Poor speaker connection blowing an amp?
 

Has anyone ever come across this ?
Back emf induced by breaking the current to an inductor, in this case the
speaker coil.
Its a real effect but has it ever been known to blow an amp, as the induced
voltage would be in the coil and not the amp, I would have thought.
To demonstrate, if you're brave, connect a small 12Volt relay to a 12V
source , holding your fingers over the terminals of the relay and then break
the connection at the supply, you will get a belt of presumably 100Volts or
more. I did it accidently once, testing a relay

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

Poor speaker connection blowing an amp?
 

N Cook wrote:

Has anyone ever come across this ?
Back emf induced by breaking the current to an inductor, in this case the
speaker coil.
Its a real effect but has it ever been known to blow an amp, as the induced
voltage would be in the coil and not the amp, I would have thought.

It cant hurt the amp. At worst it could arc over the gap, but its
current delivery, not v, and the amp's very much in control, not the
LS. Think it through.


To demonstrate, if you're brave,

& really dumb


NT

Poor speaker connection blowing an amp?
 

N Cook wrote:
Has anyone ever come across this ?
Back emf induced by breaking the current to an inductor, in this case the
speaker coil.

What amp is it?

Are we talking valve amp, transformer coupled solid state amp, or normal
output stage SS amp?



Ron(UK)

Poor speaker connection blowing an amp?
 

Ron(UK) wrote in message
...
N Cook wrote:
Has anyone ever come across this ?
Back emf induced by breaking the current to an inductor, in this case
the
speaker coil.

What amp is it?

Are we talking valve amp, transformer coupled solid state amp, or normal
output stage SS amp?



Ron(UK)

I could see it as a problem with valve amps as the main "inductor" is on the
amp side of a break. I should have limited the question to solid state amps

Poor speaker connection blowing an amp?
 

N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
Has anyone ever come across this ?
Back emf induced by breaking the current to an inductor, in this case
the
speaker coil.
What amp is it?

Are we talking valve amp, transformer coupled solid state amp, or normal
output stage SS amp?



Ron(UK)

I could see it as a problem with valve amps as the main "inductor" is on the
amp side of a break. I should have limited the question to solid state amps


So, what amp is it? make & model number?

Ron(UK)

Poor speaker connection blowing an amp?
 

Ron(UK) wrote in message
...
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
Has anyone ever come across this ?
Back emf induced by breaking the current to an inductor, in this case
the
speaker coil.
What amp is it?

Are we talking valve amp, transformer coupled solid state amp, or
normal
output stage SS amp?



Ron(UK)

I could see it as a problem with valve amps as the main "inductor" is on
the
amp side of a break. I should have limited the question to solid state
amps


So, what amp is it? make & model number?

Ron(UK)

hypothetical, any amp + speaker + any sort of potential break/poor contact.
I forget the maths now but in theory (no R etc) then for an instantaneous
break can't the indiced V be near infinite for an infinitesimal time after
the break. So a few hundred volts a nS or so after a break could be induced
and easily arc across a practical, poor contact, rather than a theoretical
clean break.

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

Poor speaker connection blowing an amp?
 

"N Cook" wrote in message
...
Has anyone ever come across this ?
Back emf induced by breaking the current to an inductor, in this case the
speaker coil.
Its a real effect but has it ever been known to blow an amp, as the
induced
voltage would be in the coil and not the amp, I would have thought.
To demonstrate, if you're brave, connect a small 12Volt relay to a 12V
source , holding your fingers over the terminals of the relay and then
break
the connection at the supply, you will get a belt of presumably 100Volts
or
more. I did it accidently once, testing a relay

That's why I hate impedance selectors... wired around
the one on my Marshall. Terminal strip and jumper
wire is the only way to do it right a la old PA's.
__
Steve
..

Poor speaker connection blowing an amp?
 

On Tue, 20 Feb 2007 11:27:12 -0000, "N Cook" wrote:

Has anyone ever come across this ?
Back emf induced by breaking the current to an inductor, in this case the
speaker coil.
Its a real effect but has it ever been known to blow an amp, as the induced
voltage would be in the coil and not the amp, I would have thought.
To demonstrate, if you're brave, connect a small 12Volt relay to a 12V
source , holding your fingers over the terminals of the relay and then break
the connection at the supply, you will get a belt of presumably 100Volts or
more. I did it accidently once, testing a relay

We've seen it in all kinds of gears. The more extreme cases are in dance club
sound systems. I've seen Crown power amps with big craters in the cases of
stainless steel TO-3 case transistors. When one of those subwoofers lets go
there's a lot of energy looking for somewhere to go....

Ron

Poor speaker connection blowing an amp?
 

N Cook wrote:

Has anyone ever come across this ?
Back emf induced by breaking the current to an inductor, in this case the
speaker coil.
Its a real effect but has it ever been known to blow an amp, as the induced
voltage would be in the coil and not the amp, I would have thought.
To demonstrate, if you're brave, connect a small 12Volt relay to a 12V
source , holding your fingers over the terminals of the relay and then break
the connection at the supply, you will get a belt of presumably 100Volts or
more. I did it accidently once, testing a relay

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





If it's a tube amp, you could get flyback voltages causing arcing at
tube sockets, perhaps punched through insulation in the output
transformer...

Poor speaker connection blowing an amp?
 

On Tue, 20 Feb 2007 11:27:31 -0500 RonSonic
wrote in Message id: :

I've seen Crown power amps with big craters in the cases of
stainless steel TO-3 case transistors.

!

In 25 years in the repair industry, I've yet to see a failure where a TO-3
ends it's life that violently.

Got any pics? :)

Poor speaker connection blowing an amp?
 

JW wrote in
:

On Tue, 20 Feb 2007 11:27:31 -0500 RonSonic
wrote in Message id: :

I've seen Crown power amps with big craters in the cases of
stainless steel TO-3 case transistors.

!

In 25 years in the repair industry, I've yet to see a failure where a
TO-3 ends it's life that violently.

Got any pics? :)

Agreed. Everything else around it will melt and burn to a crisp
before the TO-3 even discolours. On the other hand, the plastic
package TO-3P (looks like an oversized TO-220) will flames
out in a kaleidoscope of colours.

--
If it's not broken, fix it till it is.

Poor speaker connection blowing an amp?
 

"N Cook" wrote in
:

Has anyone ever come across this ?
Back emf induced by breaking the current to an inductor, in this case
the speaker coil.
Its a real effect but has it ever been known to blow an amp, as the
induced voltage would be in the coil and not the amp, I would have
thought. To demonstrate, if you're brave, connect a small 12Volt relay
to a 12V source , holding your fingers over the terminals of the relay
and then break the connection at the supply, you will get a belt of
presumably 100Volts or more. I did it accidently once, testing a
relay

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





SS amps of the power MOSFET variety are suceptible to fail
under those conditions. This is due to the low (20-30volt)
gate-to-source breakdown.

--
If it's not broken, fix it till it is.

Poor speaker connection blowing an amp?
 

On Wed, 21 Feb 2007 21:50:39 GMT, Doggone wrote:

JW wrote in
:

On Tue, 20 Feb 2007 11:27:31 -0500 RonSonic
wrote in Message id: :

I've seen Crown power amps with big craters in the cases of
stainless steel TO-3 case transistors.

!

In 25 years in the repair industry, I've yet to see a failure where a
TO-3 ends it's life that violently.

Got any pics? :)

Agreed. Everything else around it will melt and burn to a crisp
before the TO-3 even discolours.

Depends on how fast it goes, doesn't it. No, I don't have pic's but there's sure
to be some out there. It really isn't that rare.

Ron



Ron

Sweet Blues pedal demo up at http://www.myspace.com/ronsonicpedal...musicalgadgets

Poor speaker connection blowing an amp?
 

RonSonic wrote:
On Wed, 21 Feb 2007 21:50:39 GMT, Doggone wrote:

JW wrote in
:

On Tue, 20 Feb 2007 11:27:31 -0500 RonSonic
wrote in Message id: :

I've seen Crown power amps with big craters in the cases of
stainless steel TO-3 case transistors.
!

In 25 years in the repair industry, I've yet to see a failure where a
TO-3 ends it's life that violently.

Got any pics? :)
Agreed. Everything else around it will melt and burn to a crisp
before the TO-3 even discolours.

Depends on how fast it goes, doesn't it. No, I don't have pic's but there's sure
to be some out there. It really isn't that rare.

Ron

I`ve seen plenty of those big old Peavey poweramps with the T03s melted
right through the can.


Ron(UK)