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Default cleaning scratchy [electronics] pots / switches


Picked up an old Kenwood tuner/amp for nowt a couple of days ago - I love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input selector are
used. Despite all the putzing around with vintage kit I've done over the
years, this is the first thing I've had where it seems like the pots and
switches could do with a good clean.

So... does isopropanol work? I've used it on all sorts of other
electronics-related cleaning tasks over the years, but I've seen mixed
reports online about it for use with pots, with some folk saying it's OK
and others saying it'll destroy lubricant inside the mechanism (the
latter does seem like a valid concern, but I'm just not sure if it's
being over-cautious - or if whatever lubricant was used has long since
ceased doing a useful job in this thing anyway) .

What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?

I'm trying to avoid the week's wait it'd need to get some conctact
cleaner shipped here - but if that's the way it has to be, then so be
it :-)

cheers

Jules
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Jules Richardson wrote:
Picked up an old Kenwood tuner/amp for nowt a couple of days ago - I love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input selector are
used. Despite all the putzing around with vintage kit I've done over the
years, this is the first thing I've had where it seems like the pots and
switches could do with a good clean.

So... does isopropanol work? I've used it on all sorts of other
electronics-related cleaning tasks over the years, but I've seen mixed
reports online about it for use with pots, with some folk saying it's OK
and others saying it'll destroy lubricant inside the mechanism (the
latter does seem like a valid concern, but I'm just not sure if it's
being over-cautious - or if whatever lubricant was used has long since
ceased doing a useful job in this thing anyway) .

What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?

I'm trying to avoid the week's wait it'd need to get some conctact
cleaner shipped here - but if that's the way it has to be, then so be
it :-)

Switch cleaner would be better for the pot. The problem may be wear of
the track rather than dirt, though, on an amp of that age. I've seen
pots where the base material has been visible through a gap in the
resistive maerial. For the switch, any contact cleaner should do the
job, just check to make sure the plastic isn't going to be affected by
the IPA.

Crackling on volume controls is often caused by DC leakage through
coupling capacitors, so check those, too.


--
Tciao for Now!

John.
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In article , Huge
scribeth thus
On 2011-03-14, Jules Richardson wrote:

Picked up an old Kenwood tuner/amp for nowt a couple of days ago - I love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input selector are
used. Despite all the putzing around with vintage kit I've done over the
years, this is the first thing I've had where it seems like the pots and
switches could do with a good clean.


Judging by the colour of what came out of the input select switch on my
Arcam Alpha 9, and the results, I can strongly recommend "Deoxit" switch
cleaner. It's rather expensive, though.

Those who followed my "Arcam Input Selector" thread from a couple of
weeks ago might like to know that the Deoxit fixed the switch about
95%. There are now clear, crackle-free positions on the input selector.
Sadly, they don't line up with the detents on the switch. (



Http://www.audioaffair.co.uk/Caig-La...ntact-Cleaner-
Spray/product_1150


19 odd quid a can!. Glad me Servisol which I expect is the same stuff is
around 3 quid..

Course if Russ Andrews was to make this then 500 notes a 10 milli litre
bottle anyone;?..

--
Tony Sayer

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Jules Richardson wrote:
Picked up an old Kenwood tuner/amp for nowt a couple of days ago - I love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input selector are
used. Despite all the putzing around with vintage kit I've done over the
years, this is the first thing I've had where it seems like the pots and
switches could do with a good clean.

So... does isopropanol work? I've used it on all sorts of other
electronics-related cleaning tasks over the years, but I've seen mixed
reports online about it for use with pots, with some folk saying it's OK
and others saying it'll destroy lubricant inside the mechanism (the
latter does seem like a valid concern, but I'm just not sure if it's
being over-cautious - or if whatever lubricant was used has long since
ceased doing a useful job in this thing anyway) .

What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?

I'm trying to avoid the week's wait it'd need to get some conctact
cleaner shipped here - but if that's the way it has to be, then so be
it :-)


get the pukka switch cleaner

cheers

Jules

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In message , John
Rumm writes
On 14/03/2011 17:46, Jules Richardson wrote:

Picked up an old Kenwood tuner/amp for nowt a couple of days ago - I love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input selector are
used. Despite all the putzing around with vintage kit I've done over the
years, this is the first thing I've had where it seems like the pots and
switches could do with a good clean.

So... does isopropanol work? I've used it on all sorts of other
electronics-related cleaning tasks over the years, but I've seen mixed
reports online about it for use with pots, with some folk saying it's OK
and others saying it'll destroy lubricant inside the mechanism (the
latter does seem like a valid concern, but I'm just not sure if it's
being over-cautious - or if whatever lubricant was used has long since
ceased doing a useful job in this thing anyway) .

What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?

I'm trying to avoid the week's wait it'd need to get some conctact
cleaner shipped here - but if that's the way it has to be, then so be
it :-)


I have had this problem on a couple of amps. One I did using proper
contact cleaner, the other (also a Kenwood as it happens) I used WD40.
To be fair the WD40 did the better lasting job it seems!

(squirt into the pot from the back - same for the switch, then work
back and forth repeatedly for a bit)

Quite. WD40 is the sort of thing that any self-respecting d-i-yer
usually has about his/her person. Some pundits roundly condemn it as a
switch and pot cleaner/lubricant, but I find it usually works just fine.
--
Ian


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On Mar 14, 7:23*pm, Ian Jackson
wrote:
In message , John
Rumm writes

On 14/03/2011 17:46, Jules Richardson wrote:


Picked up an old Kenwood tuner/amp for nowt a couple of days ago - I love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input selector are
used. Despite all the putzing around with vintage kit I've done over the
years, this is the first thing I've had where it seems like the pots and
switches could do with a good clean.


So... does isopropanol work? I've used it on all sorts of other
electronics-related cleaning tasks over the years, but I've seen mixed
reports online about it for use with pots, with some folk saying it's OK
and others saying it'll destroy lubricant inside the mechanism (the
latter does seem like a valid concern, but I'm just not sure if it's
being over-cautious - or if whatever lubricant was used has long since
ceased doing a useful job in this thing anyway) .


What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?


I'm trying to avoid the week's wait it'd need to get some conctact
cleaner shipped here - but if that's the way it has to be, then so be
it :-)


I have had this problem on a couple of amps. One I did using proper
contact cleaner, the other (also a Kenwood as it happens) I used WD40.
To be fair the WD40 did the better lasting job it seems!


(squirt into the pot from the back - same for the switch, then work
back and forth repeatedly for a bit)


Quite. WD40 is the sort of thing that any self-respecting d-i-yer
usually has about his/her person. Some pundits roundly condemn it as a
switch and pot cleaner/lubricant, but I find it usually works just fine.
--
Ian


WD40 is an oil, of some description. It's great for repelling water,
and soaking into threads. But it really has no place in electrics.

When I worked in the motor trade, I would despair of people - egged on
by the AA - who thought a spray of WD40 was actually a full service.
In reality, the *proper* job was to keep the HT leads clean, to
prevent moisture settling. Once WD40 had been used, you'd get a layer
of grime, which actively trapped moisture, and made it impossible to
start the car.
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In message
,
Jethro writes
On Mar 14, 7:23*pm, Ian Jackson
wrote:
In message , John
Rumm writes

On 14/03/2011 17:46, Jules Richardson wrote:


Picked up an old Kenwood tuner/amp for nowt a couple of days ago - I love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input selector are
used. Despite all the putzing around with vintage kit I've done over the
years, this is the first thing I've had where it seems like the pots and
switches could do with a good clean.


So... does isopropanol work? I've used it on all sorts of other
electronics-related cleaning tasks over the years, but I've seen mixed
reports online about it for use with pots, with some folk saying it's OK
and others saying it'll destroy lubricant inside the mechanism (the
latter does seem like a valid concern, but I'm just not sure if it's
being over-cautious - or if whatever lubricant was used has long since
ceased doing a useful job in this thing anyway) .


What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?


I'm trying to avoid the week's wait it'd need to get some conctact
cleaner shipped here - but if that's the way it has to be, then so be
it :-)


I have had this problem on a couple of amps. One I did using proper
contact cleaner, the other (also a Kenwood as it happens) I used WD40.
To be fair the WD40 did the better lasting job it seems!


(squirt into the pot from the back - same for the switch, then work
back and forth repeatedly for a bit)


Quite. WD40 is the sort of thing that any self-respecting d-i-yer
usually has about his/her person. Some pundits roundly condemn it as a
switch and pot cleaner/lubricant, but I find it usually works just fine.
--
Ian


WD40 is an oil, of some description. It's great for repelling water,
and soaking into threads. But it really has no place in electrics.

When I worked in the motor trade, I would despair of people - egged on
by the AA - who thought a spray of WD40 was actually a full service.
In reality, the *proper* job was to keep the HT leads clean, to
prevent moisture settling. Once WD40 had been used, you'd get a layer
of grime, which actively trapped moisture, and made it impossible to
start the car.


I would never use WD40 on things like cables (especially HT leads)
unless I could wipe most of it off afterwards. But pot and switch
cleaner/lubricant is a different matter. My tiny Electrolube dispenser
got used up about 40 years ago, and I've been using mainly WD40 ever
since.
--
Ian
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We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Jethro
saying something like:

When I worked in the motor trade, I would despair of people - egged on
by the AA - who thought a spray of WD40 was actually a full service.
In reality, the *proper* job was to keep the HT leads clean, to
prevent moisture settling. Once WD40 had been used, you'd get a layer
of grime, which actively trapped moisture, and made it impossible to
start the car.


And often you'd get deterioration of the leads themselves, through the
WD40 acting as a solvent on the covering. Turned some of them into a
sticky mess, it did.
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On Mar 15, 2:30 pm, Grimly Curmudgeon
wrote:
We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Jethro
saying something like:

When I worked in the motor trade, I would despair of people - egged on
by the AA - who thought a spray of WD40 was actually a full service.
In reality, the *proper* job was to keep the HT leads clean, to
prevent moisture settling. Once WD40 had been used, you'd get a layer
of grime, which actively trapped moisture, and made it impossible to
start the car.


And often you'd get deterioration of the leads themselves, through the
WD40 acting as a solvent on the covering. Turned some of them into a
sticky mess, it did.


I don't seem to have any HT leads.
There's just a tiny spring between the coil and the plug!
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In message on Mon, 14 Mar 2011
17:46:36 +0000 (UTC)
Jules Richardson wrote:


What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?


Don't know what it is these days but RS switchcleaner used to be carbon tet
with a bit of oil added and worked on most things, provided they weren't too
bad. Electrolube was better and worked on virtually everything!

However, it is surprising just how good a job oil on its own can do. I don't
know what they put in 3-in-1 but it is surprisingly effective.

--

Terry


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"Terry Casey" wrote in message ...
In message on Mon, 14 Mar 2011
17:46:36 +0000 (UTC)
Jules Richardson wrote:


What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?


Don't know what it is these days but RS switchcleaner used to be carbon tet
with a bit of oil added and worked on most things, provided they weren't too
bad. Electrolube was better and worked on virtually everything!

However, it is surprising just how good a job oil on its own can do. I don't
know what they put in 3-in-1 but it is surprisingly effective.


Try Colmans mustard. It is (or was) made by the same company as 3in1 and WD40
so it *might* work

--
Graham.

%Profound_observation%


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In message , Graham.
writes

"Terry Casey" wrote in message
...
In message on Mon, 14 Mar 2011
17:46:36 +0000 (UTC)
Jules Richardson wrote:


What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?


Don't know what it is these days but RS switchcleaner used to be carbon tet
with a bit of oil added and worked on most things, provided they weren't too
bad. Electrolube was better and worked on virtually everything!

However, it is surprising just how good a job oil on its own can do. I don't
know what they put in 3-in-1 but it is surprisingly effective.


Try Colmans mustard. It is (or was) made by the same company as 3in1 and WD40
so it *might* work

I was once told I could use mustard (instead of Radweld) to seal car
radiator leaks (big mistake - it didn't work, and it didn't half
stink!), but even I wouldn't try it for fixing noisy pots.
--
Ian
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On 14/03/2011 18:28, John Rumm wrote:
On 14/03/2011 17:46, Jules Richardson wrote:

Picked up an old Kenwood tuner/amp for nowt a couple of days ago - I
love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input selector are
used. Despite all the putzing around with vintage kit I've done over the
years, this is the first thing I've had where it seems like the pots and
switches could do with a good clean.

So... does isopropanol work? I've used it on all sorts of other
electronics-related cleaning tasks over the years, but I've seen mixed
reports online about it for use with pots, with some folk saying it's OK
and others saying it'll destroy lubricant inside the mechanism (the
latter does seem like a valid concern, but I'm just not sure if it's
being over-cautious - or if whatever lubricant was used has long since
ceased doing a useful job in this thing anyway) .

What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?

I'm trying to avoid the week's wait it'd need to get some conctact
cleaner shipped here - but if that's the way it has to be, then so be
it :-)


I have had this problem on a couple of amps. One I did using proper
contact cleaner, the other (also a Kenwood as it happens) I used WD40.
To be fair the WD40 did the better lasting job it seems!

(squirt into the pot from the back - same for the switch, then work
back and forth repeatedly for a bit)


I was in the repair industry for 30 years and the use of WD40 by the
public was great. It used to make a little problem into a big one and
give me lots of work..
Remember WD40 is an insulator. ( that's why it is used on car
ignitions) contact cleaner is not a insulator. it is a cleaner.



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In message , Gary
writes
On 14/03/2011 18:28, John Rumm wrote:
On 14/03/2011 17:46, Jules Richardson wrote:

Picked up an old Kenwood tuner/amp for nowt a couple of days ago - I
love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input selector are
used. Despite all the putzing around with vintage kit I've done over the
years, this is the first thing I've had where it seems like the pots and
switches could do with a good clean.

So... does isopropanol work? I've used it on all sorts of other
electronics-related cleaning tasks over the years, but I've seen mixed
reports online about it for use with pots, with some folk saying it's OK
and others saying it'll destroy lubricant inside the mechanism (the
latter does seem like a valid concern, but I'm just not sure if it's
being over-cautious - or if whatever lubricant was used has long since
ceased doing a useful job in this thing anyway) .

What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?

I'm trying to avoid the week's wait it'd need to get some conctact
cleaner shipped here - but if that's the way it has to be, then so be
it :-)


I have had this problem on a couple of amps. One I did using proper
contact cleaner, the other (also a Kenwood as it happens) I used WD40.
To be fair the WD40 did the better lasting job it seems!

(squirt into the pot from the back - same for the switch, then work
back and forth repeatedly for a bit)


I was in the repair industry for 30 years and the use of WD40 by the
public was great. It used to make a little problem into a big one and
give me lots of work..
Remember WD40 is an insulator. ( that's why it is used on car
ignitions) contact cleaner is not a insulator. it is a cleaner.

Basically an oil

and a good job it is an insulator, can you imagine the effect if it
wasn't and you sprayed a conductive film into e.g. a 1meg pot?




--
geoff
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On Mar 14, 5:46*pm, Jules Richardson
wrote:
Picked up an old Kenwood tuner/amp for nowt a couple of days ago - I love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input selector are
used. Despite all the putzing around with vintage kit I've done over the
years, this is the first thing I've had where it seems like the pots and
switches could do with a good clean.

So... does isopropanol work? I've used it on all sorts of other
electronics-related cleaning tasks over the years, but I've seen mixed
reports online about it for use with pots, with some folk saying it's OK
and others saying it'll destroy lubricant inside the mechanism (the
latter does seem like a valid concern, but I'm just not sure if it's
being over-cautious - or if whatever lubricant was used has long since
ceased doing a useful job in this thing anyway) .

What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?

I'm trying to avoid the week's wait it'd need to get some conctact
cleaner shipped here - but if that's the way it has to be, then so be
it :-)

cheers

Jules



You can use any solvent to clean it. Whether some of them are a good
idea is another matter.
Alcohol and IPA contain water, which conducts & corrodes
WD40 contains white spirit and oil. The iol left behind picks up
grime, making the problem worse later.

There's really no reason to buy proprietary overpriced solvents, all
are available at a fraction the price in unbranded form.

I'd try paraffin first, as it evaporates fully and is relatively
harmless.


NT


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In message
,
Tabby writes
On Mar 14, 5:46*pm, Jules Richardson
wrote:
Picked up an old Kenwood tuner/amp for nowt a couple of days ago - I love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input selector are
used. Despite all the putzing around with vintage kit I've done over the
years, this is the first thing I've had where it seems like the pots and
switches could do with a good clean.

So... does isopropanol work? I've used it on all sorts of other
electronics-related cleaning tasks over the years, but I've seen mixed
reports online about it for use with pots, with some folk saying it's OK
and others saying it'll destroy lubricant inside the mechanism (the
latter does seem like a valid concern, but I'm just not sure if it's
being over-cautious - or if whatever lubricant was used has long since
ceased doing a useful job in this thing anyway) .

What about ipa to clean, followed by a little mineral oil down the pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?

I'm trying to avoid the week's wait it'd need to get some conctact
cleaner shipped here - but if that's the way it has to be, then so be
it :-)

cheers

Jules



You can use any solvent to clean it. Whether some of them are a good
idea is another matter.
Alcohol and IPA contain water, which conducts & corrodes
WD40 contains white spirit and oil. The iol left behind picks up
grime, making the problem worse later.

There's really no reason to buy proprietary overpriced solvents, all
are available at a fraction the price in unbranded form.

I'd try paraffin first, as it evaporates fully and is relatively
harmless.

The main argument against WD40 and the like is that it is a lubricant,
and eventually attracts grot. While this is probably true, surely
purpose-made cleaners things like Electrolube are also lubricants?
--
Ian
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On 18/03/2011 00:17, geoff wrote:
In message , Gary
writes
On 14/03/2011 18:28, John Rumm wrote:
On 14/03/2011 17:46, Jules Richardson wrote:

Picked up an old Kenwood tuner/amp for nowt a couple of days ago -
I love
all that old 70s/80s hi-fi stuff. All seems to be working, but has a
major case of the crackles when the volume control or input
selector are
used. Despite all the putzing around with vintage kit I've done
over the
years, this is the first thing I've had where it seems like the
pots and
switches could do with a good clean.

So... does isopropanol work? I've used it on all sorts of other
electronics-related cleaning tasks over the years, but I've seen mixed
reports online about it for use with pots, with some folk saying
it's OK
and others saying it'll destroy lubricant inside the mechanism (the
latter does seem like a valid concern, but I'm just not sure if it's
being over-cautious - or if whatever lubricant was used has long since
ceased doing a useful job in this thing anyway) .

What about ipa to clean, followed by a little mineral oil down the
pot/
switch stem to work as a contact lubricant? Or is that asking for
trouble, too?

I'm trying to avoid the week's wait it'd need to get some conctact
cleaner shipped here - but if that's the way it has to be, then so be
it :-)

I have had this problem on a couple of amps. One I did using proper
contact cleaner, the other (also a Kenwood as it happens) I used
WD40. To be fair the WD40 did the better lasting job it seems!

(squirt into the pot from the back - same for the switch, then work
back and forth repeatedly for a bit)


I was in the repair industry for 30 years and the use of WD40 by the
public was great. It used to make a little problem into a big one
and give me lots of work..
Remember WD40 is an insulator. ( that's why it is used on car
ignitions) contact cleaner is not a insulator. it is a cleaner.

Basically an oil

and a good job it is an insulator, can you imagine the effect if it
wasn't and you sprayed a conductive film into e.g. a 1meg pot?




I often had the problem. Switches sprayed with WD40 became
intermittent. Sprayed with switch cleaner and they worked.

Same with pots. WD40 made them OC cleaner got them serviceable again.

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Default cleaning scratchy [electronics] pots / switches

On Fri, 18 Mar 2011 10:11:42 +0000, Gary
wrote:

On 18/03/2011 00:17, geoff wrote:
In message , Gary
writes


I was in the repair industry for 30 years and the use of WD40 by the
public was great. It used to make a little problem into a big one
and give me lots of work..
Remember WD40 is an insulator. ( that's why it is used on car
ignitions) contact cleaner is not a insulator. it is a cleaner.

Basically an oil

and a good job it is an insulator, can you imagine the effect if it
wasn't and you sprayed a conductive film into e.g. a 1meg pot?

I often had the problem. Switches sprayed with WD40 became
intermittent. Sprayed with switch cleaner and they worked.

Same with pots. WD40 made them OC cleaner got them serviceable again.



For reference a major component of Servisol 'switch cleaner' is
petroleum distillate, a major component of WD40 is...petroleum
distillate. Of course petroleum distillate can cover a whole range of
products but you get the idea

http://www.farnell.com/datasheets/864997.pdf

http://www.wd40.co.uk/media/adobe/a/..._bulk_MSDS.pdf

I've completely trashed, or temporarily damaged a few pots and
switches over the years with all sorts of 'approved' products.

--
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On Fri, 18 Mar 2011 08:11:53 +0000, Ian Jackson wrote:
The main argument against WD40 and the like is that it is a lubricant,
and eventually attracts grot. While this is probably true, surely
purpose-made cleaners things like Electrolube are also lubricants?


I think the issue with WD40 is that over time it wears away but leaves a
sticky residue behind - and that residue is what attracts crud. I assume
that other lubricants, designed to also be cleaners, are formulated so
that they don't do this.

As an update, I tried some IPA, and that gave a huge improvement - in
fact, it was perfect for a few days. As of this morning I'm suddenly
getting signal drop-out on the left channel, but I suspect this isn't
related to switch/pot contacts. Time to have a nose around inside and
probably re-route some things to determine where exactly the fault's
happening. Wish I had my 'scope and ESR meter with me :-(

(I'm also thinking I might prod the car parts place in town this weekend
- maybe they carry some form of switch cleaner)

cheers

Jules

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On Mar 18, 2:03*pm, Jules Richardson
wrote:
On Fri, 18 Mar 2011 08:11:53 +0000, Ian Jackson wrote:
The main argument against WD40 and the like is that it is a lubricant,
and eventually attracts grot. While this is probably true, surely
purpose-made cleaners things like Electrolube are also lubricants?


I think the issue with WD40 is that over time it wears away but leaves a
sticky residue behind - and that residue is what attracts crud. I assume
that other lubricants, designed to also be cleaners, are formulated so
that they don't do this.


Lubes differ of course, what's in wd40 is a sticky oil better suited
to cars.


As an update, I tried some IPA, and that gave a huge improvement - in
fact, it was perfect for a few days. As of this morning I'm suddenly
getting signal drop-out on the left channel, but I suspect this isn't
related to switch/pot contacts. Time to have a nose around inside and
probably re-route some things to determine where exactly the fault's
happening. Wish I had my 'scope and ESR meter with me :-(

(I'm also thinking I might prod the car parts place in town this weekend
- maybe they carry some form of switch cleaner)

cheers

Jules


I have occasionally seen a volume pot carrying dc, but not wired up
correctly, ie arranged so that any slight poor connection produces a
lot of noise. These can typically be silenced just by connceting the
unconnected pot end to the wiper, or if that cant be done fitting a
fixed R to the wiper and ground or one of the other terminals.


NT


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In message
on Fri, 18 Mar 2011 08:52:07 -0700 (PDT)
Tabby wrote:

I have occasionally seen a volume pot carrying dc, but not wired up
correctly, ie arranged so that any slight poor connection produces a
lot of noise.


What do you mean by 'not wired up correctly'?

Carbon pots carrying DC are much more prone to be noisy.

The change from valves to transistors, with their lower impedance circuitry and
leaky electrolytic coupling capacitors, considerably increased the incidence of
noisy volume controls.

Some can be cleaned easily and give long service before more attention is
required, whereas, if the track is badly worn, relief, if any, is only
temporary, no matter what you use.

In such cases, the only remedy is replacement.

These can typically be silenced just by connceting the
unconnected pot end to the wiper ...


There shouldn't be an unconnected end! The pot will typically be connected
between signal and ground with the output being between the wiper and ground.

Carbon pots carrying DC are much more prone to be noisy.

The change from valves to transistors, with their lower impedance circuitry and
'leaky' electrolytic coupling capacitors, considerably increased the incidence
of noisy volume controls.

Some can be cleaned easily and give long service before more attention is
required, whereas, if the track is badly worn, relief, if any, is only
temporary, no matter what you use.

In such cases, the only remedy is replacement.

... or if that cant be done fitting a fixed R to the wiper and ground or one
of the other terminals.


That will modify the 'law' of the pot and change the wiper position for most
settings. If the track is worn in the area that is most usually used (not
surprising!) moving the operating point to a relatively unused section can
work.

Fine as a diy work around but not worthwhile if a replacement is to hand as
that will give a better guarantee of a long term solution.

--

Terry
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In such cases, the only remedy is replacement.

... or if that cant be done fitting a fixed R to the wiper and ground or one
of the other terminals.


That will modify the 'law' of the pot and change the wiper position for most
settings. If the track is worn in the area that is most usually used (not
surprising!) moving the operating point to a relatively unused section can
work.

Fine as a diy work around but not worthwhile if a replacement is to hand as
that will give a better guarantee of a long term solution.


And do check that the electrolytic cap thats supplying the pot or goes
from the wiper onto the next stage is connected the right way around as
I've come across them connected arse about face sometimes;!...
--
Tony Sayer

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On Mar 18, 4:59*pm, Terry Casey wrote:
In message
on Fri, 18 Mar 2011 08:52:07 -0700 (PDT)
*Tabby wrote:



I have occasionally seen a volume pot carrying dc, but not wired up
correctly, ie arranged so that any slight poor connection produces a
lot of noise.


What do you mean by 'not wired up correctly'?

Carbon pots carrying DC are much more prone to be noisy.

The change from valves to transistors, with their lower impedance circuitry and
leaky electrolytic coupling capacitors, considerably increased the incidence of
noisy volume controls.

Some can be cleaned easily and give long service before more attention is
required, whereas, if the track is badly worn, relief, if any, is only
temporary, no matter what you use.

In such cases, the only remedy is replacement.

These can typically be silenced just by connceting the
unconnected pot end to the wiper ...


There shouldn't be an unconnected end! The pot will typically be connected
between signal and ground with the output being between the wiper and ground.

Carbon pots carrying DC are much more prone to be noisy.

The change from valves to transistors, with their lower impedance circuitry and
'leaky' electrolytic coupling capacitors, considerably increased the incidence
of noisy volume controls.

Some can be cleaned easily and give long service before more attention is
required, whereas, if the track is badly worn, relief, if any, is only
temporary, no matter what you use.

In such cases, the only remedy is replacement.

*... or if that cant be done fitting a fixed R to the wiper and ground or one
of the other terminals.


That will modify the 'law' of the pot and change the wiper position for most
settings. If the track is worn in the area that is most usually used (not
surprising!) moving the operating point to a relatively unused section can
work.

Fine as a diy work around but not worthwhile if a replacement is to hand as
that will give a better guarantee of a long term solution.



I wasnt quite clear was I. Sometimes the pot is wired such that if the
wiper goes oc, the output, which connects to the wiper, is o/c. Adding
a fixed R across the pot's output prevents this, ie from wiper to
ground end. It can be high enough value to have only a trivial effect
on the 'law' of the pot, which is a fairly trivial matter anyhow.


NT
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In message
,
Tabby writes
On Mar 18, 4:59*pm, Terry Casey wrote:
In message

on Fri, 18 Mar 2011 08:52:07 -0700 (PDT)
*Tabby wrote:



I have occasionally seen a volume pot carrying dc, but not wired up
correctly, ie arranged so that any slight poor connection produces a
lot of noise.


What do you mean by 'not wired up correctly'?

Carbon pots carrying DC are much more prone to be noisy.

The change from valves to transistors, with their lower impedance
circuitry and
leaky electrolytic coupling capacitors, considerably increased the
incidence of
noisy volume controls.

Some can be cleaned easily and give long service before more attention is
required, whereas, if the track is badly worn, relief, if any, is only
temporary, no matter what you use.

In such cases, the only remedy is replacement.

These can typically be silenced just by connceting the
unconnected pot end to the wiper ...


There shouldn't be an unconnected end! The pot will typically be connected
between signal and ground with the output being between the wiper and ground.

Carbon pots carrying DC are much more prone to be noisy.

The change from valves to transistors, with their lower impedance
circuitry and
'leaky' electrolytic coupling capacitors, considerably increased the
incidence
of noisy volume controls.

Some can be cleaned easily and give long service before more attention is
required, whereas, if the track is badly worn, relief, if any, is only
temporary, no matter what you use.

In such cases, the only remedy is replacement.

*... or if that cant be done fitting a fixed R to the wiper and
ground or one
of the other terminals.


That will modify the 'law' of the pot and change the wiper position for most
settings. If the track is worn in the area that is most usually used (not
surprising!) moving the operating point to a relatively unused section can
work.

Fine as a diy work around but not worthwhile if a replacement is to hand as
that will give a better guarantee of a long term solution.



I wasnt quite clear was I. Sometimes the pot is wired such that if the
wiper goes oc, the output, which connects to the wiper, is o/c. Adding
a fixed R across the pot's output prevents this, ie from wiper to
ground end. It can be high enough value to have only a trivial effect
on the 'law' of the pot, which is a fairly trivial matter anyhow.

I wouldn't have thought that made the slightest bit of difference. If
the wiper's o/c, a resistor between the wiper and the ground end of the
pot still won't provide any output.

However, if the earthy end of the track has become disconnected from the
earthy connection pin, but is otherwise intact, the top of the pot and
the wiper is still a variable resistor. The volume will probably be
maximum, and more-or-less uncontrollable. Adding a resistor between the
slider and the earthy end will give you of degree of control.

The same is true if the top end of the track becomes detached from the
connection, except that the volume will be zero. Adding a resistor will
restore some output (albeit less than maximum), and a degree of control.
--
Ian
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On Mar 19, 4:20*pm, Ian Jackson
wrote:
In message
,
Tabby writes

On Mar 18, 4:59 pm, Terry Casey wrote:
In message

on Fri, 18 Mar 2011 08:52:07 -0700 (PDT)
Tabby wrote:


I have occasionally seen a volume pot carrying dc, but not wired up
correctly, ie arranged so that any slight poor connection produces a
lot of noise.


What do you mean by 'not wired up correctly'?


Carbon pots carrying DC are much more prone to be noisy.


The change from valves to transistors, with their lower impedance
circuitry and
leaky electrolytic coupling capacitors, considerably increased the
incidence of
noisy volume controls.


Some can be cleaned easily and give long service before more attention is
required, whereas, if the track is badly worn, relief, if any, is only
temporary, no matter what you use.


In such cases, the only remedy is replacement.


These can typically be silenced just by connceting the
unconnected pot end to the wiper ...


There shouldn't be an unconnected end! The pot will typically be connected
between signal and ground with the output being between the wiper and ground.


Carbon pots carrying DC are much more prone to be noisy.


The change from valves to transistors, with their lower impedance
circuitry and
'leaky' electrolytic coupling capacitors, considerably increased the
incidence
of noisy volume controls.


Some can be cleaned easily and give long service before more attention is
required, whereas, if the track is badly worn, relief, if any, is only
temporary, no matter what you use.


In such cases, the only remedy is replacement.


... or if that cant be done fitting a fixed R to the wiper and
ground or one
of the other terminals.


That will modify the 'law' of the pot and change the wiper position for most
settings. If the track is worn in the area that is most usually used (not
surprising!) moving the operating point to a relatively unused section can
work.


Fine as a diy work around but not worthwhile if a replacement is to hand as
that will give a better guarantee of a long term solution.


I wasnt quite clear was I. Sometimes the pot is wired such that if the
wiper goes oc, the output, which connects to the wiper, is o/c. Adding
a fixed R across the pot's output prevents this, ie from wiper to
ground end. It can be high enough value to have only a trivial effect
on the 'law' of the pot, which is a fairly trivial matter anyhow.


I wouldn't have thought that made the slightest bit of difference. If
the wiper's o/c, a resistor between the wiper and the ground end of the
pot still won't provide any output.

However, if the earthy end of the track has become disconnected from the
earthy connection pin, but is otherwise intact, the top of the pot and
the wiper is still a variable resistor. The volume will probably be
maximum, and more-or-less uncontrollable. Adding a resistor between the
slider and the earthy end will give you of degree of control.

The same is true if the top end of the track becomes detached from the
connection, except that the volume will be zero. Adding a resistor will
restore some output (albeit less than maximum), and a degree of control.


When the wiper connection goes o/c, you often get a dc offset showing
up on the output wire, creating major noise. Adding a resistor
prevents this, and can turn a very noisy pot into a silent well
behaved one, some of the time.


NT


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On Fri, 18 Mar 2011 12:07:34 +0000, The Other Mike
wrote:

For reference a major component of Servisol 'switch cleaner' is
petroleum distillate, a major component of WD40 is...petroleum
distillate. Of course petroleum distillate can cover a whole range of
products but you get the idea

Erme - anyone else abandoned the insulator element and the switch
cleaner element and gone straight over the the main ingredient,
petroleum distillate?

I'd run out of switch cleaner and rather than run out for switch
cleaner, I squirted some lighter fuel into some scratchy pots instead.
All the usual gunge dissolved out and the pots worked fine afterwards.

Nick
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In message , Skipweasel
writes
In article ,
says...
For reference a major component of Servisol 'switch cleaner' is
petroleum distillate, a major component of WD40 is...petroleum
distillate. Of course petroleum distillate can cover a whole range of
products but you get the idea

Erme - anyone else abandoned the insulator element and the switch
cleaner element and gone straight over the the main ingredient,
petroleum distillate?


The school is about to throw away its 1970s Russian stereo microscope
[1] and I perused the instructions. To degrease it on delivery you are
instructed to wash it with "High grade aviation gasoline". Can't see
that going down well with the insurers these days.

[1] I'll rescue it and repair it, but it'll have to go to another home
since I already have a much better one. All that's happened is the M2
screws that hold the binocular body onto the focussing slide have pulled
out. Drill and tap to M2.5 and fit new screws should fix it.

Hold it for me then

I'll be passing through shropshire next weekend


--
geoff
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In message
on Sat, 19 Mar 2011 07:08:00 -0700 (PDT)
Tabby wrote:

On Mar 18, 4:59Â*pm, Terry Casey wrote:
In message
on Fri, 18 Mar 2011 08:52:07 -0700 (PDT)
Â*Tabby wrote:

Â*... or if that cant be done fitting a fixed R to the wiper and ground or
one of the other terminals.


That will modify the 'law' of the pot and change the wiper position for most
settings. If the track is worn in the area that is most usually used (not
surprising!) moving the operating point to a relatively unused section can
work.

Fine as a diy work around but not worthwhile if a replacement is to hand as
that will give a better guarantee of a long term solution.



I wasnt quite clear was I. Sometimes the pot is wired such that if the
wiper goes oc, the output, which connects to the wiper, is o/c. Adding
a fixed R across the pot's output prevents this, ie from wiper to
ground end. It can be high enough value to have only a trivial effect
on the 'law' of the pot, which is a fairly trivial matter anyhow.


You are implying that you have understood my reference to changing the law of
the pot to be derogatory. This is not so - if you read it carefully, you will
see that I was simply pointing out that changing the law of the pot (within
reasonable limits, of course!) is the reason that your idea can successfully
move the normal operating point away from the worn area of the track.

However, if the wiper goes o/c *after* you've made your modification - and that
is the way I interpret your post - then the pot is useless: the only solution
is replacement.

--

Terry
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In message
on Sat, 19 Mar 2011 10:07:28 -0700 (PDT)
Tabby wrote:


When the wiper connection goes o/c, you often get a dc offset showing
up on the output wire, creating major noise. Adding a resistor
prevents this, and can turn a very noisy pot into a silent well
behaved one, some of the time.


"When the wiper connection goes o/c ..." the pot no longer works, noise or no
noise, so replace the bloody thing!

--

Terry


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In message , Skipweasel
writes
In article , says...
The school is about to throw away its 1970s Russian stereo microscope


Hold it for me then

I'll be passing through shropshire next weekend


If it isn't the BM-51-2 shown about half way down here...
http://www.microscopy-uk.org.uk/mag/...-TOE-Lomo.html
Then it's something very similar.

It's really nothing to write home about - but I hate to see things
thrown out when a few minutes work would fix them.

Better than nothing, which is what I have ATM

I should be in Shrewsbury next sunday, drop me some details


--
geoff
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On Mar 20, 11:37*am, Terry Casey wrote:
In message
on Sat, 19 Mar 2011 10:07:28 -0700 (PDT)
*Tabby wrote:



When the wiper connection goes o/c, you often get a dc offset showing
up on the output wire, creating major noise. Adding a resistor
prevents this, and can turn a very noisy pot into a silent well
behaved one, some of the time.


"When the wiper connection goes o/c ..." the pot no longer works, noise or no
noise, so replace the bloody thing!


Not at all, its common for pots to go momentarily o/c while rotating
them, and as long as its very brief its not normally noticed. If it
gets to the point where it is noticeable, then yes, its replacement
time.


NT
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On Fri, 18 Mar 2011 14:03:22 +0000, Jules Richardson wrote:
As an update, I tried some IPA, and that gave a huge improvement - in
fact, it was perfect for a few days. As of this morning I'm suddenly
getting signal drop-out on the left channel, but I suspect this isn't
related to switch/pot contacts.


Oh, and the other channel followed it some 30 mins or so later. Strange
that they didn't fail at the same time. It might be an age-related
component failure and it's just coincidence that both channels died
within a narrow space of time - or a single component failure has had
some kind of knock-on effect that's killed something in both channels
(and it took one side longer to go bad than the other).

I might get a chance later today to do some more in-depth digging.
Ignoring the tuner stages, I don't think this thing is particularly
complex, so it shouldn't take long to trace a schematic out.

cheers

Jules
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