Heuristic learning

[N_Cook]

No-one ever told me to be wary if test speaker voice-coil continuity with a
DVM.
Speaker o/c in the amp cab, but after process of removing showed proper
ohmage. Exposed pigtails looked ok and tested ok, so heated up and removed
the dome. Made wire-taps to both voice-coil lead outs and tested each
pigtail in turn.
Both had the same break at about the same point of slowly manually pushing
the cone in and out, so assumed I was deflecting the cone slightly. Very
unlikely the same paint-covered failure at the joins of pigtails to wires ,
or anywhere else, so what was I doing wrong?

Answers here please

 

[hr(bob) hofmann@att.net]

On Jan 9, 12:01 pm, "N_Cook" <dive...@tcp.co.uk> wrote:

No-one ever told me to be wary if test speaker voice-coil continuity with a
DVM.
Speaker o/c in the amp cab, but after process of removing showed proper
ohmage. Exposed pigtails looked ok and tested ok, so heated up and removed
the dome. Made wire-taps to both voice-coil lead outs and tested each
pigtail in turn.
Both had the same break at about the same point of slowly manually pushing
the cone in and out, so assumed I was deflecting the cone slightly. Very
unlikely the same paint-covered failure at the joins of pigtails to wires ,
or anywhere else, so what was I doing wrong?

Answers here please

From the west side of the pond.

What is o/c in the amp cab? The break could be at the wire junctions
in the soldering process introduced some contamination/corrosive
material. You don't say how old the speaker was, but any corrosion
combined with the repetitive motion could vause a weak spot, THen if
the volume was high, there could be local heating further aiding the
process of failure.

 

[N_Cook]

N_Cook <diverse@tcp.co.uk> wrote in message
news:hiagam$e0j$1@news.eternal-september.org...

No-one ever told me to be wary if test speaker voice-coil continuity with
a
DVM.
Speaker o/c in the amp cab, but after process of removing showed proper
ohmage. Exposed pigtails looked ok and tested ok, so heated up and removed
the dome. Made wire-taps to both voice-coil lead outs and tested each
pigtail in turn.
Both had the same break at about the same point of slowly manually pushing
the cone in and out, so assumed I was deflecting the cone slightly. Very
unlikely the same paint-covered failure at the joins of pigtails to wires
,
or anywhere else, so what was I doing wrong?

Answers here please

No breaks in the internal wiring.
With using DVM and pushing the cone, generated enough voltage to fool the
continuity mode into not bleeping. Intermittant fault was actually at the
outside tag terminal inside the solder, pigtail corrosion/fatigue but held
in place and disquised by the overlaying lacquer.

 

[Ron]

On 10/01/2010 04:50, hr(bob) hofmann@att.net wrote:

On Jan 9, 12:01 pm, "N_Cook"<dive...@tcp.co.uk> wrote:
No-one ever told me to be wary if test speaker voice-coil continuity with a
DVM.
Speaker o/c in the amp cab, but after process of removing showed proper
ohmage. Exposed pigtails looked ok and tested ok, so heated up and removed
the dome. Made wire-taps to both voice-coil lead outs and tested each
pigtail in turn.
Both had the same break at about the same point of slowly manually pushing
the cone in and out, so assumed I was deflecting the cone slightly. Very
unlikely the same paint-covered failure at the joins of pigtails to wires ,
or anywhere else, so what was I doing wrong?

Answers here please

From the west side of the pond.

What is o/c in the amp cab? The break could be at the wire junctions
in the soldering process introduced some contamination/corrosive
material. You don't say how old the speaker was, but any corrosion
combined with the repetitive motion could vause a weak spot, THen if
the volume was high, there could be local heating further aiding the
process of failure.

In my experience the first fail spot due to fatigue is the braid of the
pigtail where it's soldered to the connector tag, it's difficult to
spot. Next place is on the inside of the cone where the tail of the
voice coil is soldered to the pigtail. this is presuming that the
speaker isn't being overdriven or the v/c isnt rubbing in the gap.

Ron(UK)