junebug1701 wrote in message
...
On Jul 13, 8:42 am, "N_Cook" wrote:
Used for fixing otherwise floppy bits to boards.
Is it hygroscopic ? whatever the word is, but pulls dampness out of the
air.
Beocenter 4000 from 1985 with the LC7815 (not V reg) electronic 2 pole 4
way
switch, internally locked into Aux only input, so disabling everything
else.
0.7 inch pitch 28 pin DIP but now removed and replacement available.
Affected input was on one side of the IC and some of this ****ty brown
stuff
on the other.

Nigel, from my experience this brown glue eventually turns dark brown,
and when it does it becomes conductive. I have found it difficult to
remove. A plastic serrated knife like you might find in a take-away
food box works well and is soft enough not to damage the traces on the
board. I really hate that glue.

James

On first sighting of this latest case, I tested the glue and it was more
than 30 Megs , just retested a bit and over 500 megs.

I suspect the plain gummy petroleum glue is ok over time, but it is a
problem with a filler/bulking agent used. I agree it goes brown with age,
perhaps it is something like corn flour or vegetative starch as filler. I
doubt a mineral like talcum or French chalk, as a filler, would go this very
dark brown or be a problem. The recent failure was due to corrossion
localised to where this glue had glooped over a few pins. Those pins looked
ok but after removal I could see corrosion and one of the pins, without the
pcb support, has almost sheared off due to the underlying corrosion.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/