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'[TECH] Potting removal'
2011\10\03@121333 by Joe Wronski

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Hi, I have a 400W motor controller that is in a metal box and it is potted.  I'm curious if there are techniques to remove the potting.  The box is approx 2"x2.5"x1".  The 2"x2.5" dimension is open and the potting is (up to) 1" deep.
Background: This is for a 24V 400W DC brushed motor on a ThinkMobility Funbike.  I've found little documentation on the bike.  The controller has input lines from pedelec and speed sensor, as well as a cable from the handlebar mounted "brain".  Wiring everything to the battery results in no lights on brain and no power to the motor.  I'm looking at generic controllers on eBay ranging from $32 to $60.  I don't currently have the tech shop or junkbox to just wire something up.

Joe

2011\10\03@143613 by M.L.

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On Mon, Oct 3, 2011 at 12:14 PM, Joe Wronski <spam_OUTjwronskiTakeThisOuTspamstillwatereng.net> wrote:
> Hi, I have a 400W motor controller that is in a metal box and it is
> potted.  I'm curious if there are techniques to remove the potting.  The
> box is approx 2"x2.5"x1".  The 2"x2.5" dimension is open and the potting
> is (up to) 1" deep.
> Background: This is for a 24V 400W DC brushed motor on a ThinkMobility
> Funbike.  I've found little documentation on the bike.  The controller
> has input lines from pedelec and speed sensor, as well as a cable from
> the handlebar mounted "brain".  Wiring everything to the battery results
> in no lights on brain and no power to the motor.  I'm looking at generic
> controllers on eBay ranging from $32 to $60.  I don't currently have the
> tech shop or junkbox to just wire something up.
>
> Joe W

Joe, is your goal to repair the motor controller?

--
Martin K.

2011\10\03@162930 by Electron

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Assuming you can still find it (it was recently banned from EU at least,
due to suspects of it being cancerous) you can use DCM (dichloromethane),
usually easily found in paint removers/strippers.

Regards,
Mario


At 18.14 2011.10.03, you wrote:
{Quote hidden}

>

2011\10\03@164654 by Bob Blick

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On Monday, October 03, 2011 10:29 PM, "Electron"  wrote:
>
> Assuming you can still find it (it was recently banned from EU at least,
> due to suspects of it being cancerous) you can use DCM (dichloromethane),
> usually easily found in paint removers/strippers.

This is good stuff, available locally here in California:

http://www.coppergreen.com/greensliquid.htm

Bob

-- http://www.fastmail.fm - One of many happy users:
 http://www.fastmail.fm/docs/quotes.html

2011\10\03@190304 by Joe Wronski

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On 10/3/2011 2:35 PM, M.L. wrote:
> On Mon, Oct 3, 2011 at 12:14 PM, Joe Wronski<.....jwronskiKILLspamspam@spam@stillwatereng.net>  wrote:
>> Hi, I have a 400W motor controller that is in a metal box and it is
>> potted.  I'm curious if there are techniques to remove the potting.  The
>> box is approx 2"x2.5"x1".  The 2"x2.5" dimension is open and the potting
>> is (up to) 1" deep.
>> Background: This is for a 24V 400W DC brushed motor on a ThinkMobility
>> Funbike.  I've found little documentation on the bike.  The controller
>> has input lines from pedelec and speed sensor, as well as a cable from
>> the handlebar mounted "brain".  Wiring everything to the battery results
>> in no lights on brain and no power to the motor.  I'm looking at generic
>> controllers on eBay ranging from $32 to $60.  I don't currently have the
>> tech shop or junkbox to just wire something up.
>>
>> Joe W
> Joe, is your goal to repair the motor controller?
>
Yes, repair or re-work.  At least get access to the power transistors and heat sink, for possible re-use.  If they're blown, at least I'd have a starting point for a new controller with the circuit board and heat sink.
Joe W

2011\10\03@195252 by Joe Wronski

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On 10/3/2011 4:46 PM, Bob Blick wrote:
> On Monday, October 03, 2011 10:29 PM, "Electron"  wrote:
>> Assuming you can still find it (it was recently banned from EU at least,
>> due to suspects of it being cancerous) you can use DCM (dichloromethane),
>> usually easily found in paint removers/strippers.
> This is good stuff, available locally here in California:
>
> http://www.coppergreen.com/greensliquid.htm
>
> Bob
>
Greensliquid seems to be based on  methylene chloride, which I don't know whether it is the same as dichloromethane, but it sounds similar.  I have some Ace Hardware liquid stripper with methylene chloride, so I'll try it.  Thanks Mario and Bob.
I guess I was looking for a magic bullet, but it seems I'll be experimenting with scraping away softened goo with a blade and / or brush.
Joe

2011\10\04@055214 by RussellMc

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> Greensliquid seems to be based on  methylene chloride, which I don't
> know whether it is the same as dichloromethane, but it sounds similar.
> I have some Ace Hardware liquid stripper with methylene chloride, so

Methylene Chloride works well on epoxy.
Maybe noaction at first but begins to craze in minutes.
Action can get quite violent - to the extent that delicate components
and wiring are liable to be destroyed.
I don't know if diluting it makes it less violent.

MeC said to be nasty stuff to inhale or to get on skin. Some say
carcinogenic, some don't. Prudent avoidance wise.
Warming epoxy to as high as comfortable may soften it - but may just
accelerate reaction rate :-).

Som people say you can use it under a layer of xxx to stop it
evaporating and keep vapors where they belong.

Don't recall what xxx is - may be water  or ?

Gargoyles - yep - seems to be water. Immiscible with water, and water
forms a layer on top.


           Russell

2011\10\04@121256 by Electron

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At 01.52 2011.10.04, you wrote:
>On 10/3/2011 4:46 PM, Bob Blick wrote:
>> On Monday, October 03, 2011 10:29 PM, "Electron"  wrote:
>>> Assuming you can still find it (it was recently banned from EU at least,
>>> due to suspects of it being cancerous) you can use DCM (dichloromethane),
>>> usually easily found in paint removers/strippers.
>> This is good stuff, available locally here in California:
>>
>> http://www.coppergreen.com/greensliquid.htm
>>
>> Bob
>>
>Greensliquid seems to be based on  methylene chloride, which I don't
>know whether it is the same as dichloromethane, but it sounds similar.  
methylene chloride is the same substance as dichloromethane, different name,
same thing:

http://en.wikipedia.org/wiki/Dichloromethane


>I have some Ace Hardware liquid stripper with methylene chloride, so
>I'll try it.  Thanks Mario and Bob.

You're welcome.


>I guess I was looking for a magic bullet, but it seems I'll be
>experimenting with scraping away softened goo with a blade and / or brush.
>Joe W
>

2011\10\07@100330 by Joe Wronski

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On 10/4/2011 12:12 PM, Electron wrote:
{Quote hidden}

Well, live and learn.  For instance I learned that what looked like a metal box was actually plastic, as the methylene chloride or acetone in the paint stripper dissolved the enclosure, leaving a block of potting and circuitry behind.  It also softened the wiring insulation causing it to puff up and bulge.  What seemed to be a heat sink insulator washed away.  A plastic round 8 pin connector survived.  Electrolytic capacitors have their outer plastic sleeves (the exposed parts of them) melting away.  The potting (probably epoxy?) is still there.  More patience with a dremel and other chemicals may have been the way to go.
I ended up ordering a new 24V 30A motor controller from a Senzhen vendor on eBay for about $30.  It will probably be November before I see it.   EBay item number 260857326542.
Joe W

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