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Black Glue Peril

P

Phil Allison

Jan 1, 1970
0
** Hi to all,

the dreaded " Yellow Glue" problem has been mentioned here a few times.

I have exactly the same problem, but the glue is now black instead - with a
KRK 'Rokit 5" powered monitor - from China of course. Both PCBs are
liberally covered in the stuff, more on the amplifier and PSU one.

Symptoms in my example were loud crackling and low volume - which
recovered when I wound the AC back to 160V !!

Seems you have to get every bit of it off to effect repair. Along the way
you will see corroded leads and PCB link wires - there is a 2.2kohm next
to the filter caps that is buried in the glue and needs replacing.

This is worse than the Yellow Glue problem as it becomes conductive in areas
that have no heat.

Could the black colouring be carbon ??


.... Phil
 
P

Phil Allison

Jan 1, 1970
0
"Gareth Magennis"
"Phil Allison"

That sounds more like an epoxy, maybe not the same stuff?

** It's the same horrible stuff - just black.

Time and a bit of heat turns it into rock.

But why would it need to be black anyway?


** IEC inlets, rocker switches, XLRs and metal back panels are commonly
black.

So it matches, when used to achieve an air seal around them, like in this
case.



.... Phil
 
N

N_Cook

Jan 1, 1970
0
That sounds more like an epoxy, maybe not the same stuff?
But why would it need to be black anyway? Just makes it more expensive than
uncloloured adhesive.

The flux cleaner I think just softens it, so it doesn't adhere as strongly
to the PCB. Arfa might be able to confirm or deny this.



Incidentally, I recently made my own black speaker glue (for fixing dust
caps) using Evostick and laser printer toner. Works a treat, and a damn
sight cheaper than this tiny tube of what is probably the same stuff.

http://www.saveltd.co.uk/jbl-professional-moyen-rs-3087-speaker-driver-cement-glue-4125-p.asp




Gareth.

So that makes it 3 different types that cause such problems.
The yellow glue stuff
The white softish conformal coating material that breaks down leaving a
distinctive oily film, plus corrossion/conduction problems
This black stuff now
Does no manufacturer do accelerated aging of these sorts of materials
before selling them
 
P

Phil Allison

Jan 1, 1970
0
"Arfa Daily"
No. It 'softens' it which then makes it become sort of 'plastic' so that
it can be peeled off the board without taking all the little surface mount
components with it




This is the sort of thing that I was doing before, but one day I got so
fed up of having to use such force that I started trying all the liquid
chemicals that I had, just in case. The Servisol 160 is my defluxer of
choice, and I have used it for many years. I sprayed some on the glue, and
left it for 5 minutes, and when I tried again to shift the stuff, it had
ceased being hard and I was able to peel it with a blunt scalpel. Make no
mistake, it still doesn't come off easily, but much easier than when it is
hard before treatment. Whether it would have the same effect on your black
stuff, though ... ??


** Servisol 160 is mixture of a few solvents including "naphtha" the magic
ingredient in WD-40.

http://www.crcind.com/wwwcrc/msds/UK20046-23.htm

It is also highly flammable and toxic - so it must do the job ....



.... Phil
 
W

William Sommerwerck

Jan 1, 1970
0
"Phil Allison" wrote in message
Just what do you think you are doing -- Dave ??

"I can feel my mind going, Dave. Thee is no question about it."
 
N

N_Cook

Jan 1, 1970
0
No. It 'softens' it which then makes it become sort of 'plastic' so that
it can be peeled off the board without taking all the little surface
mount components with it




This is the sort of thing that I was doing before, but one day I got so
fed up of having to use such force that I started trying all the liquid
chemicals that I had, just in case. The Servisol 160 is my defluxer of
choice, and I have used it for many years. I sprayed some on the glue,
and left it for 5 minutes, and when I tried again to shift the stuff, it
had ceased being hard and I was able to peel it with a blunt scalpel.
Make no mistake, it still doesn't come off easily, but much easier than
when it is hard before treatment. Whether it would have the same effect
on your black stuff, though ... ??

Arfa

Does your Servisol 160 say what its primary solvent constituent is ,
other than uninformitive "hydrocarbon solvent" ?
 
J

Jeff Layman

Jan 1, 1970
0
The main ingredients of
Electrolube Lead Free Flux Remover, different pricipal ingredient
CYCLOHEXANE 30-60%
PROPAN-2-OL 10-30%
1-METHOXY-2-PROPANOL 10-30%

Any chemists here?
So were you getting softening just by using petroleum as a solvent?

All the constituents are organic solvents. 1-methoxy-2-propanol is a
particularly good solvent used in paints and other materials. For
example, see here:
http://www.recochem.com.au/index.ph...ents_penetrants_general/item/methoxy_propanol
 
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