noisy
switches.

However, the noise problem is NOT due to DC leakage current since this is
damn near impossible - cos the inputs AND outputs of audio op-amps are at
ZERO VOLTS DC !!!!!

- not much current - even a few uA is enough to cause problems.

** That issue is SO rare I cannot recall a single example in the last 10
years.

Only an antique audio desk using a single DC supply rail instead of dual +/-
rails could be involved.

Of course there are plenty of other failure modes too, but this one stands
out as being very common.

** This is patently 100% FALSE !!

I must admit I dont know exactly what causes the 'crackles', and its true
that removing the DC will stop it recurring, but I mostly found that I had
to replace the pot too.

** Complete drivel.

A simple cleaning operation fixes over 99% of all noisy pots, faders and
switches.

Certainly modern pots are better than the old carbon track ones,

** How ridiculous is this getting ????

Modern pots and faders still use carbon tracks - at least 99.99 % of them
do. High quality faders may use conductive plastic tracks for long life -
but even they can still become quite noisy and need cleaning from time to
time.

but until the OP says what his pot actually is, and even whether this is
the problem, then we are all guessing.

** What is 100% clear is that YOU are BULLSHITTTING like crazy.

Noisy pots are easily fixed by using a bit of spray lubricant, since the
problem is normally just a small amount of gunk adhering to the wiper.

Anyone tech who does not know that is a complete FOOL !!

Anyone who routinely replaces noisy pots and faders instead of simply
cleaning them is a CROOK.



...... Phil

 

[Eeyore]

"Adrian Jansen"


** A very doubtful claim.


** I service audio mixing desks all the time - been doing so since the
70s - noisy pots and faders are a very common problem, as are noisy
switches.

However, the noise problem is NOT due to DC leakage current since this is
damn near impossible - cos the inputs AND outputs of audio op-amps are at
ZERO VOLTS DC !!!!!

Ever heard of input bias current ? Not every design places a cap in the way.

Graham

 

[Phil Allison]

"Eeysore Fuckwit Anencephalic Pommy "

Ever heard of input bias current ?

** Not one tiny bit relevant to the subject of leaky coupling electros
making pots noisy.

You fucking autistic retard.



....... Phil

 

[RMD]

Hi All,

I am look for some to purchase the magic volume pot cleaning spray.

What do you recommend?

and Where to get in Melb?

Thanks in advance.

Joe

This will have all the ranting anti-WD40 idiots out in droves, but as
Phil says a bit of WD40 usually _permanently_ (as in for many years
into the future) cures noisy volume controls.

It is the first thing I would try, assuming the spray can enter the
pot. If it doesn't work then very little is lost since you will either
have to put up with noise or find a replacement pot and do a
change-over.

Changing out pots can be a nightmare on some equipment.

I'd rather burn it down instead and claim the insurance.

Ross

 

[Eeyore]

"Eeysore Fuckwit Anencephalic Pommy "


** Not one tiny bit relevant to the subject of leaky coupling electros
making pots noisy.

It's ANOTHER current source or sink.

Graham