Adrian Tuddenham wrote in message
valid.invalid...
N_Cook wrote:
Adrian Tuddenham wrote in message
valid.invalid...
N_Cook wrote:
Obviously I've come acros melting/burning, starting from bad
connection
arcing , but not this amount of damage, so am requesting other
opinions.
A superfluity of mains fuses all ok, on 240V UK mains, 5 amp in
plug, 4
amp
chassis mounted and internal 5 amp all in series. Mains transformer
seems
right sort of primary and secondary resistance. All other internal
fuses
ok
and no other visually obvious problems.
Burning right thru the pcb for 1/2 inch around the L pin of the IEC,
melting
of the plastic of the IEC above the burning and even the linecord
plug
surrounding the L pin melting where heat conducted through the pin
presumably. Remainder of IEC receptacle distorted from heat but
holding
together.
[...]
I have come across some connector pairs purporting to be
IEC-compliant,
where the pins and the socket connections hardly touched. I submitted
them to Trading Standards and was told that both halves did comply
with
the specification - so you might have come across a similar problem to
that; and the fault may not be in the soldering.
Where the pins of the IEC chassis part go through the plastic there is
no
melting or burning but the linecord plug (softer plastic) shows signs of
melting around the line pin , no burning.
Some of those IEC chassis connectors are almost indestructible. I have
tried to melt one of the pins out of one with a soldering iron and it
simply would not move. I had to tear the rivetted tag off the back with
a vice, then file down the remains of the pin and punch it out.
I can quite believe that the items each side could be damaged by heat
but the connector in the middle would show no signs of burning.
So the initial problem not
mis-mating of IEC pins. Downstream problems , transformer, ps etc is
possible I suppose , no blown fuses though.
If the direct cause of the heat was a high resistance joint, you
wouldn't expect a blown fuse. A shorted secondary on a small
transformer wouldn't necessarily blow the fuse either.
It has occurred to me that if a solder joint had gone high resistance,
the increase in temperature would either melt it back together or blow
it open before the board became damaged. I still think a poor
plug/socket connection is a likely cause.
--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
The half inch radius destruction was total , burning down to glass mat , the
thickness of the board. I just cannot see that happening due to an arcing
contact inside the mated plug and socket and the heat conducted through an
inch or so of metal conductor , with only marginal melting to the line cord
plug.
Without carving into the line plug I cannot see the surface of the female
part but the male pins in the chassis section show no pitting or sign of
arcing.
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/