My TV remote control has been a bit hit and miss. Sometimes it
works and sometimes it doesn't. I took it apart and cleaned it as
follows:

ONE
I carefully wiped some gunky residue (food? drink?) from inside
using tap water on a paper cloth to dissolve it. That included:

(a) the rear of the one-piece rubber keypad
(b) the part of the circuit board containing the key contacts

Maybe I should have used distilled water but I made sure I wiped
the water off until it was almost completely dry.

TWO
I then used isopropyl to remove any oils or grease residues on (a)
and (b) above.

------

I have read he
http://www.tvantenna.com/support/tut...oterepair.html
that the rear of the rubber contacts are coated with some special
conductive compound. I thought it was conductive rubber else I
expected some little pieces of metal foil behind each key. Oh
well!

Is water or alcohol likely to remove the coating that page refers
to?

Is it completely crazy to very LIGHTLY sandpaper the contacts on
the board? I would using 1,000 grit or even the soft "flour"
paper usd to finish off varnishes on furniture. The contacts look
like some sort of carbon and might take two or three very GENTLE
strokes.

Zak writes:

My TV remote control has been a bit hit and miss. Sometimes it
works and sometimes it doesn't. I took it apart and cleaned it as
follows:

ONE
I carefully wiped some gunky residue (food? drink?) from inside
using tap water on a paper cloth to dissolve it. That included:

(a) the rear of the one-piece rubber keypad
(b) the part of the circuit board containing the key contacts

Maybe I should have used distilled water but I made sure I wiped
the water off until it was almost completely dry.

TWO
I then used isopropyl to remove any oils or grease residues on (a)
and (b) above.

------

I have read he
http://www.tvantenna.com/support/tut...oterepair.html
that the rear of the rubber contacts are coated with some special
conductive compound. I thought it was conductive rubber else I
expected some little pieces of metal foil behind each key. Oh
well!

Is water or alcohol likely to remove the coating that page refers
to?

Is it completely crazy to very LIGHTLY sandpaper the contacts on
the board? I would using 1,000 grit or even the soft "flour"
paper usd to finish off varnishes on furniture. The contacts look
like some sort of carbon and might take two or three very GENTLE
strokes.

I would have started with just the cleaning using water and isopropyl.
That should be enough in most cases.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

On Wed, 15 Feb 2006 14:04:15 GMT, Zak Gave us:

My TV remote control has been a bit hit and miss. Sometimes it
works and sometimes it doesn't. I took it apart and cleaned it as
follows:

ONE
I carefully wiped some gunky residue (food? drink?) from inside
using tap water on a paper cloth to dissolve it. That included:

(a) the rear of the one-piece rubber keypad
(b) the part of the circuit board containing the key contacts

Battery contacts? New batteries?

Maybe I should have used distilled water but I made sure I wiped
the water off until it was almost completely dry.

One can use a 125 degree F oven to bake it for a half hour to ensure
complete dryness. That is below the temp for any plastic parts and
matches the "bake out" temp used in many industrial environments.
Approximately 60 to 65 C.

TWO
I then used isopropyl to remove any oils or grease residues on (a)
and (b) above.

Make sure it is 99% IPA as the weaker IPA is cut with water!

I have read he
http://www.tvantenna.com/support/tut...oterepair.html
that the rear of the rubber contacts are coated with some special
conductive compound.

They are usually thick pads of what is referred to as "carburized
rubber".

I thought it was conductive rubber else I
expected some little pieces of metal foil behind each key.

I don't know of any current models that are not regular carburized
rubber LV resistive "switches".


Oh
well!

Bake it out (no batteries of course).

Is water or alcohol likely to remove the coating that page refers
to?

There is sometimes a coating on the PCB pads. One must be careful
not to abrade those. If they are bare metal, one CAN abrade them
lightly with a pencil eraser (lightly).

Is it completely crazy to very LIGHTLY sandpaper the contacts on
the board?

NO SANDPAPER. For one thing, it has a huge triboelectric effect, and
will introduce electrostatic charges into the PCB assembly, perhaps
causing an ESD event, which could damage the circuit.

I would using 1,000 grit or even the soft "flour"
paper usd to finish off varnishes on furniture.

Pencil erasers are abrasive enough, and remove very little surface
molecules. More like a an oxide rubbing, to remove any oxides on the
(likely brass or gold) plated contacts.


The contacts look
like some sort of carbon and might take two or three very GENTLE
strokes.

No. If the PCB has carbon painted (or screened) spot, you do NOT want
to do any of the above. They will remain conductive just fine. The
bake out is all you really likely need, and good battery contacts, and
good batteries, and make sure the receiving end is unobstructed (dust
on the window or an item in front of it).

In article , Roy L. Fuchs wrote:
On Wed, 15 Feb 2006 14:04:15 GMT, Zak Gave us:

My TV remote control has been a bit hit and miss. Sometimes it
works and sometimes it doesn't. I took it apart and cleaned it as
follows:

ONE
I carefully wiped some gunky residue (food? drink?) from inside
using tap water on a paper cloth to dissolve it. That included:

(a) the rear of the one-piece rubber keypad
(b) the part of the circuit board containing the key contacts

Battery contacts? New batteries?

Maybe I should have used distilled water but I made sure I wiped
the water off until it was almost completely dry.

One can use a 125 degree F oven to bake it for a half hour to ensure
complete dryness. That is below the temp for any plastic parts and
matches the "bake out" temp used in many industrial environments.
Approximately 60 to 65 C.

TWO
I then used isopropyl to remove any oils or grease residues on (a)
and (b) above.

Make sure it is 99% IPA as the weaker IPA is cut with water!

I'm not sure that high octane alcohol is always needed. My point, as alcohol
dries, the water percentage goes up rapidly, attaining 0% alcohol
when it dries, and the remaining water accumulated from the moisturing
grabbing alcohol, stays around until it evaporates. Hot air
drying is almost always needed during the process.

greg

I have read he
http://www.tvantenna.com/support/tut...oterepair.html
that the rear of the rubber contacts are coated with some special
conductive compound.

They are usually thick pads of what is referred to as "carburized
rubber".

I thought it was conductive rubber else I
expected some little pieces of metal foil behind each key.

I don't know of any current models that are not regular carburized
rubber LV resistive "switches".


Oh
well!

Bake it out (no batteries of course).

Is water or alcohol likely to remove the coating that page refers
to?

There is sometimes a coating on the PCB pads. One must be careful
not to abrade those. If they are bare metal, one CAN abrade them
lightly with a pencil eraser (lightly).

Is it completely crazy to very LIGHTLY sandpaper the contacts on
the board?

NO SANDPAPER. For one thing, it has a huge triboelectric effect, and
will introduce electrostatic charges into the PCB assembly, perhaps
causing an ESD event, which could damage the circuit.

I would using 1,000 grit or even the soft "flour"
paper usd to finish off varnishes on furniture.

Pencil erasers are abrasive enough, and remove very little surface
molecules. More like a an oxide rubbing, to remove any oxides on the
(likely brass or gold) plated contacts.


The contacts look
like some sort of carbon and might take two or three very GENTLE
strokes.

No. If the PCB has carbon painted (or screened) spot, you do NOT want
to do any of the above. They will remain conductive just fine. The
bake out is all you really likely need, and good battery contacts, and
good batteries, and make sure the receiving end is unobstructed (dust
on the window or an item in front of it).

On Wed, 15 Feb 2006 15:00:43 GMT, (GregS) Gave us:

I'm not sure that high octane alcohol is always needed. My point, as alcohol
dries, the water percentage goes up rapidly, attaining 0% alcohol
when it dries, and the remaining water accumulated from the moisturing
grabbing alcohol, stays around until it evaporates. Hot air
drying is almost always needed during the process.

greg

That depends on the temperature of the board AND the alcohol.

If both are warm, the alcohol will NOT leave any "dew" behind. It
will dry 100% , quickly and free of water.

IPA heats up in a microwave just fine. A small cup for 15 seconds
up to as much as a minute or so for about half a cup will get it very
near its boiling point. It also works much better as a solvent /
cleaner when it is hot like that, and evaporates nearly instantly.
I have set up many a production floor with vapor phase degreaser
machines using various solvent media.

Hot air drying is NOT "almost always needed" if one starts with
things in the right conditions to begin with.

If the PCB and assembly is hot, it will be pushing water OUT of it,
not absorbing it. Just make sure that it returns to room temp in a
dry box (ie the oven that got it hot). Not required though unless the
climate is VERY humid.

The last step should always be the half hour 120F bake out if one
REALLY wants all the water out of the hygroscopic PCB..

"Zak" wrote in message
...
My TV remote control has been a bit hit and miss. Sometimes it
works and sometimes it doesn't. I took it apart and cleaned it as
follows:

ONE
I carefully wiped some gunky residue (food? drink?) from inside
using tap water on a paper cloth to dissolve it. That included:

Snipped a bunch

Uhhh. . . buy a new one? They're about $5 now.

--
Regards,

Paul

On Wed, 15 Feb 2006 15:00:43 GMT, (GregS) Gave us:

I'm not sure that high octane alcohol is always needed.


Hahahaha... that's funny. The alcohol with the higher water content
(ie 70% or 50%) would have the higher octane number.

Methinks you chose the wrong adjective today! :-]

Higher *purity* is the 99%. But lower octane number (if it even has
one).

Octane is a measure of a volatile liquid or mist or gas and air mix
to resist detonation by heat or pressure before deliberately being
ignited by the spark. So, 99 octane gas actually burns with a little
LESS energy than 89 octane.

What the higher octane allowed a racer or engine maker to do is raise
compression ratios and combustion chamber temperature without the
worry of "pre-ignition" or detonation before the desired point in the
stroke.

Not saying that you didn't know that, just iterating.

In article , Roy L. Fuchs wrote:
On Wed, 15 Feb 2006 15:00:43 GMT, (GregS) Gave us:

I'm not sure that high octane alcohol is always needed. My point, as alcohol
dries, the water percentage goes up rapidly, attaining 0% alcohol
when it dries, and the remaining water accumulated from the moisturing
grabbing alcohol, stays around until it evaporates. Hot air
drying is almost always needed during the process.

greg

That depends on the temperature of the board AND the alcohol.

If both are warm, the alcohol will NOT leave any "dew" behind. It
will dry 100% , quickly and free of water.

IPA heats up in a microwave just fine. A small cup for 15 seconds
up to as much as a minute or so for about half a cup will get it very
near its boiling point. It also works much better as a solvent /
cleaner when it is hot like that, and evaporates nearly instantly.
I have set up many a production floor with vapor phase degreaser
machines using various solvent media.

Hot air drying is NOT "almost always needed" if one starts with
things in the right conditions to begin with.

If the PCB and assembly is hot, it will be pushing water OUT of it,
not absorbing it. Just make sure that it returns to room temp in a
dry box (ie the oven that got it hot). Not required though unless the
climate is VERY humid.

The last step should always be the half hour 120F bake out if one
REALLY wants all the water out of the hygroscopic PCB..

I have never thought od heating alcohol for obvious reasons, but
this may come in handy for stubborn cases. I had some boards
that the caps would absorb moisture or other stuff, and would
take days, months to dry without baking. I usually just
use a hot air pencil or gun to heat up boards.

greg

On Wed, 15 Feb 2006 15:34:11 GMT, (GregS) Gave us:

In article , Roy L. Fuchs wrote:
On Wed, 15 Feb 2006 15:00:43 GMT, (GregS) Gave us:

I'm not sure that high octane alcohol is always needed. My point, as alcohol
dries, the water percentage goes up rapidly, attaining 0% alcohol
when it dries, and the remaining water accumulated from the moisturing
grabbing alcohol, stays around until it evaporates. Hot air
drying is almost always needed during the process.

greg

That depends on the temperature of the board AND the alcohol.

If both are warm, the alcohol will NOT leave any "dew" behind. It
will dry 100% , quickly and free of water.

IPA heats up in a microwave just fine. A small cup for 15 seconds
up to as much as a minute or so for about half a cup will get it very
near its boiling point. It also works much better as a solvent /
cleaner when it is hot like that, and evaporates nearly instantly.
I have set up many a production floor with vapor phase degreaser
machines using various solvent media.

Hot air drying is NOT "almost always needed" if one starts with
things in the right conditions to begin with.

If the PCB and assembly is hot, it will be pushing water OUT of it,
not absorbing it. Just make sure that it returns to room temp in a
dry box (ie the oven that got it hot). Not required though unless the
climate is VERY humid.

The last step should always be the half hour 120F bake out if one
REALLY wants all the water out of the hygroscopic PCB..

I have never thought od heating alcohol for obvious reasons, but
this may come in handy for stubborn cases. I had some boards
that the caps would absorb moisture or other stuff, and would
take days, months to dry without baking. I usually just
use a hot air pencil or gun to heat up boards.


Yet that practice is very dangerous. Even a toaster oven is safer
as it would heat the whole board uniformly (relatively). The pencil
is way too high a heat, and even feathered across the area desired is
a shock to the media, every time. Blow driers and heat shrink guns
can be used if they are kept far far away so that the heat has a
chance to cool a few hundred degrees as it passes thru the cool air on
its way to the target. Still the oven (toaster or otherwise) is
better. 120 F... 60 - 65 C.

In article , Roy L. Fuchs wrote:
On Wed, 15 Feb 2006 15:34:11 GMT, (GregS) Gave us:

In article , Roy L. Fuchs
wrote:
On Wed, 15 Feb 2006 15:00:43 GMT, (GregS) Gave us:

I'm not sure that high octane alcohol is always needed. My point, as alcohol
dries, the water percentage goes up rapidly, attaining 0% alcohol
when it dries, and the remaining water accumulated from the moisturing
grabbing alcohol, stays around until it evaporates. Hot air
drying is almost always needed during the process.

greg

That depends on the temperature of the board AND the alcohol.

If both are warm, the alcohol will NOT leave any "dew" behind. It
will dry 100% , quickly and free of water.

IPA heats up in a microwave just fine. A small cup for 15 seconds
up to as much as a minute or so for about half a cup will get it very
near its boiling point. It also works much better as a solvent /
cleaner when it is hot like that, and evaporates nearly instantly.
I have set up many a production floor with vapor phase degreaser
machines using various solvent media.

Hot air drying is NOT "almost always needed" if one starts with
things in the right conditions to begin with.

If the PCB and assembly is hot, it will be pushing water OUT of it,
not absorbing it. Just make sure that it returns to room temp in a
dry box (ie the oven that got it hot). Not required though unless the
climate is VERY humid.

The last step should always be the half hour 120F bake out if one
REALLY wants all the water out of the hygroscopic PCB..

I have never thought od heating alcohol for obvious reasons, but
this may come in handy for stubborn cases. I had some boards
that the caps would absorb moisture or other stuff, and would
take days, months to dry without baking. I usually just
use a hot air pencil or gun to heat up boards.


Yet that practice is very dangerous. Even a toaster oven is safer
as it would heat the whole board uniformly (relatively). The pencil
is way too high a heat, and even feathered across the area desired is
a shock to the media, every time. Blow driers and heat shrink guns
can be used if they are kept far far away so that the heat has a
chance to cool a few hundred degrees as it passes thru the cool air on
its way to the target. Still the oven (toaster or otherwise) is
better. 120 F... 60 - 65 C.

I have one of those hot air pencils with complete control of temp and flow.

I sometimes use a 100 watt lamp over the board.

greg

Zak wrote:
My TV remote control has been a bit hit and miss. Sometimes it
works and sometimes it doesn't. I took it apart and cleaned it as
follows:

ONE
I carefully wiped some gunky residue (food? drink?) from inside
using tap water on a paper cloth to dissolve it. That included:

(a) the rear of the one-piece rubber keypad
(b) the part of the circuit board containing the key contacts

Maybe I should have used distilled water but I made sure I wiped
the water off until it was almost completely dry.

TWO
I then used isopropyl to remove any oils or grease residues on (a)
and (b) above.

------

I have read he
http://www.tvantenna.com/support/tut...oterepair.html
that the rear of the rubber contacts are coated with some special
conductive compound. I thought it was conductive rubber else I
expected some little pieces of metal foil behind each key. Oh
well!

Is water or alcohol likely to remove the coating that page refers
to?

I'd avoid the use of solvents like IPA since you'll think the dirty mark
is
dirt when it may well be the carbon coating coming off!

Is it completely crazy to very LIGHTLY sandpaper the contacts on
the board? I would using 1,000 grit or even the soft "flour"
paper usd to finish off varnishes on furniture. The contacts look
like some sort of carbon and might take two or three very GENTLE
strokes.

No - don't do it! There is very little coating present and you don't want
to lose any of it.

Once it has been cleaned with water and dabbed dry, put in the
airing cupboard or other warm - NOT hot - place to completely dry.

Then reassembe and test.

HTH
--
Graham W http://www.gcw.org.uk/ PGM-FI page updated, Graphics Tutorial
WIMBORNE http://www.wessex-astro-society.freeserve.co.uk/ Wessex
Dorset UK Astro Society's Web pages, Info, Meeting Dates, Sites & Maps
Change 'news' to 'sewn' in my Reply address to avoid my spam filter.