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I Built and Used My First Incandescent Bulb Current-Limiter



 
 
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  #1  
Old December 21st 20, 12:44 AM posted to rec.audio.pro
Paul Dorman
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Posts: 51
Default I Built and Used My First Incandescent Bulb Current-Limiter

This was used for a guitar amp that was continually
blowing slow-blow fuses instantly upon turning the amp
on.

https://www.youtube.com/watch?v=k5oNQ1etN2c

In my case, the bulb would briefly light up, and then
fade out within about a second. I read this meant the
amp was normal, and didn't have a short to ground, and
when I plugged the amp into the wall normally, I was able
to trouble-shoot it normally.

But I would assume the bulb lighting up initially, is due
to the initial in-rush current, that charges up the electrolytic
filtering caps, on the outputs of the rectifiers?

Because the initial 1 second flash only happened with a
linear power supply guitar amp, and did not happen with
my switched-mode guitar amp. With the latter, the bulb
never glowed noticeably, even at turn-on.
Ads
  #2  
Old December 21st 20, 04:01 AM posted to rec.audio.pro
[email protected]
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Posts: 36
Default I Built and Used My First Incandescent Bulb Current-Limiter

Paul wrote:
============
>
> But I would assume the bulb lighting up initially, is due
> to the initial in-rush current, that charges up the electrolytic
> filtering caps, on the outputs of the rectifiers?
>


** The largest part of the " inrush surge " is down to the iron transformer core *magnetising* and losing nearly all of its inductance at switch own.
Can take 20 cycles of AC power for the core to unmagnetise too.

SMPSs usually surge hard at a switch on too, yours must be an exception.


...... Phil
  #3  
Old December 21st 20, 11:39 AM posted to rec.audio.pro
Don Pearce[_3_]
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Posts: 2,350
Default I Built and Used My First Incandescent Bulb Current-Limiter

On Sun, 20 Dec 2020 16:44:56 -0700, Paul Dorman >
wrote:

>This was used for a guitar amp that was continually
>blowing slow-blow fuses instantly upon turning the amp
>on.
>
> https://www.youtube.com/watch?v=k5oNQ1etN2c
>
>In my case, the bulb would briefly light up, and then
>fade out within about a second. I read this meant the
>amp was normal, and didn't have a short to ground, and
>when I plugged the amp into the wall normally, I was able
>to trouble-shoot it normally.
>
>But I would assume the bulb lighting up initially, is due
>to the initial in-rush current, that charges up the electrolytic
>filtering caps, on the outputs of the rectifiers?
>
>Because the initial 1 second flash only happened with a
>linear power supply guitar amp, and did not happen with
>my switched-mode guitar amp. With the latter, the bulb
>never glowed noticeably, even at turn-on.


You will find that the bulb has a rather finite lifetime.Instead use
the part designed for the job, a negative temperature coefficient
(NTC) thermistor. Any switched mode power supply is most likely to
already have one fitted, which is why your bulb seems to do nothing.

d
  #4  
Old December 21st 20, 12:06 PM posted to rec.audio.pro
[email protected]
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Posts: 36
Default I Built and Used My First Incandescent Bulb Current-Limiter

Don Pearce Pomy Bull**** Artist puked:

===================================
>
>
> >Because the initial 1 second flash only happened with a
> >linear power supply guitar amp, and did not happen with
> >my switched-mode guitar amp. With the latter, the bulb
> >never glowed noticeably, even at turn-on.


------------------------------------------------------------------------------
> You will find that the bulb has a rather finite lifetime.
>


** ROTFLMAO - how ****ing ABSURD !!


> Instead use the part designed for the job,


** How do you spell * misconstrue *" ????

The Don Pearce retard needs to know so he can look it up.....


> a negative temperature coefficient
> (NTC) thermistor. Any switched mode power supply is most likely to
> already have one fitted, which is why your bulb seems to do nothing.
>

** Wot utter GARBAGE !!!!

Don the Nong has less that ZERO idea of what he is speaking about.


....... Phil



  #5  
Old December 21st 20, 12:21 PM posted to rec.audio.pro
Don Pearce[_3_]
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Posts: 2,350
Default I Built and Used My First Incandescent Bulb Current-Limiter

On Mon, 21 Dec 2020 03:06:38 -0800 (PST), "
> wrote:

> Don Pearce Pomy Bull**** Artist puked:
>
>===================================
>>
>>
>> >Because the initial 1 second flash only happened with a
>> >linear power supply guitar amp, and did not happen with
>> >my switched-mode guitar amp. With the latter, the bulb
>> >never glowed noticeably, even at turn-on.

>
>------------------------------------------------------------------------------
>> You will find that the bulb has a rather finite lifetime.
>>

>
>** ROTFLMAO - how ****ing ABSURD !!
>
>
>> Instead use the part designed for the job,

>
> ** How do you spell * misconstrue *" ????
>
>The Don Pearce retard needs to know so he can look it up.....
>
>
>> a negative temperature coefficient
>> (NTC) thermistor. Any switched mode power supply is most likely to
>> already have one fitted, which is why your bulb seems to do nothing.
>>

>** Wot utter GARBAGE !!!!
>
>Don the Nong has less that ZERO idea of what he is speaking about.
>
>
>...... Phil
>
>

You are insulting a man who has designed switched mode power supplies,
and has included NTC thermistors for the purpose of limiting switch-on
inrush current. These thermistors are normally specified by customers
who have inrush current as part of their specification.

Have a read of an application note from TDK.

https://product.tdk.com/info/en/prod...c-limiter.html

d

  #6  
Old December 21st 20, 12:52 PM posted to rec.audio.pro
Don Pearce[_3_]
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Posts: 2,350
Default I Built and Used My First Incandescent Bulb Current-Limiter

On Mon, 21 Dec 2020 11:21:26 GMT, (Don Pearce) wrote:

>On Mon, 21 Dec 2020 03:06:38 -0800 (PST), "
> wrote:
>
>> Don Pearce Pomy Bull**** Artist puked:
>>
>>===================================
>>>
>>>
>>> >Because the initial 1 second flash only happened with a
>>> >linear power supply guitar amp, and did not happen with
>>> >my switched-mode guitar amp. With the latter, the bulb
>>> >never glowed noticeably, even at turn-on.

>>
>>------------------------------------------------------------------------------
>>> You will find that the bulb has a rather finite lifetime.
>>>

>>
>>** ROTFLMAO - how ****ing ABSURD !!
>>
>>
>>> Instead use the part designed for the job,

>>
>> ** How do you spell * misconstrue *" ????
>>
>>The Don Pearce retard needs to know so he can look it up.....
>>
>>
>>> a negative temperature coefficient
>>> (NTC) thermistor. Any switched mode power supply is most likely to
>>> already have one fitted, which is why your bulb seems to do nothing.
>>>

>>** Wot utter GARBAGE !!!!
>>
>>Don the Nong has less that ZERO idea of what he is speaking about.
>>
>>
>>...... Phil
>>
>>

>You are insulting a man who has designed switched mode power supplies,
>and has included NTC thermistors for the purpose of limiting switch-on
>inrush current. These thermistors are normally specified by customers
>who have inrush current as part of their specification.
>
>Have a read of an application note from TDK.
>
>
https://product.tdk.com/info/en/prod...c-limiter.html
>
>d


Or if you aren't into reading, try this

https://www.youtube.com/watch?v=U_0trB4ObwE

d
  #7  
Old December 21st 20, 12:55 PM posted to rec.audio.pro
[email protected]
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Posts: 36
Default I Built and Used My First Incandescent Bulb Current-Limiter

Don Pearce, Lying, Bull****ting pommy idiot spewed:

===========================================

> >> >Because the initial 1 second flash only happened with a
> >> >linear power supply guitar amp, and did not happen with
> >> >my switched-mode guitar amp. With the latter, the bulb
> >> >never glowed noticeably, even at turn-on.

> >
> >------------------------------------------------------------------------------
> >> You will find that the bulb has a rather finite lifetime.
> >>

> >
> >** ROTFLMAO - how ****ing ABSURD !!
> >


** Suspect Don has realised his stupid blunder here.
Bit will never admit to it.
--------------------------------------------------------------------


> >> a negative temperature coefficient
> >> (NTC) thermistor. Any switched mode power supply is most likely to
> >> already have one fitted, which is why your bulb seems to do nothing.
> >>

> >** Wot utter GARBAGE !!!!
> >
> >Don the Nong has less that ZERO idea of what he is speaking about.
> >

-----------------------------------------------------------------------
>
> >

> You are insulting a man who has designed switched mode power supplies,


** But clearly, not insulted him near enough to shut the idiot up.


> and has included NTC thermistors for the purpose of limiting switch-on
> inrush current.


** The geriatric fool has no clue at all.



...... Phil

  #8  
Old December 21st 20, 01:04 PM posted to rec.audio.pro
Don Pearce[_3_]
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Posts: 2,350
Default I Built and Used My First Incandescent Bulb Current-Limiter

On Mon, 21 Dec 2020 10:39:57 GMT, (Don Pearce) wrote:

>On Sun, 20 Dec 2020 16:44:56 -0700, Paul Dorman >
>wrote:
>
>>This was used for a guitar amp that was continually
>>blowing slow-blow fuses instantly upon turning the amp
>>on.
>>
>>
https://www.youtube.com/watch?v=k5oNQ1etN2c
>>
>>In my case, the bulb would briefly light up, and then
>>fade out within about a second. I read this meant the
>>amp was normal, and didn't have a short to ground, and
>>when I plugged the amp into the wall normally, I was able
>>to trouble-shoot it normally.
>>
>>But I would assume the bulb lighting up initially, is due
>>to the initial in-rush current, that charges up the electrolytic
>>filtering caps, on the outputs of the rectifiers?
>>
>>Because the initial 1 second flash only happened with a
>>linear power supply guitar amp, and did not happen with
>>my switched-mode guitar amp. With the latter, the bulb
>>never glowed noticeably, even at turn-on.

>
>You will find that the bulb has a rather finite lifetime.Instead use
>the part designed for the job, a negative temperature coefficient
>(NTC) thermistor. Any switched mode power supply is most likely to
>already have one fitted, which is why your bulb seems to do nothing.
>
>d


I should add. The cold/hot resistance change is much greater in the
NTC thermistor, which means that while it does a much better job of
limiting the initial inrush current, its resistance once it reaches
its final state will be only a few tens of milliohms, so it becomes
essentially invisible to the circuit in operation.

This would be a typical choice

https://uk.farnell.com/ametherm/sl22...tor/dp/1703898

d
  #9  
Old December 21st 20, 09:32 PM posted to rec.audio.pro
Scott Dorsey
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Posts: 16,798
Default I Built and Used My First Incandescent Bulb Current-Limiter

In article >,
Paul Dorman > wrote:
>This was used for a guitar amp that was continually
>blowing slow-blow fuses instantly upon turning the amp
>on.
>
> https://www.youtube.com/watch?v=k5oNQ1etN2c
>
>In my case, the bulb would briefly light up, and then
>fade out within about a second. I read this meant the
>amp was normal, and didn't have a short to ground, and
>when I plugged the amp into the wall normally, I was able
>to trouble-shoot it normally.
>
>But I would assume the bulb lighting up initially, is due
>to the initial in-rush current, that charges up the electrolytic
>filtering caps, on the outputs of the rectifiers?


No. This is a "power-on thump" which is caused by the coupling capacitors
charging up, not the power supply.

It's made much worse with amplifiers that run on a single supply rail, so
the output of the power amp stage is sitting halfway between the supply
rail and ground during normal operation. This means there is a huge
coupling capacitor from the output stage to the speaker and that has to
charge up. While it is charging up, the woofer coil will bottom out.

Well-designed amplifiers have a protection relay that cuts the speaker off
when there is any appreciable DC offset. It will sometimes take a little
time to stabilize because of the turn-on thump.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #10  
Old December 21st 20, 10:30 PM posted to rec.audio.pro
[email protected]
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Posts: 36
Default I Built and Used My First Incandescent Bulb Current-Limiter

Scott Dorsey wrote:

===================
> >
> >But I would assume the bulb lighting up initially, is due
> >to the initial in-rush current, that charges up the electrolytic
> >filtering caps, on the outputs of the rectifiers?

>
> No. This is a "power-on thump" which is caused by the coupling capacitors
> charging up, not the power supply.
>


** The OP never mentioned any " thump" and is not talking about one.

> It's made much worse with amplifiers that run on a single supply rail, so
> the output of the power amp stage is sitting halfway between the supply
> rail and ground during normal operation. This means there is a huge
> coupling capacitor from the output stage to the speaker and that has to
> charge up. While it is charging up, the woofer coil will bottom out.
>
>

** Nonsense, speaker output electros ( rarely seen in the last 30 years) do not do that, they charge slowly.

I = C.dv/dt

if C = 2000uF and the cap charges to 30V in 0.5 second, I = 120mA.

To " bottom out " a woofer a takes several amps.

> Well-designed amplifiers have a protection relay that cuts the speaker off
> when there is any appreciable DC offset. It will sometimes take a little
> time to stabilize because of the turn-on thump.


** Direct coupled amps sometimes have such relays, a great many do not and don't need them.

In most cases, a simple muting FET between the pre and power stage does the job.


.......... Phil

 




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