Removing rubbery potting compound
Sam Goldwasser
eraser, maybe a bit tougher. It can be removed laboriously with knives,
picks, and elbow grease. But the question is whether there is some easier
way to do this that would leave the underlying components undamaged.
This stuff is used in a variety of places including PCBs and laser
tube assemblies. Both of these are of interest to me. Modest heat
has no effect including immersing in boiling water - it's not hot-melt glue.
Thanks!
--
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Lostgallifreyan
news:6wws755...@ampersand.seas.upenn.edu:
> This type is usually dark gray and soft - about the consistency of a
> pencil eraser, maybe a bit tougher. It can be removed laboriously with
> knives, picks, and elbow grease. But the question is whether there is
> some easier way to do this that would leave the underlying components
> undamaged. This stuff is used in a variety of places including PCBs and
> laser tube assemblies. Both of these are of interest to me. Modest
> heat has no effect including immersing in boiling water - it's not
> hot-melt glue.
>
I think you need a tin of grey rubbery stuff remover.
William Sommerwerck
Go back to your TARDIS.
Sam Goldwasser
HeHeHe... Do you charge BIG BUCKs for that advice, huh? :)
And, it probably rots internal organs.....
N_Cook
news:6wws755...@ampersand.seas.upenn.edu...
I seem to remember using a 1/8 inch ball mill in a Dremmel for that sort of
stuff, localised heat and tugging action hepled in removing from surfaces,
. But still time consuming and you have to know there is no little vital
stuff buiried within it.
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
Lostgallifreyan
> Lostgallifreyan <no-...@nowhere.net> writes:
>
>> Sam Goldwasser <s...@ampersand.seas.upenn.edu> wrote in
>> news:6wws755...@ampersand.seas.upenn.edu:
>>
>>> This type is usually dark gray and soft - about the consistency of a
>>> pencil eraser, maybe a bit tougher. It can be removed laboriously with
>>> knives, picks, and elbow grease. But the question is whether there is
>>> some easier way to do this that would leave the underlying components
>>> undamaged. This stuff is used in a variety of places including PCBs and
>>> laser tube assemblies. Both of these are of interest to me. Modest
>>> heat has no effect including immersing in boiling water - it's not
>>> hot-melt glue.
>>>
>>
>> I think you need a tin of grey rubbery stuff remover.
>
> HeHeHe... Do you charge BIG BUCKs for that advice, huh? :)
Oh yeah, I should, given what anything seems to cost the moment I need it...
Here's some for free though. Try snagging a bit and burning it, melting it,
putting it in chemicals, and comparing to some knowns. If it's silicone
you're SOL but a lot of other stuff might be attacked while the rest of the
parts sit looking as if they enjoy it because a lot of PCB washes are strong
stuff and most parts are designed to resist a lot. If you find something that
can edge its way between the stuff and the parts, you might be able to peel
it off. And if it's based on actual rubber try ozone to perish it fast so it
will crumble away.
>
> And, it probably rots internal organs.....
>
And what did you think the grey goop was made of? >:) Thpthpthp (That being
my best Hannibal Lecter impersonation, feeble though it may be).
Lostgallifreyan
news:Xns9C31E597F72...@216.196.109.145:
> And if it's based on actual rubber try ozone to perish it fast so it
> will crumble away.
>
Likewise, strong shortwave UV might also help degrade it so it's easy to
remove.
Lostgallifreyan
news:h1m3kv$pp3$1...@news.eternal-september.org:
>> I think you need a tin of grey rubbery stuff remover.
>
> Go back to your TARDIS.
>
>
>
I would but I don't think it will have me.
Sam Goldwasser
> Sam Goldwasser <s...@ampersand.seas.upenn.edu> wrote in message
> news:6wws755...@ampersand.seas.upenn.edu...
>> This type is usually dark gray and soft - about the consistency of a
> pencil
>> eraser, maybe a bit tougher. It can be removed laboriously with knives,
>> picks, and elbow grease. But the question is whether there is some easier
>> way to do this that would leave the underlying components undamaged.
>> This stuff is used in a variety of places including PCBs and laser
>> tube assemblies. Both of these are of interest to me. Modest heat
>> has no effect including immersing in boiling water - it's not hot-melt
> glue.
>>
>> Thanks!
>>
>> --
>> sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
>
> I seem to remember using a 1/8 inch ball mill in a Dremmel for that sort of
> stuff, localised heat and tugging action hepled in removing from surfaces,
> . But still time consuming and you have to know there is no little vital
> stuff buiried within it.
I've been using the mechanical approach. It is tedious and risky as
you note. But does work:
http://repairfaq.cis.upenn.edu/Misc/vmi373p1.jpg
However, some components were damaged (a graphics editing program
can work wonders!) and for what I really want, it is trickier
as the part being removed is a glass laser tube and much of the
potting material is in a space 2 or 3 mm thick surrounding the
tube, and running its entire length.
Thanks!
--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
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> --
o...@uakron.edu
Eposolve, mcmaster carr is your friend.
Steve
James Sweet
> This type is usually dark gray and soft - about the consistency of a pencil
> eraser, maybe a bit tougher. It can be removed laboriously with knives,
> picks, and elbow grease. But the question is whether there is some easier
> way to do this that would leave the underlying components undamaged.
> This stuff is used in a variety of places including PCBs and laser
> tube assemblies. Both of these are of interest to me. Modest heat
> has no effect including immersing in boiling water - it's not hot-melt glue.
>
> Thanks!
>
The best luck I've had is with simply picking the stuff off, you're
right though that it's no fun. I suspect it would become brittle at some
temperature, can you get your hands on some liquid nitrogen? If so, give
it a soak and smack it with something, hoping the components within do
not shatter as well. I'm curious to hear the results.
heruursciences
The rubbery tarry stuff that is used in older hene tube heads
dissolves in dichloromethane (DCM) used in paint strippers, The
silicone stuff is pretty impervious to all but mechanical attack.
N_Cook
What is the output level of the Cockcroft Walton circuit ?
Mike Harrison
Although DCM is pretty effective, it also dissolves PCB material, resistor/capacitor coatings, LEDs
and many other plastics, so is of limited use.
Incidentally on that pic of the HeNe laser PSU, I wonder why they left the resist off the HV section
of the board - better adhesion perhaps?
Adrian C
> The rubbery tarry stuff that is used in older hene tube heads
> dissolves in dichloromethane (DCM) used in paint strippers, The
> silicone stuff is pretty impervious to all but mechanical attack.
FWIW There is a home decorating product called 'silicone eater' designed
for removing sealant from hard surfaces by dissolving it a little.
<http://www.cglass.co.uk/everbuild-everflex-silicone-eater-pr-17657.html>
--
Adrian C
Bruce Esquibel
> This type is usually dark gray and soft - about the consistency of a pencil
> eraser, maybe a bit tougher. It can be removed laboriously with knives,
> picks, and elbow grease. But the question is whether there is some easier
> way to do this that would leave the underlying components undamaged.
> This stuff is used in a variety of places including PCBs and laser
> tube assemblies. Both of these are of interest to me. Modest heat
> has no effect including immersing in boiling water - it's not hot-melt glue.
This probably isn't much help but we used to use a chemical called
Eccostrip 93 made by Emerson and Cuming (or cumming or cummings).
I don't know if it's sold anymore, probably on every EPA hazard chemical
list by now but I believe the main purpose of it was to attack something in
the resin.
It wasn't a miracle worker, but did it's job eventually. Generally you
needed to apply it with a glass eyedropper to keep the area wet, then
periodically using a acid brush, dust off the powder, reapply.
As far as component damage, yeah, some carbon film resistors, the bodies
would flake off but I don't remember anything else. Even ic's (chips) that I
thought had some epoxy holding them together were no worse for wear even
soaking in the stuff.
-bruce
b...@ripco.com
Sam Goldwasser
That might work for the PCBs, though what will it do to the components?
However, what I really need to remove it from are special HeNe laser tube
assemblies. Not the common laser heads, but ones where the tube is totally
surrounded by the stuff as well as in front and back. So, the tube will
still be stuck inside surrounded by brittle hard stuff. :)
Thanks for thinking about it!
Sam Goldwasser
> What is the output level of the Cockcroft Walton circuit ?
Greater than 10 kV but the current is very low since it only needs to drive
an open circuit, then is bypassed once the main current flows. Nearly
every HeNe laser power supply has a circuit like that.
--
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William Sommerwerck
easily removed, especially by chemical means. Otherwise, there would be
little point to it.
Sam Goldwasser
Yeah, for the real application I have in mind, this is probably going to
take about 1,423 years (give or take a century). :)
The PCB was just an example. But where this is needed is to remove
the stuff surrounding a glass laser tube - about 6 inches in length
and a space of 2 or 3 mm between the tube and the cylinder it's in.
Both the cylinder and tube need to come out undamaged.
Thanks.
--
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> -bruce
> b...@ripco.com
PeterD
<s...@ampersand.seas.upenn.edu> wrote:
>This type is usually dark gray and soft - about the consistency of a pencil
>eraser, maybe a bit tougher. It can be removed laboriously with knives,
>picks, and elbow grease. But the question is whether there is some easier
>way to do this that would leave the underlying components undamaged.
>This stuff is used in a variety of places including PCBs and laser
>tube assemblies. Both of these are of interest to me. Modest heat
>has no effect including immersing in boiling water - it's not hot-melt glue.
>
>Thanks!
Go to a good hardware store, and see if they have silicone tub caulk
remover. Try that and see if it works.
N_Cook
news:6wk5348...@minus.seas.upenn.edu...
Can you make a pilot hole with a thin steel rod, chisel ground at the end.
Then pass through it one of those carbide covered wire saw , garotte type
things, or even a coping saw blade, kept under tension. Would some scratch
damage matter? If so then perhaps spaced , glued-on, guard rings along the
blade
N_Cook
news:h1o157$2bo$1...@news.eternal-september.org...
or after a pilot hole then a current carrying length of straightened heater
element wire perhaps would work to cut around
Rich Webb
Maybe one of the oscillating-face tools, like the Fein MultiMaster?
http://www.fein.de/fein-multimaster/us/en/main/
There are flexible blades that might do the trick. Won't work (very
well) to de-pot an SMT-stuffed PCB but might get you a long way towards
getting the stuff off of the tube.
<http://www.fein.de/fein-multimaster/us/en/products/accessories_scraping.php>
--
Rich Webb Norfolk, VA
David Nebenzahl
> Maybe one of the oscillating-face tools, like the Fein MultiMaster?
> http://www.fein.de/fein-multimaster/us/en/main/
Don't think so; those tools work on a principle that's the complete
opposite of what is needed here. That is, they'll cut something hard but
not damage something soft next to it, like the saws used for cutting off
plaster casts that don't harm skin. They'll just jiggle the rubbery
stuff without cutting it.
How about careful use of a cutoff wheel in a Dremel or equivalent tool,
to make slices in the rubbery stuff?
[note post trimming]
--
Found--the gene that causes belief in genetic determinism
Rich Webb
<nob...@but.us.chickens> wrote:
>On 6/22/2009 7:16 AM Rich Webb spake thus:
>
>> Maybe one of the oscillating-face tools, like the Fein MultiMaster?
>> http://www.fein.de/fein-multimaster/us/en/main/
>
>Don't think so; those tools work on a principle that's the complete
>opposite of what is needed here. That is, they'll cut something hard but
>not damage something soft next to it, like the saws used for cutting off
>plaster casts that don't harm skin. They'll just jiggle the rubbery
>stuff without cutting it.
Roger that. However, from watching the infomercial it looks like the
flexible, spatulate heads are used to separate stuff like caulk beads
from porcelain bathtubs. The working face isn't toothed and might just
do the trick in this app.
I don't speak from personal experience, just what I've seen on the tube.
But, since "He who dies with the most tools, wins!" I'll probably have
to break down someday and get one.
Sam Goldwasser
I think that's only true in some cases. Since this CAN be removed
using just brute force, it's a lot easier to reverse engineer
PCBs and such with it than, say, hard Epoxy.
--
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Sam Goldwasser
>> > -bruce
>> > b...@ripco.com
>
> Can you make a pilot hole with a thin steel rod, chisel ground at the end.
> Then pass through it one of those carbide covered wire saw , garotte type
> things, or even a coping saw blade, kept under tension. Would some scratch
> damage matter? If so then perhaps spaced , glued-on, guard rings along the
> blade
That's sort of what I've been doing, and have been contemplating making
a tool that is more matched to the job than the strips of aluminum and
other random items I've been using.
I'm coming to believe that any chemical approach will take to long, not
to mention the mess and health issues.
--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
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| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html
Important: Anything sent to the email address in the message header above is
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> --
Sam Goldwasser
Could be. The only real problem is getting the tube out. Once it's out,
getting the stuff off of it and the cylinder it was in is no problem,
the adhesion is not very strong, just enough that you can't push the
tube out without likely smashing it.
Thanks!
--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Lostgallifreyan
> The only real problem is getting the tube out. Once it's out,
> getting the stuff off of it and the cylinder it was in is no problem,
> the adhesion is not very strong, just enough that you can't push the
> tube out without likely smashing it.
So do it the way a capacitor is removed from the PFN for the SSY-1. Use a
fast cutting disk, or slow hacksaw, to cut the outer cylinder parallel to
axis, peel it back enough to remove the innards, then peel the gunk off the
internal cylinder (cap, or laser in this case).
Michael Anton
"Sam Goldwasser" <s...@ampersand.seas.upenn.edu> wrote in message
news:6wws755...@ampersand.seas.upenn.edu...
> pencil
> eraser, maybe a bit tougher. It can be removed laboriously with knives,
> picks, and elbow grease. But the question is whether there is some easier
> way to do this that would leave the underlying components undamaged.
> This stuff is used in a variety of places including PCBs and laser
> tube assemblies. Both of these are of interest to me. Modest heat
> has no effect including immersing in boiling water - it's not hot-melt
> glue.
>
>
If it is silicone based, you might try Varsol. It causes one part silicone
to swell and get even more rubbery, so maybe it will behave similiarly
on that stuff. It tends to be easier to remove in this state.
Mike
James Sweet
>
> That might work for the PCBs, though what will it do to the components?
>
> However, what I really need to remove it from are special HeNe laser tube
> assemblies. Not the common laser heads, but ones where the tube is totally
> surrounded by the stuff as well as in front and back. So, the tube will
> still be stuck inside surrounded by brittle hard stuff. :)
>
> Thanks for thinking about it!
>
>
That sounds like a real pain. If you can use a long drill to drill a
tunnel parallel to the tube, you might be able to saw around the tube
with some piano wire.
James Sweet
> "William Sommerwerck" <grizzle...@comcast.net> writes:
>
>> Whatever this stuf is, common sense suggests it was designed not to be
>> easily removed, especially by chemical means. Otherwise, there would be
>> little point to it.
>
>
> I think that's only true in some cases. Since this CAN be removed
> using just brute force, it's a lot easier to reverse engineer
> PCBs and such with it than, say, hard Epoxy.
>
Even hard epoxy is no real matter when it comes to reverse engineering
if you are willing to destroy the thing you are analyzing. I've found
that it's quite brittle stuff, and applying pressure in the right places
with a bench vise will usually cause it to crumble. Some components will
get broken in the process but they can usually still be identified.
N_Cook
news:6weitbx...@minus.seas.upenn.edu...
> Rich Webb <bbe...@mapson.nozirev.ten> writes:
>
> > On Mon, 22 Jun 2009 08:33:23 -0400, Sam Goldwasser
> > <s...@minus.seas.upenn.edu> wrote:
> >
> >>Bruce Esquibel <b...@ripco.com> writes:
> >>
> >>> In sci.electronics.repair Sam Goldwasser
<s...@ampersand.seas.upenn.edu> >
> getting the stuff off of it and the cylinder it was in is no problem,
> the adhesion is not very strong, just enough that you can't push the
> tube out without likely smashing it.
>
>
> Thanks!
>
> --- 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.
In that case would mounting a vacuum chamber around the outside give enough
force for air pressure to shift it. Or compressed air around it with
appropriate seal? With some nearby soft physical restraint of course for if
it does move.
Mike Harrison
..er why has nobody suggested cutting it out with... a LASER!
I'd imagine a few watts of CO2 would do it, although near-IR may be better at reducing the risk of
tube damage as the beam would be reflected.
JW
<s...@minus.seas.upenn.edu> wrote in Message id:
<6wk5348...@minus.seas.upenn.edu>:
>The PCB was just an example. But where this is needed is to remove
>the stuff surrounding a glass laser tube - about 6 inches in length
>and a space of 2 or 3 mm between the tube and the cylinder it's in.
>Both the cylinder and tube need to come out undamaged.
How about using a thin blade from a coping saw? Once you manage to slip it
all the way through the length of the cylinder it should work fairly well.
I don't think it'd damage the glass either.
Sam Goldwasser
That's what someone else did, but the important part is really the cylinder.
I'd like to get the tube out intact as well, but the solution of last
resort is to simply smash the tubes. Yes, I know, that's going to upset
the gods of dead lasers, but we'll see how the alternatives work out! :)
Thanks!
--
Sam Goldwasser
Yeah, that's been my thinking as well. I don't like chemicals and anything
that would get through several inches of the close-fitting cylinder would
almost certainly be rather ansty.
Whether a coping saw blade is optimal I don't know, but something that
can be forced through and then fastened at both ends with enough "teeth"
to be able to eat away at the rubber.
Thanks!
Samuel M. Goldwasser
What could be more appropriate than using a laser to cut another laser
free. :)
William Sommerwerck
news:h1pisl$4aj$2...@news.eternal-september.org...
Please note the adverb in my original post.
root
>
> Whether a coping saw blade is optimal I don't know, but something that
> can be forced through and then fastened at both ends with enough "teeth"
> to be able to eat away at the rubber.
>
> Thanks!
>
I've lost track of how long the laser tube is. If you can thread
dental floss along the length of the tube you can saw the tube
out with the floss.
N_Cook
news:4e7145psh26ir5dcr...@4ax.com...
My coping saw blades are only 6 inches long, I doubt they come any longer as
only intended for small light work.
After drilling a pilot hole I would try one of these sort of wire saws
http://www.ecamo.co.uk/product/webtex-commando-survival-wire-saw/265.html
fed through and then bodge fixed in a 12 inch hacksaw frame for rigidity.
Or straightened out bit of heater element wire
Ron
> JW <no...@dev.null> writes:
>
>> On Mon, 22 Jun 2009 08:33:23 -0400 Sam Goldwasser
>> <s...@minus.seas.upenn.edu> wrote in Message id:
>> <6wk5348...@minus.seas.upenn.edu>:
>>
>>> The PCB was just an example. But where this is needed is to remove
>>> the stuff surrounding a glass laser tube - about 6 inches in length
>>> and a space of 2 or 3 mm between the tube and the cylinder it's in.
>>> Both the cylinder and tube need to come out undamaged.
>> How about using a thin blade from a coping saw? Once you manage to slip it
>> all the way through the length of the cylinder it should work fairly well.
>> I don't think it'd damage the glass either.
>
> Yeah, that's been my thinking as well. I don't like chemicals and anything
> that would get through several inches of the close-fitting cylinder would
> almost certainly be rather ansty.
>
> Whether a coping saw blade is optimal I don't know, but something that
> can be forced through and then fastened at both ends with enough "teeth"
> to be able to eat away at the rubber.
Might I suggest a flexible wire saw such as this one:
http://www.vtarmynavy.com/commando-wire-saw.htm
or this
http://au.farnell.com/abrafile/250130/flexisaw-15-pack-of-2-blades-handles/dp/108078
Perhaps you could stretch the saw between two fixed vices having first
threaded the tube over it, then work it back and forth while rotating it
to cut throught the rubber compound.
Ron(UK)
Samuel M. Goldwasser
Interesting thought. At least that's something I have. :)
I have a feeling it is going to be something along those lines.
James Sweet
> JW <no...@dev.null> wrote in message
> news:4e7145psh26ir5dcr...@4ax.com...
>> On Mon, 22 Jun 2009 08:33:23 -0400 Sam Goldwasser
>> <s...@minus.seas.upenn.edu> wrote in Message id:
>> <6wk5348...@minus.seas.upenn.edu>:
>>
>>> The PCB was just an example. But where this is needed is to remove
>>> the stuff surrounding a glass laser tube - about 6 inches in length
>>> and a space of 2 or 3 mm between the tube and the cylinder it's in.
>>> Both the cylinder and tube need to come out undamaged.
>> How about using a thin blade from a coping saw? Once you manage to slip it
>> all the way through the length of the cylinder it should work fairly well.
>> I don't think it'd damage the glass either.
>
> My coping saw blades are only 6 inches long, I doubt they come any longer as
> only intended for small light work.
>
> After drilling a pilot hole I would try one of these sort of wire saws
> http://www.ecamo.co.uk/product/webtex-commando-survival-wire-saw/265.html
> fed through and then bodge fixed in a 12 inch hacksaw frame for rigidity.
>
> Or straightened out bit of heater element wire
>
Or a guitar string, the rough coily type.