[Michael Dobony]

I have an all-in-one AC/furnace sitting outside. The circuit board was
replaced a very short time ago, about two months ago. It is already showing
signs of degradation (rust on a diode lead). Is there any spray coating I
can put on this to prevent further degradation, assuming it is still in
operating condition?

This is a link to the type of unit I have
http://www.americanstandardair.com/P...ckaged+Systems

Mike D.

[Home Guy]

Michael Dobony wrote:

I have an all-in-one AC/furnace sitting outside. The circuit board
was replaced a very short time ago, about two months ago. It is
already showing signs of degradation (rust on a diode lead).

Is there any spray coating I can put on this to prevent further
degradation, assuming it is still in operating condition?

What will probably do the job is something called "conformal coating".

Here's one example:

http://www.mgchemicals.com/products/422a.html

==============
Silicone Conformal Coating

Ideal for high temperature environments. Silicone Conformal Coating
(422A) is a flexible finish product that provides a protective coating
for printed circuit boards against moisture, corrosion, and thermal
shock. It protects and insulates electrical and electronic components
and assemblies, including generators, motors, transformers, relays, and
solenoid coils. For spraying, liquid can be thinned using M.G. Thinner
Cleaner. Thin up to one half part thinner to one part coating. Also
available in a micro tip pen format.
==============

I'd remove the board, clean it by pouring some drug-store alcohol over
it while scrubbing it with a soft brush, let it dry completely and then
apply the coating.

If the board is relatively clean, then maybe just turn off power the the
AC unit and spray the board with the coating without taking it out.

[Stormin Mormon]

WD-40 comes to mind. But, is it a water displacer, or a
lubricant? The myseries of the universe.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Michael Dobony" wrote in
message . ..
I have an all-in-one AC/furnace sitting outside. The circuit
board was
replaced a very short time ago, about two months ago. It is
already showing
signs of degradation (rust on a diode lead). Is there any
spray coating I
can put on this to prevent further degradation, assuming it
is still in
operating condition?

This is a link to the type of unit I have
http://www.americanstandardair.com/P...ckaged+Systems

Mike D.

[Ron]

On Nov 16, 6:16*pm, Home Guy wrote:
Michael Dobony wrote:
I have an all-in-one AC/furnace sitting outside. The circuit board
was replaced a very short time ago, about two months ago. It is
already showing signs of degradation (rust on a diode lead).
Is there any spray coating I can put on this to prevent further
degradation, assuming it is still in operating condition?

What will probably do the job is something called "conformal coating".

Here's one example:

http://www.mgchemicals.com/products/422a.html

==============
Silicone Conformal Coating

Ideal for high temperature environments. Silicone Conformal Coating
(422A) is a flexible finish product that provides a protective coating
for printed circuit boards against moisture, corrosion, and thermal
shock. It protects and insulates electrical and electronic components
and assemblies, including generators, motors, transformers, relays, and
solenoid coils. For spraying, liquid can be thinned using M.G. Thinner
Cleaner. Thin up to one half part thinner to one part coating. Also
available in a micro tip pen format.
==============

I'd remove the board, clean it by pouring some drug-store alcohol over
it while scrubbing it with a soft brush, let it dry completely and then
apply the coating.

If the board is relatively clean, then maybe just turn off power the the
AC unit and spray the board with the coating without taking it out.

http://tangentsoft.net/elec/movies/tt05.html

[mike]

Home Guy wrote:
Michael Dobony wrote:

I have an all-in-one AC/furnace sitting outside. The circuit board
was replaced a very short time ago, about two months ago. It is
already showing signs of degradation (rust on a diode lead).

Is there any spray coating I can put on this to prevent further
degradation, assuming it is still in operating condition?

What will probably do the job is something called "conformal coating".

Here's one example:

http://www.mgchemicals.com/products/422a.html

==============
Silicone Conformal Coating

Ideal for high temperature environments. Silicone Conformal Coating
(422A) is a flexible finish product that provides a protective coating
for printed circuit boards against moisture, corrosion, and thermal
shock. It protects and insulates electrical and electronic components
and assemblies, including generators, motors, transformers, relays, and
solenoid coils. For spraying, liquid can be thinned using M.G. Thinner
Cleaner. Thin up to one half part thinner to one part coating. Also
available in a micro tip pen format.
==============

I'd remove the board, clean it by pouring some drug-store alcohol over
it while scrubbing it with a soft brush, let it dry completely and then
apply the coating.

If the board is relatively clean, then maybe just turn off power the the
AC unit and spray the board with the coating without taking it out.

In any repair situation, it's important to fix the thing that's broke.
Any product designed to sit outside MUST be capable of withstanding
the environment. Unless you're near an ocean, your environment is likely
way less corrosive than the design/test environment.

I'd call the vendor or the installer and see what they have to say about it.
Then I'd look at how the board is configured and make sure the enclosure
isn't missing a gasket, or bent, or has an open screw hole in it.
Seal it up tight. Make sure it's dry inside when you're done.

Conformal coating seems attractive on the surface.
Of course, it's gonna void the warranty and make the board very difficult
to repair.
It has thermal resistance, so any component depending on convection
cooling will be compromised.

If you decide to clean it, be aware that some components may not like
being drenched in alcohol and water.

Spraying the board in place may not be effective. You need to seal
the back and the edges of the board.

If you decide to coat it, dry it as discussed above, then dry it again.
Doesn't do a lot of good to keep out the water when the water's already
under the coating.

Still think I'd seal the enclosure first.

[gregz]

"Stormin Mormon" wrote:
WD-40 comes to mind. But, is it a water displacer, or a
lubricant? The myseries of the universe.


Oil floats on water, not the other way around. It evaporates quickly, so
it's not a good lube.

That being said, sometimes after I wash electronics with water, Then spray
with wd40, and continue drying with heat.

Aside from usual conformal coatings, when clean and dry, might spray with
Krylon crystal clear varnish coating. Then bake.

Greg

[gregz]

gregz wrote:
"Stormin Mormon" wrote:
WD-40 comes to mind. But, is it a water displacer, or a
lubricant? The myseries of the universe.


Oil floats on water, not the other way around. It evaporates quickly, so
it's not a good lube.

That being said, sometimes after I wash electronics with water, Then spray
with wd40, and continue drying with heat.

Aside from usual conformal coatings, when clean and dry, might spray with
Krylon crystal clear varnish coating. Then bake.

Greg

It's more like automotive enamel. Don't use lacquer, a poor barrier against
moisture.

Greg

[Ron]

On Nov 16, 8:03*pm, gregz wrote:

That being said, sometimes after I wash electronics with water, Then spray
with wd40, and continue drying with heat.

What electronics do you wash with water?

[Stormin Mormon]

Enquiring minds want to know. Clothes washer, or dish
washer? Front or top loader? Circuit boards, green. Goes in
with colors?

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Ron" wrote in message
...
On Nov 16, 8:03 pm, gregz wrote:

That being said, sometimes after I wash electronics with
water, Then spray
with wd40, and continue drying with heat.

What electronics do you wash with water?

[Stormin Mormon]

I wonder if the Fed has a circuit board protection program?

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..

[Tony Miklos[_2_]]

On 11/16/2011 9:01 PM, Ron wrote:
On Nov 16, 8:03 pm, wrote:

That being said, sometimes after I wash electronics with water, Then spray
with wd40, and continue drying with heat.

What electronics do you wash with water?

I've washed hundreds of circuit boards with a water based solution and
rinsed with plain old hard well water. Usually but not always I use
compressed air to blow the water off the board. Just so it's dry before
being powered up it's fine. I even ran some through the dishwasher once
just to prove my point. I did use baking soda instead of dishwasher
detergent. All of them survived.

[mike]

Ron wrote:
On Nov 16, 8:03 pm, gregz wrote:

That being said, sometimes after I wash electronics with water, Then spray
with wd40, and continue drying with heat.

What electronics do you wash with water?

Much of the electronics in the world has been washed in water as
part of the assembly process.
There are components that can't stand it, so you gotta be careful.
I wash circuit boards in Simple Green cleaner, then alcohol then water
then do it again. Blow off the water with compressed air between washes,
then repeat again. Some gunk is soluble in simple green, some in alcohol,
you need both.
Scrub with a toothbrush at every stage.
Doesn't do much good to dissolve the stuff then let the solvent evaporate.
Blowing off is critical to the process. Get all the liquid out from
under parts. Space under a surface mount IC can be tiny.
Dry it then dry it again then dry it some more.
Works wonders on removing residue from leaky electrolytic capacitors.

Some people use the dishwasher. I don't because It's harder to mask
components that can't be washed.
General rules of thumb include:
1)don't get solvent into anything that changes properties under the
influence.
2)don't get solvent into electromechanical stuff.
3)don't get solvent into anything that it can't easily get out of.
It's really easy to let contaminated solvent seep into a switch, but
it's very
difficult to get it ALL out. Evaporation is not an option, cause
the process deposits more gunk and leaves it behind.

[[email protected]]

On Wed, 16 Nov 2011 16:45:47 -0600, Michael Dobony
wrote:

I have an all-in-one AC/furnace sitting outside. The circuit board was
replaced a very short time ago, about two months ago. It is already showing
signs of degradation (rust on a diode lead). Is there any spray coating I
can put on this to prevent further degradation, assuming it is still in
operating condition?

This is a link to the type of unit I have
http://www.americanstandardair.com/P...ckaged+Systems

Mike D.
Silicone conformal coatings are very COMMON in the electronics world,
and SHOULD be standard equipment on all circuit boards in things like
furnaces , washers, dries, etc. You can easily buy them from
electronics supply houses and apply them yourself (spray cans),
taking care to protect connectors etc.
The only problem is it makes board repair somewhat difficult - but the
majority of circuit boards on equipment today is pretty much
non-repairable anyway.

[[email protected]]

On Wed, 16 Nov 2011 18:51:35 -0500, "Stormin Mormon"
wrote:

WD-40 comes to mind. But, is it a water displacer, or a
lubricant? The myseries of the universe.
And not worth squat as a circuit board protector. Might want to try
LPS2 - but at best it is also only a temporaty protection - and it
holds dirt etc.

Like I said before - silicone conformal coating - applied to a CLEAN
board when new.

[Michael Dobony]

On Wed, 16 Nov 2011 18:16:59 -0500, Home Guy wrote:

Michael Dobony wrote:

I have an all-in-one AC/furnace sitting outside. The circuit board
was replaced a very short time ago, about two months ago. It is
already showing signs of degradation (rust on a diode lead).

Is there any spray coating I can put on this to prevent further
degradation, assuming it is still in operating condition?

What will probably do the job is something called "conformal coating".

Here's one example:

http://www.mgchemicals.com/products/422a.html

==============
Silicone Conformal Coating

Ideal for high temperature environments. Silicone Conformal Coating
(422A) is a flexible finish product that provides a protective coating
for printed circuit boards against moisture, corrosion, and thermal
shock. It protects and insulates electrical and electronic components
and assemblies, including generators, motors, transformers, relays, and
solenoid coils. For spraying, liquid can be thinned using M.G. Thinner
Cleaner. Thin up to one half part thinner to one part coating. Also
available in a micro tip pen format.
==============

I'd remove the board, clean it by pouring some drug-store alcohol over
it while scrubbing it with a soft brush, let it dry completely and then
apply the coating.

If the board is relatively clean, then maybe just turn off power the the
AC unit and spray the board with the coating without taking it out.

I looked at the info on these coatings. They need to be baked on after
application.

[Paul Drahn]

On 11/16/2011 6:42 PM, mike wrote:
Ron wrote:
On Nov 16, 8:03 pm, gregz wrote:

That being said, sometimes after I wash electronics with water, Then
spray
with wd40, and continue drying with heat.

What electronics do you wash with water?

Much of the electronics in the world has been washed in water as
part of the assembly process.
There are components that can't stand it, so you gotta be careful.
I wash circuit boards in Simple Green cleaner, then alcohol then water
then do it again. Blow off the water with compressed air between washes,
then repeat again. Some gunk is soluble in simple green, some in alcohol,
you need both.
Scrub with a toothbrush at every stage.
Doesn't do much good to dissolve the stuff then let the solvent evaporate.
Blowing off is critical to the process. Get all the liquid out from
under parts. Space under a surface mount IC can be tiny.
Dry it then dry it again then dry it some more.
Works wonders on removing residue from leaky electrolytic capacitors.

Some people use the dishwasher. I don't because It's harder to mask
components that can't be washed.
General rules of thumb include:
1)don't get solvent into anything that changes properties under the
influence.
2)don't get solvent into electromechanical stuff.
3)don't get solvent into anything that it can't easily get out of.
It's really easy to let contaminated solvent seep into a switch, but
it's very
difficult to get it ALL out. Evaporation is not an option, cause
the process deposits more gunk and leaves it behind.
That's what we do. Wash all boards with hot deionized water in a
commercial board washer. I think the temp is around 140 degrees F. Looks
like a very expensive dish washer. All water is recirculated through
tanks to clean and deionize the water. We have a regular Sears dish
washer for backup and that water goes down the drain.

After the washer tries to dry the boards, the excess water is blown off
using deionized compressed air, being extra careful to clear all water
from under components. After that, they are air dried for a while.

All components that can't be washed are hand added after washing. Flux
from that operation is cleaned with IPA, isopropal alcohol. Sometimes a
manufacturer fails to state on their component spec sheet that the unit
can't be washed and then there is trouble, but most do tell you.

Paul

[Michael Dobony]

On Wed, 16 Nov 2011 16:04:27 -0800, mike wrote:

Home Guy wrote:
Michael Dobony wrote:

I have an all-in-one AC/furnace sitting outside. The circuit board
was replaced a very short time ago, about two months ago. It is
already showing signs of degradation (rust on a diode lead).

Is there any spray coating I can put on this to prevent further
degradation, assuming it is still in operating condition?

What will probably do the job is something called "conformal coating".

Here's one example:

http://www.mgchemicals.com/products/422a.html

==============
Silicone Conformal Coating

Ideal for high temperature environments. Silicone Conformal Coating
(422A) is a flexible finish product that provides a protective coating
for printed circuit boards against moisture, corrosion, and thermal
shock. It protects and insulates electrical and electronic components
and assemblies, including generators, motors, transformers, relays, and
solenoid coils. For spraying, liquid can be thinned using M.G. Thinner
Cleaner. Thin up to one half part thinner to one part coating. Also
available in a micro tip pen format.
==============

I'd remove the board, clean it by pouring some drug-store alcohol over
it while scrubbing it with a soft brush, let it dry completely and then
apply the coating.

If the board is relatively clean, then maybe just turn off power the the
AC unit and spray the board with the coating without taking it out.

In any repair situation, it's important to fix the thing that's broke.
Any product designed to sit outside MUST be capable of withstanding
the environment. Unless you're near an ocean, your environment is likely
way less corrosive than the design/test environment.

I'd call the vendor or the installer and see what they have to say about it.
Then I'd look at how the board is configured and make sure the enclosure
isn't missing a gasket, or bent, or has an open screw hole in it.
Seal it up tight. Make sure it's dry inside when you're done.

LOL!!!!! The panel covering it is held on with two screws and the cover has
no gasket and is ventilated to the outside. It experiences the same
atmospheric conditions as exist outside, like an open porch with open
horizontal blind style windows. To seal it up also would seal up the air
from the furnace burner.


Conformal coating seems attractive on the surface.
Of course, it's gonna void the warranty and make the board very difficult
to repair.
It has thermal resistance, so any component depending on convection
cooling will be compromised.

If you decide to clean it, be aware that some components may not like
being drenched in alcohol and water.

Spraying the board in place may not be effective. You need to seal
the back and the edges of the board.

If you decide to coat it, dry it as discussed above, then dry it again.
Doesn't do a lot of good to keep out the water when the water's already
under the coating.

Still think I'd seal the enclosure first.

Total reengineering and moving the board to a totally new location.

[Jim Yanik]

gregz wrote in

g:

"Stormin Mormon" wrote:
WD-40 comes to mind. But, is it a water displacer, or a
lubricant? The myseries of the universe.

it's mostly kerosene,dewaxed.(around 70%) Check the MSDS....carefully.


Oil floats on water, not the other way around. It evaporates quickly,
so it's not a good lube.

That being said, sometimes after I wash electronics with water, Then
spray with wd40, and continue drying with heat.

Aside from usual conformal coatings, when clean and dry, might spray
with Krylon crystal clear varnish coating. Then bake.

Greg


spray your circuit boards or electronics with WD-40 and heat,and you'll end
up with a gummy PCB/unit that attracts dirt. you want to REMOVE oils,not
add them.
If you want to remove water,use 90% isopropyl alcohol,then air dry.

At Tektronix,I washed PCBs,blew them off with air,and then dried them in an
oven at 140degF. I used to spray-wash entire
instruments(oscilloscopes,signal generators,etc),just to get all the
dirt,oil and grease off them. Even tobacco film.(yecch)
then 3 days minimum in the drying oven.
I even used a home auto dishwasher and Calgonite to clean/degrease high-Z
voltmeter PCBs.

--
Jim Yanik
jyanik
at
localnet
dot com

[JIMMIE]

On Nov 16, 6:16*pm, Home Guy wrote:
Michael Dobony wrote:
I have an all-in-one AC/furnace sitting outside. The circuit board
was replaced a very short time ago, about two months ago. It is
already showing signs of degradation (rust on a diode lead).
Is there any spray coating I can put on this to prevent further
degradation, assuming it is still in operating condition?

What will probably do the job is something called "conformal coating".

Here's one example:

http://www.mgchemicals.com/products/422a.html

==============
Silicone Conformal Coating

Ideal for high temperature environments. Silicone Conformal Coating
(422A) is a flexible finish product that provides a protective coating
for printed circuit boards against moisture, corrosion, and thermal
shock. It protects and insulates electrical and electronic components
and assemblies, including generators, motors, transformers, relays, and
solenoid coils. For spraying, liquid can be thinned using M.G. Thinner
Cleaner. Thin up to one half part thinner to one part coating. Also
available in a micro tip pen format.
==============

I'd remove the board, clean it by pouring some drug-store alcohol over
it while scrubbing it with a soft brush, let it dry completely and then
apply the coating.

If the board is relatively clean, then maybe just turn off power the the
AC unit and spray the board with the coating without taking it out.

Krylon makes an electical coating this should not be confused with
clear Krylon. Board should be cleaned before it is applied or you may
trap in corrosive material. already on the board.. Plug in connectors
should be masked off to keep the Krylon out of the connectors. Use a
little electrical grease on the connectors. The grease can be obtained
at local automotive parts store. They sell it in little packets for
greaseing up turn signal and break light bulbs.

Jimmie

[mike]

Michael Dobony wrote:
On Wed, 16 Nov 2011 16:04:27 -0800, mike wrote:

Home Guy wrote:
Michael Dobony wrote:

I have an all-in-one AC/furnace sitting outside. The circuit board
was replaced a very short time ago, about two months ago. It is
already showing signs of degradation (rust on a diode lead).
Is there any spray coating I can put on this to prevent further
degradation, assuming it is still in operating condition?
What will probably do the job is something called "conformal coating".

Here's one example:

http://www.mgchemicals.com/products/422a.html

==============
Silicone Conformal Coating

Ideal for high temperature environments. Silicone Conformal Coating
(422A) is a flexible finish product that provides a protective coating
for printed circuit boards against moisture, corrosion, and thermal
shock. It protects and insulates electrical and electronic components
and assemblies, including generators, motors, transformers, relays, and
solenoid coils. For spraying, liquid can be thinned using M.G. Thinner
Cleaner. Thin up to one half part thinner to one part coating. Also
available in a micro tip pen format.
==============

I'd remove the board, clean it by pouring some drug-store alcohol over
it while scrubbing it with a soft brush, let it dry completely and then
apply the coating.

If the board is relatively clean, then maybe just turn off power the the
AC unit and spray the board with the coating without taking it out.
In any repair situation, it's important to fix the thing that's broke.
Any product designed to sit outside MUST be capable of withstanding
the environment. Unless you're near an ocean, your environment is likely
way less corrosive than the design/test environment.

I'd call the vendor or the installer and see what they have to say about it.
Then I'd look at how the board is configured and make sure the enclosure
isn't missing a gasket, or bent, or has an open screw hole in it.
Seal it up tight. Make sure it's dry inside when you're done.

LOL!!!!! The panel covering it is held on with two screws and the cover has
no gasket and is ventilated to the outside. It experiences the same
atmospheric conditions as exist outside, like an open porch with open
horizontal blind style windows. To seal it up also would seal up the air
from the furnace burner.

Sounds like you've got a very bad design, or have installed an "inside"
box outside where it doesn't belong.
What does the vendor/installer say about it?

Conformal coating seems attractive on the surface.
Of course, it's gonna void the warranty and make the board very difficult
to repair.
It has thermal resistance, so any component depending on convection
cooling will be compromised.

If you decide to clean it, be aware that some components may not like
being drenched in alcohol and water.

Spraying the board in place may not be effective. You need to seal
the back and the edges of the board.

If you decide to coat it, dry it as discussed above, then dry it again.
Doesn't do a lot of good to keep out the water when the water's already
under the coating.

Still think I'd seal the enclosure first.

Total reengineering and moving the board to a totally new location.

[JIMMIE]

On Nov 16, 9:22*pm, "Stormin Mormon"
wrote:
Enquiring minds want to know. Clothes washer, or dish
washer? Front or top loader? Circuit boards, green. Goes in
with colors?

--
Christopher A. Young
Learn more about Jesus
*www.lds.org
.

"Ron" wrote in message

...
On Nov 16, 8:03 pm, gregz wrote:

That being said, sometimes after I wash electronics with
water, Then spray
with wd40, and continue drying with heat.

What electronics do you wash with water?

Most circuit boards that dont have switches or variable resistors or
variable caps can be cleaned in a dishwasher just fine.I have cleaned
many boards in an ultrasonic cleaner using water.

Jimmie

Jimmie

[[email protected]]

On Wed, 16 Nov 2011 21:29:39 -0600, Michael Dobony
wrote:

On Wed, 16 Nov 2011 18:16:59 -0500, Home Guy wrote:

Michael Dobony wrote:

I have an all-in-one AC/furnace sitting outside. The circuit board
was replaced a very short time ago, about two months ago. It is
already showing signs of degradation (rust on a diode lead).

Is there any spray coating I can put on this to prevent further
degradation, assuming it is still in operating condition?

What will probably do the job is something called "conformal coating".

Here's one example:

http://www.mgchemicals.com/products/422a.html

==============
Silicone Conformal Coating

Ideal for high temperature environments. Silicone Conformal Coating
(422A) is a flexible finish product that provides a protective coating
for printed circuit boards against moisture, corrosion, and thermal
shock. It protects and insulates electrical and electronic components
and assemblies, including generators, motors, transformers, relays, and
solenoid coils. For spraying, liquid can be thinned using M.G. Thinner
Cleaner. Thin up to one half part thinner to one part coating. Also
available in a micro tip pen format.
==============

I'd remove the board, clean it by pouring some drug-store alcohol over
it while scrubbing it with a soft brush, let it dry completely and then
apply the coating.

If the board is relatively clean, then maybe just turn off power the the
AC unit and spray the board with the coating without taking it out.

I looked at the info on these coatings. They need to be baked on after
application.
There are also catalyzed or self curing coatings.Master bond has UV
cure coatings.

MG's product will room temperature cure in 48 hours, or it can be
heated to speed it up.
Dow Corning makes Room Temperature Vulcanizing elastomeric and
Elastoplastic as well as solventless heat cured products.
Nordson also produces UV, Heat, and Air Dry products.

[Paul Drahn]

On 11/16/2011 2:45 PM, Michael Dobony wrote:
I have an all-in-one AC/furnace sitting outside. The circuit board was
replaced a very short time ago, about two months ago. It is already showing
signs of degradation (rust on a diode lead). Is there any spray coating I
can put on this to prevent further degradation, assuming it is still in
operating condition?

This is a link to the type of unit I have
http://www.americanstandardair.com/P...ckaged+Systems

Mike D.
Mike,
Rust on diode leads is quite surprising as even the high current diodes
with steel wire leads have a solder coating (tinned leads). Perhaps the
leads were damaged during assembly or testing and the coating was broken.

If you can turn the power off and get to the leads, I would suggest
cleaning off the rust and retinning the leads with a soldering iron and
rosin core solder.

I had our heat pump serviced last week and watched the young man as he
did his work. The circuit board controller is like yours, outside on the
heat pump and and under a metal cover that protects it from all but
blowing snow. Quite a bit of dust, but no other problems. The board does
have three 2 watt resistors that have discolored the board from their
heat. They should have been placed further from the board material.

Such heat producing devices are one good reason not to conformal coat
the circuit board. Or they need to be masked so coating material is kept
away from the resistors.

My electronic assembly company is required to conformal coat several
different circuit boards. In most cases we use urethane applied with a
brush and carefully avoid the locations the customer wants to not be
coated. Connectors, switches, sensors, test points, and mounting holes.

Other customers have specified the silicon based coating. Both coating
material is rather expensive. Much of it is ONLY available in metal one
gallon cans because bottles can't be shipped UPS. Urethane is available
in spray cans, but most cans are plugged up and won't spray, even right
from the distributor. Shelf life is almost zero. There is no return on
conformal coating material.

Paul

[Tony Hwang]

Paul Drahn wrote:
On 11/16/2011 2:45 PM, Michael Dobony wrote:
I have an all-in-one AC/furnace sitting outside. The circuit board was
replaced a very short time ago, about two months ago. It is already
showing
signs of degradation (rust on a diode lead). Is there any spray coating I
can put on this to prevent further degradation, assuming it is still in
operating condition?

This is a link to the type of unit I have
http://www.americanstandardair.com/P...ckaged+Systems


Mike D.
Mike,
Rust on diode leads is quite surprising as even the high current diodes
with steel wire leads have a solder coating (tinned leads). Perhaps the
leads were damaged during assembly or testing and the coating was broken.

If you can turn the power off and get to the leads, I would suggest
cleaning off the rust and retinning the leads with a soldering iron and
rosin core solder.

I had our heat pump serviced last week and watched the young man as he
did his work. The circuit board controller is like yours, outside on the
heat pump and and under a metal cover that protects it from all but
blowing snow. Quite a bit of dust, but no other problems. The board does
have three 2 watt resistors that have discolored the board from their
heat. They should have been placed further from the board material.

Such heat producing devices are one good reason not to conformal coat
the circuit board. Or they need to be masked so coating material is kept
away from the resistors.

My electronic assembly company is required to conformal coat several
different circuit boards. In most cases we use urethane applied with a
brush and carefully avoid the locations the customer wants to not be
coated. Connectors, switches, sensors, test points, and mounting holes.

Other customers have specified the silicon based coating. Both coating
material is rather expensive. Much of it is ONLY available in metal one
gallon cans because bottles can't be shipped UPS. Urethane is available
in spray cans, but most cans are plugged up and won't spray, even right
from the distributor. Shelf life is almost zero. There is no return on
conformal coating material.

Paul

Hi,
Orientation of board is important as well. Right side up, on vert. vs.
horiz. plane exposure to the element or under ventilated cover, etc.

[harry]

On Nov 16, 11:51*pm, "Stormin Mormon"
wrote:
WD-40 comes to mind. But, is it a water displacer, or a
lubricant? The myseries of the universe.

--
Christopher A. Young
Learn more about Jesus
*www.lds.org
.


Yes WD40 is the thing.

[Michael Dobony]

On Wed, 16 Nov 2011 20:17:09 -0800, mike wrote:

Michael Dobony wrote:
On Wed, 16 Nov 2011 16:04:27 -0800, mike wrote:

Home Guy wrote:
Michael Dobony wrote:

I have an all-in-one AC/furnace sitting outside. The circuit board
was replaced a very short time ago, about two months ago. It is
already showing signs of degradation (rust on a diode lead).
Is there any spray coating I can put on this to prevent further
degradation, assuming it is still in operating condition?
What will probably do the job is something called "conformal coating".

Here's one example:

http://www.mgchemicals.com/products/422a.html

==============
Silicone Conformal Coating

Ideal for high temperature environments. Silicone Conformal Coating
(422A) is a flexible finish product that provides a protective coating
for printed circuit boards against moisture, corrosion, and thermal
shock. It protects and insulates electrical and electronic components
and assemblies, including generators, motors, transformers, relays, and
solenoid coils. For spraying, liquid can be thinned using M.G. Thinner
Cleaner. Thin up to one half part thinner to one part coating. Also
available in a micro tip pen format.
==============

I'd remove the board, clean it by pouring some drug-store alcohol over
it while scrubbing it with a soft brush, let it dry completely and then
apply the coating.

If the board is relatively clean, then maybe just turn off power the the
AC unit and spray the board with the coating without taking it out.
In any repair situation, it's important to fix the thing that's broke.
Any product designed to sit outside MUST be capable of withstanding
the environment. Unless you're near an ocean, your environment is likely
way less corrosive than the design/test environment.

I'd call the vendor or the installer and see what they have to say about it.
Then I'd look at how the board is configured and make sure the enclosure
isn't missing a gasket, or bent, or has an open screw hole in it.
Seal it up tight. Make sure it's dry inside when you're done.

LOL!!!!! The panel covering it is held on with two screws and the cover has
no gasket and is ventilated to the outside. It experiences the same
atmospheric conditions as exist outside, like an open porch with open
horizontal blind style windows. To seal it up also would seal up the air
from the furnace burner.

Sounds like you've got a very bad design, or have installed an "inside"
box outside where it doesn't belong.
What does the vendor/installer say about it?

Bad design and $5,000 to put in a new one that might have a better design.
It belongs outside. Take a look at the link.


Conformal coating seems attractive on the surface.
Of course, it's gonna void the warranty and make the board very difficult
to repair.
It has thermal resistance, so any component depending on convection
cooling will be compromised.

If you decide to clean it, be aware that some components may not like
being drenched in alcohol and water.

Spraying the board in place may not be effective. You need to seal
the back and the edges of the board.

If you decide to coat it, dry it as discussed above, then dry it again.
Doesn't do a lot of good to keep out the water when the water's already
under the coating.

Still think I'd seal the enclosure first.

Total reengineering and moving the board to a totally new location.

[Michael Dobony]

On Wed, 16 Nov 2011 22:32:33 -0700, Tony Hwang wrote:

Paul Drahn wrote:
On 11/16/2011 2:45 PM, Michael Dobony wrote:
I have an all-in-one AC/furnace sitting outside. The circuit board was
replaced a very short time ago, about two months ago. It is already
showing
signs of degradation (rust on a diode lead). Is there any spray coating I
can put on this to prevent further degradation, assuming it is still in
operating condition?

This is a link to the type of unit I have
http://www.americanstandardair.com/P...ckaged+Systems


Mike D.
Mike,
Rust on diode leads is quite surprising as even the high current diodes
with steel wire leads have a solder coating (tinned leads). Perhaps the
leads were damaged during assembly or testing and the coating was broken.

If you can turn the power off and get to the leads, I would suggest
cleaning off the rust and retinning the leads with a soldering iron and
rosin core solder.

I had our heat pump serviced last week and watched the young man as he
did his work. The circuit board controller is like yours, outside on the
heat pump and and under a metal cover that protects it from all but
blowing snow. Quite a bit of dust, but no other problems. The board does
have three 2 watt resistors that have discolored the board from their
heat. They should have been placed further from the board material.

Such heat producing devices are one good reason not to conformal coat
the circuit board. Or they need to be masked so coating material is kept
away from the resistors.

My electronic assembly company is required to conformal coat several
different circuit boards. In most cases we use urethane applied with a
brush and carefully avoid the locations the customer wants to not be
coated. Connectors, switches, sensors, test points, and mounting holes.

Other customers have specified the silicon based coating. Both coating
material is rather expensive. Much of it is ONLY available in metal one
gallon cans because bottles can't be shipped UPS. Urethane is available
in spray cans, but most cans are plugged up and won't spray, even right
from the distributor. Shelf life is almost zero. There is no return on
conformal coating material.

Paul

Hi,
Orientation of board is important as well. Right side up, on vert. vs.
horiz. plane exposure to the element or under ventilated cover, etc.

Vertical orientation. The old board had rust running down from one
connection to the next, about five or six connections gone. It was in there
two years unused. Now I have freezing weather and can't wait for shipped
unit. If I have to replace it again it will cost double what I can find on
the internet.

[gregz]

Paul Drahn wrote:
On 11/16/2011 6:42 PM, mike wrote:
Ron wrote:
On Nov 16, 8:03 pm, gregz wrote:

That being said, sometimes after I wash electronics with water, Then
spray
with wd40, and continue drying with heat.

What electronics do you wash with water?

Much of the electronics in the world has been washed in water as
part of the assembly process.
There are components that can't stand it, so you gotta be careful.
I wash circuit boards in Simple Green cleaner, then alcohol then water
then do it again. Blow off the water with compressed air between washes,
then repeat again. Some gunk is soluble in simple green, some in alcohol,
you need both.
Scrub with a toothbrush at every stage.
Doesn't do much good to dissolve the stuff then let the solvent evaporate.
Blowing off is critical to the process. Get all the liquid out from
under parts. Space under a surface mount IC can be tiny.
Dry it then dry it again then dry it some more.
Works wonders on removing residue from leaky electrolytic capacitors.

Some people use the dishwasher. I don't because It's harder to mask
components that can't be washed.
General rules of thumb include:
1)don't get solvent into anything that changes properties under the
influence.
2)don't get solvent into electromechanical stuff.
3)don't get solvent into anything that it can't easily get out of.
It's really easy to let contaminated solvent seep into a switch, but
it's very
difficult to get it ALL out. Evaporation is not an option, cause
the process deposits more gunk and leaves it behind.
That's what we do. Wash all boards with hot deionized water in a
commercial board washer. I think the temp is around 140 degrees F. Looks
like a very expensive dish washer. All water is recirculated through
tanks to clean and deionize the water. We have a regular Sears dish
washer for backup and that water goes down the drain.

After the washer tries to dry the boards, the excess water is blown off
using deionized compressed air, being extra careful to clear all water
from under components. After that, they are air dried for a while.

All components that can't be washed are hand added after washing. Flux
from that operation is cleaned with IPA, isopropal alcohol. Sometimes a
manufacturer fails to state on their component spec sheet that the unit
can't be washed and then there is trouble, but most do tell you.

Paul

Had some problems with some German caps that were not totally sealed. From
the board manufacturer had leakage that didn't work with the circuit which
did not tolerate leakage. Had to replace each by hand. Even had board
leakage under components. Switched to another type cap and got better
washings, problems went away.

Deionized compressed air. I like that one. I think my solder station had
that, and heated with temperature settings. Often used 100 watt bulb to
bake boards.



Greg

[gregz]

wrote:
On Wed, 16 Nov 2011 18:51:35 -0500, "Stormin Mormon"
wrote:

WD-40 comes to mind. But, is it a water displacer, or a
lubricant? The myseries of the universe.
And not worth squat as a circuit board protector. Might want to try
LPS2 - but at best it is also only a temporaty protection - and it
holds dirt etc.


Ever try LPS3 ? Waxy coating, but sticky.

Greg


Like I said before - silicone conformal coating - applied to a CLEAN
board when new.

[gregz]

Ron wrote:
On Nov 16, 8:03 pm, gregz wrote:

That being said, sometimes after I wash electronics with water, Then spray
with wd40, and continue drying with heat.

What electronics do you wash with water?

Most anything that might have salt, coke, orange juice, etc. ASAP.
Many electronics boards are washed to remove contaminants, sometimes in the
dish washer. Today's boards mostly need water to flush the water based
flux.

Greg

[Ron]

On Nov 17, 7:46*pm, gregz wrote:
Ron wrote:
On Nov 16, 8:03 pm, gregz wrote:

That being said, sometimes after I wash electronics with water, Then spray
with wd40, and continue drying with heat.

What electronics do you wash with water?

Most anything that might have salt, coke, orange juice, etc. ASAP.


In that case, I need to put my keyboard in the dishwasher G

[gregz]

Michael Dobony wrote:
On Wed, 16 Nov 2011 22:32:33 -0700, Tony Hwang wrote:

Paul Drahn wrote:
On 11/16/2011 2:45 PM, Michael Dobony wrote:
I have an all-in-one AC/furnace sitting outside. The circuit board was
replaced a very short time ago, about two months ago. It is already
showing
signs of degradation (rust on a diode lead). Is there any spray coating I
can put on this to prevent further degradation, assuming it is still in
operating condition?

This is a link to the type of unit I have
http://www.americanstandardair.com/P...ckaged+Systems


Mike D.
Mike,
Rust on diode leads is quite surprising as even the high current diodes
with steel wire leads have a solder coating (tinned leads). Perhaps the
leads were damaged during assembly or testing and the coating was broken.

If you can turn the power off and get to the leads, I would suggest
cleaning off the rust and retinning the leads with a soldering iron and
rosin core solder.

I had our heat pump serviced last week and watched the young man as he
did his work. The circuit board controller is like yours, outside on the
heat pump and and under a metal cover that protects it from all but
blowing snow. Quite a bit of dust, but no other problems. The board does
have three 2 watt resistors that have discolored the board from their
heat. They should have been placed further from the board material.

Such heat producing devices are one good reason not to conformal coat
the circuit board. Or they need to be masked so coating material is kept
away from the resistors.

My electronic assembly company is required to conformal coat several
different circuit boards. In most cases we use urethane applied with a
brush and carefully avoid the locations the customer wants to not be
coated. Connectors, switches, sensors, test points, and mounting holes.

Other customers have specified the silicon based coating. Both coating
material is rather expensive. Much of it is ONLY available in metal one
gallon cans because bottles can't be shipped UPS. Urethane is available
in spray cans, but most cans are plugged up and won't spray, even right
from the distributor. Shelf life is almost zero. There is no return on
conformal coating material.

Paul

Hi,
Orientation of board is important as well. Right side up, on vert. vs.
horiz. plane exposure to the element or under ventilated cover, etc.

Vertical orientation. The old board had rust running down from one
connection to the next, about five or six connections gone. It was in there
two years unused. Now I have freezing weather and can't wait for shipped
unit. If I have to replace it again it will cost double what I can find on
the internet.

I would normally talk to company for possible fixes. Sometimes we have to
try to get the company to do a fix. They like a certain amount of repair in
their products.
Even if board is good, connectors will still have problems.

Greg

[gregz]

Ron wrote:
On Nov 17, 7:46 pm, gregz wrote:
Ron wrote:
On Nov 16, 8:03 pm, gregz wrote:

That being said, sometimes after I wash electronics with water, Then spray
with wd40, and continue drying with heat.

What electronics do you wash with water?

Most anything that might have salt, coke, orange juice, etc. ASAP.


In that case, I need to put my keyboard in the dishwasher G

Honestly, if I dropped a soda on something like that, I would immediately
drop an equal or more amount of water over the same area. This would not go
over too well doing a gig.

Greg

[larry moe 'n curly]

Michael Dobony wrote:

I have an all-in-one AC/furnace sitting outside. The circuit board was
replaced a very short time ago, about two months ago. It is already showing
signs of degradation (rust on a diode lead). Is there any spray coating I
can put on this to prevent further degradation, assuming it is still in
operating condition?

This is a link to the type of unit I have
http://www.americanstandardair.com/P...ckaged+Systems

All our A/Cs have been packaged systems, but I don't think their
circuit boards ever rusted much, although we're in Phoenix. I saw
only one of their circuit boards, a defrost controller, and I don't
believe it had any protective coating on it. So is it possible your
board wasn't grounded adequately? Or would it help to attach its
chassis ground to some zinc, even just galvanized screws?

[willshak]

Ron wrote the following:
On Nov 17, 7:46 pm, gregz wrote:
Ron wrote:
On Nov 16, 8:03 pm, gregz wrote:
That being said, sometimes after I wash electronics with water, Then spray
with wd40, and continue drying with heat.
What electronics do you wash with water?
Most anything that might have salt, coke, orange juice, etc. ASAP.


In that case, I need to put my keyboard in the dishwasher G


Where I used to work, I was in charge of the computer system, among
other things.
(not programming or repair, just in charge of the personnel and computer
purchase)
People used to drink coffee or tea, or even eat while at the computer
spilling all sorts of stuff on the keyboards. When this happened, I just
replaced the keyboard. I took the old keyboard into the lunch room and
flooded it with warm water and hung it to dry. When dry, I tested it and
if it worked, returned it to the replaceable keyboard stack.


--

Bill
In Hamptonburgh, NY
In the original Orange County. Est. 1683
To email, remove the double zeroes after @

[Stormin Mormon]

You're not a government worker? that makes
too much sense.

Great way to save money, and materials.

Roughly, how many keyboards were saved,
versus trashed? Did you save half of them?

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"willshak" wrote in message
m...

Where I used to work, I was in charge of the
computer system, among other things. (not
programming or repair, just in charge of the
personnel and computer purchase)

People used to drink coffee or tea, or even eat
while at the computer spilling all sorts of stuff
on the keyboards. When this happened, I just
replaced the keyboard. I took the old keyboard
into the lunch room and flooded it with warm
water and hung it to dry. When dry, I tested it
and if it worked, returned it to the replaceable
keyboard stack.


--

Bill
In Hamptonburgh, NY
In the original Orange County. Est. 1683
To email, remove the double zeroes after @