Resistor in DC supply line...

[ehsjr]

On 8/13/2023 12:58 PM, Cursitor Doom wrote:

On Sun, 13 Aug 2023 12:51:09 -0400, legg <legg@nospam.magma.ca> wrote:

Cheaper than a fuse.

Yeah, but ONE OHM? How much current is that going to limit?

Phil nailed it. At power on, the 2200 uf is a dead short circuit
to DC. At that instant it will draw (or try to draw) infinite
current from the 13.8 V supply. Of course the supply has internal
resistance, and connectors and circuit traces/wiring adds more,
but you still get a huge draw. Exactly as Phil said, that resistor
limits the peak current. As the 2200uf charges, the current draw
reduces and limiting peak current in that circuit is no longer
important - until the next time the transceiver it powered off
long enough for the 2200uf to fully discharge. After that, at the
next power on, the resistor once again is important as a peak
limiter.

That peak limiting action stresses the resistor every time the
radio is turned on (unless it was turned off for only a brief
time). Over the course of ~35 years it is not remarkable that
it failed. That is exactly what Phil indicated. And he also
mentioned the fact that it (in conjunction with the caps) provides
a measure of noise filtering.

The thread may be a source of confusion. It may be best if you
re-read, and stick with, Phil\'s reply.

Ed

 

[boB]

On Sun, 13 Aug 2023 09:30:28 +0100, Cursitor Doom <cd@notformail.com>
wrote:

The aforementioned resistor failed open-circuit without any external
sign of overheating at all. Bonus points will be awarded for anyone
who can think of a reason why this might have occurred.

Filtering for the amp from engine noise. It says 13.8V so assuming a
vehicle powering it.

The resistor probably blew from inrush power too many times to charge
that 2200uF cap.

boB

 

[Phil Hobbs]

ehsjr <ehsjr@verizon.net> wrote:

On 8/13/2023 12:58 PM, Cursitor Doom wrote:
On Sun, 13 Aug 2023 12:51:09 -0400, legg <legg@nospam.magma.ca> wrote:

Cheaper than a fuse.

Yeah, but ONE OHM? How much current is that going to limit?

Phil nailed it. At power on, the 2200 uf is a dead short circuit
to DC. At that instant it will draw (or try to draw) infinite
current from the 13.8 V supply. Of course the supply has internal
resistance, and connectors and circuit traces/wiring adds more,
but you still get a huge draw. Exactly as Phil said, that resistor
limits the peak current. As the 2200uf charges, the current draw
reduces and limiting peak current in that circuit is no longer
important - until the next time the transceiver it powered off
long enough for the 2200uf to fully discharge. After that, at the
next power on, the resistor once again is important as a peak
limiter.

That peak limiting action stresses the resistor every time the
radio is turned on (unless it was turned off for only a brief
time). Over the course of ~35 years it is not remarkable that
it failed. That is exactly what Phil indicated. And he also
mentioned the fact that it (in conjunction with the caps) provides
a measure of noise filtering.

The thread may be a source of confusion. It may be best if you
re-read, and stick with, Phil\'s reply.

Ed

If the 1 ohm is the main inrush limiter, it’ll absorb the same amount of
energy as it would in the case of an input short, i. e. 1/2 CV**2.

That’s 14V **2 * .0022F ~= 0.4 J, which is a lot for a film resistor of
that size—like 100x the usual rating.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics,
Electro-optics, Photonics, Analog Electronics

 

[legg]

On Sun, 13 Aug 2023 22:31:28 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

ehsjr <ehsjr@verizon.net> wrote:
On 8/13/2023 12:58 PM, Cursitor Doom wrote:
On Sun, 13 Aug 2023 12:51:09 -0400, legg <legg@nospam.magma.ca> wrote:

Cheaper than a fuse.

Yeah, but ONE OHM? How much current is that going to limit?

Phil nailed it. At power on, the 2200 uf is a dead short circuit
to DC. At that instant it will draw (or try to draw) infinite
current from the 13.8 V supply. Of course the supply has internal
resistance, and connectors and circuit traces/wiring adds more,
but you still get a huge draw. Exactly as Phil said, that resistor
limits the peak current. As the 2200uf charges, the current draw
reduces and limiting peak current in that circuit is no longer
important - until the next time the transceiver it powered off
long enough for the 2200uf to fully discharge. After that, at the
next power on, the resistor once again is important as a peak
limiter.

That peak limiting action stresses the resistor every time the
radio is turned on (unless it was turned off for only a brief
time). Over the course of ~35 years it is not remarkable that
it failed. That is exactly what Phil indicated. And he also
mentioned the fact that it (in conjunction with the caps) provides
a measure of noise filtering.

The thread may be a source of confusion. It may be best if you
re-read, and stick with, Phil\'s reply.

Ed


If the 1 ohm is the main inrush limiter, it’ll absorb the same amount of
energy as it would in the case of an input short, i. e. 1/2 CV**2.

That’s 14V **2 * .0022F ~= 0.4 J, which is a lot for a film resistor of
that size—like 100x the usual rating.

Cheers

Phil Hobbs

It\'s a 4W amp. I expect that 1R is only a fraction of the source
impedance, and that the cap ESR is also a good fraction of that
1R figure.

Anyways, until a complete repair is achieved, the single point
fault is all just speculation.

RL

 

[Cursitor Doom]

On Sun, 13 Aug 2023 15:12:18 -0700, boB <boB@K7IQ.com> wrote:

On Sun, 13 Aug 2023 09:30:28 +0100, Cursitor Doom <cd@notformail.com
wrote:

The aforementioned resistor failed open-circuit without any external
sign of overheating at all. Bonus points will be awarded for anyone
who can think of a reason why this might have occurred.


Filtering for the amp from engine noise. It says 13.8V so assuming a
vehicle powering it.

The resistor probably blew from inrush power too many times to charge
that 2200uF cap.

Excellent point. I overlooked how big that cap and how it must \'be
seen\' by the in-rush current at switch-on until you mentioned that.
Many thanks.

 

[Ricky]

On Sunday, August 13, 2023 at 5:31:18 PM UTC-4, Eddy Lee wrote:

On Sunday, August 13, 2023 at 2:16:12 PM UTC-7, Ricky wrote:
On Sunday, August 13, 2023 at 4:51:43 PM UTC-4, Eddy Lee wrote:
On Sunday, August 13, 2023 at 12:54:54 PM UTC-7, John Larkin wrote:
On Sun, 13 Aug 2023 10:14:04 -0700 (PDT), Eddy Lee
eddy7...@gmail.com> wrote:
On Sunday, August 13, 2023 at 9:58:43?AM UTC-7, Cursitor Doom wrote:
On Sun, 13 Aug 2023 12:51:09 -0400, legg <le...@nospam.magma.ca> wrote:

Cheaper than a fuse.

Yeah, but ONE OHM? How much current is that going to limit?

Resistors can sometimes handle 10x rated current or power briefly. It can give out smoke signals and/or change requests (burnt out mark).

I also use halogen/incandescent light bulbs as current meters and fuses.
Check out Diodes\' AP22652 current limiter chip. Very slick.

We tried a TI E-fuse thing and it worked like a real fuse, just once,
except that it failed shorted.
Then it\'s not a fuse.
A wire bond might be a good fuse. Imagine an IC that had a couple of
input pins and a bunch of outputs and just wire bonds inside.
Sometimes i use very thin wire as fuse.
Why does that not surprise me at all?
A fuse is just a thin wire in a safe place. As long as I know the wire is safe from burning other thing, it\'s as good as a fuse.

And you continue to prove me right!

--

Rick C.

+- Get 1,000 miles of free Supercharging
+- Tesla referral code - https://ts.la/richard11209

 

[Phil Hobbs]

legg <legg@nospam.magma.ca> wrote:

On Sun, 13 Aug 2023 22:31:28 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

ehsjr <ehsjr@verizon.net> wrote:
On 8/13/2023 12:58 PM, Cursitor Doom wrote:
On Sun, 13 Aug 2023 12:51:09 -0400, legg <legg@nospam.magma.ca> wrote:

Cheaper than a fuse.

Yeah, but ONE OHM? How much current is that going to limit?

Phil nailed it. At power on, the 2200 uf is a dead short circuit
to DC. At that instant it will draw (or try to draw) infinite
current from the 13.8 V supply. Of course the supply has internal
resistance, and connectors and circuit traces/wiring adds more,
but you still get a huge draw. Exactly as Phil said, that resistor
limits the peak current. As the 2200uf charges, the current draw
reduces and limiting peak current in that circuit is no longer
important - until the next time the transceiver it powered off
long enough for the 2200uf to fully discharge. After that, at the
next power on, the resistor once again is important as a peak
limiter.

That peak limiting action stresses the resistor every time the
radio is turned on (unless it was turned off for only a brief
time). Over the course of ~35 years it is not remarkable that
it failed. That is exactly what Phil indicated. And he also
mentioned the fact that it (in conjunction with the caps) provides
a measure of noise filtering.

The thread may be a source of confusion. It may be best if you
re-read, and stick with, Phil\'s reply.

Ed


If the 1 ohm is the main inrush limiter, it’ll absorb the same amount of
energy as it would in the case of an input short, i. e. 1/2 CV**2.

That’s 14V **2 * .0022F ~= 0.4 J, which is a lot for a film resistor of
that size—like 100x the usual rating.

Cheers

Phil Hobbs

It\'s a 4W amp. I expect that 1R is only a fraction of the source
impedance, and that the cap ESR is also a good fraction of that
1R figure.

Which is the point exactly. The 1 ohm 1/4 watt film resistor doesn’t do
anything much about inrush, because it can’t.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

 

[Jan Panteltje]

On a sunny day (Sun, 13 Aug 2023 12:46:46 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<lhcidi1cigt60otahgttji3h4nq9dajano@4ax.com>:

On Sun, 13 Aug 2023 17:47:47 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 13 Aug 2023 06:56:43 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 13 Aug 2023 09:26:15 +0100, Cursitor Doom <cd@notformail.com
wrote:

Gentlemen,

I refer you to this circuit fragment:

https://disk.yandex.com/i/O-4WvVAgNjmNlg

What\'s R30 supposed to achieve? This is right at the top of the
schematic, btw.

It\'s audio. Circuit randomness is high.

But you say essentially the same thing about RF! Am I to assume you\'re
only comfortable answering topics relating to the bit of the spectrum
in between? :-D

RF generally has measurable things: power, noise figure, impedances.
Audio tends to be more arbitrary, as in \"I like how that sounds.\"

I think sine waves are boring, at both ends of the spectrum.

Cannot any wave form be seen as the sum of sine waves?
Audio is quite a challenge in some cases.
Good signal to noise, low distortion, very high power amps,
synthesizers, special effects...microphones, companders, expanders... no end to it all
speakers: electrostatic piezo, dynamic ...
Facinating field!
Same for RF.

 

[John Larkin]

On Mon, 14 Aug 2023 02:16:29 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Sun, 13 Aug 2023 12:46:46 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
lhcidi1cigt60otahgttji3h4nq9dajano@4ax.com>:

On Sun, 13 Aug 2023 17:47:47 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 13 Aug 2023 06:56:43 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 13 Aug 2023 09:26:15 +0100, Cursitor Doom <cd@notformail.com
wrote:

Gentlemen,

I refer you to this circuit fragment:

https://disk.yandex.com/i/O-4WvVAgNjmNlg

What\'s R30 supposed to achieve? This is right at the top of the
schematic, btw.

It\'s audio. Circuit randomness is high.

But you say essentially the same thing about RF! Am I to assume you\'re
only comfortable answering topics relating to the bit of the spectrum
in between? :-D

RF generally has measurable things: power, noise figure, impedances.
Audio tends to be more arbitrary, as in \"I like how that sounds.\"

I think sine waves are boring, at both ends of the spectrum.

Cannot any wave form be seen as the sum of sine waves?
Audio is quite a challenge in some cases.
Good signal to noise, low distortion, very high power amps,
synthesizers, special effects...microphones, companders, expanders... no end to it all
speakers: electrostatic piezo, dynamic ...
Facinating field!
Same for RF.

At 12 GHz, you can resonate out the capacitances and trace lengths and
such. At DC-to-12 GHz, you can\'t.

 

[Jan Panteltje]

On a sunny day (Sun, 13 Aug 2023 20:23:16 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<qd7jdidrg36rdcn2k3e2pdt905odhr96sq@4ax.com>:

On Mon, 14 Aug 2023 02:16:29 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Sun, 13 Aug 2023 12:46:46 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
lhcidi1cigt60otahgttji3h4nq9dajano@4ax.com>:

On Sun, 13 Aug 2023 17:47:47 +0100, Cursitor Doom <cd@notformail.com
wrote:

On Sun, 13 Aug 2023 06:56:43 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sun, 13 Aug 2023 09:26:15 +0100, Cursitor Doom <cd@notformail.com
wrote:

Gentlemen,

I refer you to this circuit fragment:

https://disk.yandex.com/i/O-4WvVAgNjmNlg

What\'s R30 supposed to achieve? This is right at the top of the
schematic, btw.

It\'s audio. Circuit randomness is high.

But you say essentially the same thing about RF! Am I to assume you\'re
only comfortable answering topics relating to the bit of the spectrum
in between? :-D

RF generally has measurable things: power, noise figure, impedances.
Audio tends to be more arbitrary, as in \"I like how that sounds.\"

I think sine waves are boring, at both ends of the spectrum.

Cannot any wave form be seen as the sum of sine waves?
Audio is quite a challenge in some cases.
Good signal to noise, low distortion, very high power amps,
synthesizers, special effects...microphones, companders, expanders... no end to it all
speakers: electrostatic piezo, dynamic ...
Facinating field!
Same for RF.

At 12 GHz, you can resonate out the capacitances and trace lengths and
such. At DC-to-12 GHz, you can\'t.

At 12 GHz to 24 GHz you cannot either!
Bandwidth

 

[boB]

On Mon, 14 Aug 2023 00:56:17 +0100, Cursitor Doom <cd@notformail.com>
wrote:

On Sun, 13 Aug 2023 15:12:18 -0700, boB <boB@K7IQ.com> wrote:

On Sun, 13 Aug 2023 09:30:28 +0100, Cursitor Doom <cd@notformail.com
wrote:

The aforementioned resistor failed open-circuit without any external
sign of overheating at all. Bonus points will be awarded for anyone
who can think of a reason why this might have occurred.


Filtering for the amp from engine noise. It says 13.8V so assuming a
vehicle powering it.

The resistor probably blew from inrush power too many times to charge
that 2200uF cap.

Excellent point. I overlooked how big that cap and how it must \'be
seen\' by the in-rush current at switch-on until you mentioned that.
Many thanks.

I did a quick LTspice simulation of this and for that first
millisecond, the 1 Ohm resistor dissipates and average of about 75
watts which is certainly possible for a 1/4 watt SMT resistor but
probably right on the edge of specifications for a pulse rated part at
1 ms

It is very possible this is why it opened up if it did that a lot and
was maybe already hot.

boB

 

[Phil Allison]

Jan Panteltje wrote:
---------------------------------

John Larkin

RF generally has measurable things: power, noise figure, impedances.
Audio tends to be more arbitrary, as in \"I like how that sounds.\"

I think sine waves are boring, at both ends of the spectrum.

Cannot any wave form be seen as the sum of sine waves?
Audio is quite a challenge in some cases.
Good signal to noise, low distortion, very high power amps,
synthesizers, special effects...microphones, companders, expanders... no end to it all
speakers: electrostatic piezo, dynamic ...
Facinating field!
Same for RF.

** The world of \"audio\" includes RF electronics used to convey audio signals - this includes all types of domestic AM and FM broadcast receivers plus wireless microphone equipment operating on the VHF or UHF bands used by entertainers.


....... Phil

 

[Anthony William Sloman]

On Monday, August 14, 2023 at 2:40:35 AM UTC+10, Cursitor Doom wrote:

On Sun, 13 Aug 2023 06:21:19 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:
On Sunday, August 13, 2023 at 4:30:36?AM UTC-4, Cursitor Doom wrote:
The aforementioned resistor failed open-circuit without any external
sign of overheating at all. Bonus points will be awarded for anyone
who can think of a reason why this might have occurred.

I\'ve used metal oxide resistors to shut down a circuit under fault conditions. That technology can be subjected to a couple hundred X it\'s max power rating and open up without a hint of visible damage. Not so with carbon film, that technology swells, smokes, chars and ultimately goes off like a fireworks sparkler.

Okay, thanks. I know the photo could have been better, but it\'s good
enough for this question: is this a MO resistor or a carbon one? The
radio it comes from is about 35 years old and with my eyesight I
struggle to tell the difference.

All you can see is the paint job on the top. If you could strip off the paint, you could get information that could give you a clue. Carbon film is black. metal film is shiny, and metal oxide tends to have coarser spiral cut than either.

--
Bill Sloman, Sydney

 

[Dan Green]

On Sun, 13 Aug 2023 17:44:49 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/13/2023 12:58 PM, Cursitor Doom wrote:
On Sun, 13 Aug 2023 12:51:09 -0400, legg <legg@nospam.magma.ca> wrote:

Cheaper than a fuse.

Yeah, but ONE OHM? How much current is that going to limit?

Phil nailed it.

Which Phil? THere are 2 on this thread and they each say totally
differnt things. Phil A says the resistor *does* limiit inrush current
and Phil H says it does essentially *nothing* to limit inrush. I know
who *my* money\'s on (hint: not the guy who thinks RF and audio are the
same thing) .

 

[Phil Allison]

Anthony William Sloman wrote:
Phil Allison wrote:
Cursitor Doom wrote:

--------------------------------------

Gentlemen,

I refer you to this circuit fragment:

https://disk.yandex.com/i/O-4WvVAgNjmNlg

What\'s R30 supposed to achieve? This is right at the top of the
schematic, btw.

** It provides peak current limiting at the moment the unit is connected to a DC supply - plus a measure of noise filtering thereafter in conjunction with the 2200uF electro.
Should be a composition or WW type, not carbon film, to survive the energy in such surges.
Nothing strange about the original film resistor failing open and invisibly when subjected to 13A spikes lasting a few milliseconds.

I\'ll second that. British power plugs have a built-in fuse and R30 makes it less likely that this fuse would blow on switch-on.

** Huh ?????

Attempted humour ?

....... Phil

 

[Jan Panteltje]

On a sunny day (Mon, 14 Aug 2023 09:35:06 +0100) it happened Dan Green
<dhg99908@hotmail.se> wrote in <6ipjditic74dd5n4h0839inqfcoaklo3v3@4ax.com>:

On Sun, 13 Aug 2023 17:44:49 -0400, ehsjr <ehsjr@verizon.net> wrote:

On 8/13/2023 12:58 PM, Cursitor Doom wrote:
On Sun, 13 Aug 2023 12:51:09 -0400, legg <legg@nospam.magma.ca> wrote:

Cheaper than a fuse.

Yeah, but ONE OHM? How much current is that going to limit?

Phil nailed it.

Which Phil? THere are 2 on this thread and they each say totally
differnt things. Phil A says the resistor *does* limiit inrush current
and Phil H says it does essentially *nothing* to limit inrush. I know
who *my* money\'s on (hint: not the guy who thinks RF and audio are the
same thing) .

If RF and audio are the same, in defense of Phil A: they are closely interwoven in commie-nukation even communication


Bats for example use frequencies that, according to wikipedia
\"Bats emit calls from about 12 kHz to 160 kHz, but the upper frequencies in this range are rapidly absorbed in air.
Many bat detectors are limited to around 15 kHz to 125 kHz at best.
Bat detectors are available commercially and also can be self-built.\"
https://en.m.wikipedia.org/wiki/Bat_detector
so the circuits processing those signals are in fact the same as RF (radio frequency) circuits.
There are stations around 120 kHz longwave. DCF 77 is at 77.5 kHz...
RF and audio circuits are deeply inter-woven,
Wireless microphones are all over the place
AM, FM modulation, radio, communication, all sort of signal processing (I already mentioned companders),
filters, many specific ways to modulate audio signals, SSB, DSB, digital...

So it is hard to draw a border line around what \'audio\' is.
If all you ever worked with is a LF audio amp..

I have build some nice ultrasonic systems too, 44 kHz
https://panteltje.nl/pub/listening_to_ultrasonics_IMG_5145.JPG

and all the small 44 kHz or so radar / distance / wind speed measurement systems I designed.
\'sound\' waves or \'audio\' is only the start, transmitting those is next.
All is interwoven, maybe apart from pick-a-second pulses for nuculear fussion ;-)

One uses the air, the other EM waves, circuits are the same, so do the laws of fishsicks.
Apart from Albert E, but Jeroen knows that.

I remember my first FM transmitter, it was a dynamic microphone element in series with the 9 V battery supply to a single
Ge transistor oscillator causing Vce changes that caused Cce changes that caused frequency changes so much you could hear a clock tick over the radio.
So all electrickety after the sound was transferred to motion by the voice coil moving in a magnet...
Audio over radio is cool.

 

[Cursitor Doom]

On Mon, 14 Aug 2023 03:13:06 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

Anthony William Sloman wrote:
Phil Allison wrote:
Cursitor Doom wrote:

--------------------------------------
Gentlemen,

I refer you to this circuit fragment:

https://disk.yandex.com/i/O-4WvVAgNjmNlg

What\'s R30 supposed to achieve? This is right at the top of the
schematic, btw.

** It provides peak current limiting at the moment the unit is connected to a DC supply - plus a measure of noise filtering thereafter in conjunction with the 2200uF electro.
Should be a composition or WW type, not carbon film, to survive the energy in such surges.
Nothing strange about the original film resistor failing open and invisibly when subjected to 13A spikes lasting a few milliseconds.

I\'ll second that. British power plugs have a built-in fuse and R30 makes it less likely that this fuse would blow on switch-on.

** Huh ?????

Attempted humour ?

...... Phil

The fuses in British plugs are slow blow and frequently take up to 6
minutes to blow in an over-current event (excepting short-circuits and
the like). Sorry, Bill, R30 won\'t protect the plug fuse and if I may
say so, it\'s a very strange claim to make coming from such an expert
as yourself.

 

[Anthony William Sloman]

On Monday, August 14, 2023 at 6:35:17 PM UTC+10, Dan Green wrote:

On Sun, 13 Aug 2023 17:44:49 -0400, ehsjr <eh...@verizon.net> wrote:

On 8/13/2023 12:58 PM, Cursitor Doom wrote:
On Sun, 13 Aug 2023 12:51:09 -0400, legg <le...@nospam.magma.ca> wrote:

Cheaper than a fuse.

Yeah, but ONE OHM? How much current is that going to limit?

Phil nailed it.
Which Phil? THere are 2 on this thread and they each say totally
different things. Phil A says the resistor *does* limiit inrush current
and Phil H says it does essentially *nothing* to limit inrush. I know
who *my* money\'s on (hint: not the guy who thinks RF and audio are the
same thing) .

Actually the guy who work in audio, and know how often RF issues come up in studio work, versus the guy who is a physicist.

--
Bill Sloman, Sydney

 

[Anthony William Sloman]

On Monday, August 14, 2023 at 9:53:17 PM UTC+10, Cursitor Doom wrote:

On Mon, 14 Aug 2023 03:13:06 -0700 (PDT), Phil Allison <palli...@gmail.com> wrote:
Anthony William Sloman wrote:
Phil Allison wrote:
Cursitor Doom wrote:

Sip>

** It provides peak current limiting at the moment the unit is connected to a DC supply - plus a measure of noise filtering thereafter in conjunction with the 2200uF electro.
Should be a composition or WW type, not carbon film, to survive the energy in such surges.
Nothing strange about the original film resistor failing open and invisibly when subjected to 13A spikes lasting a few milliseconds.

I\'ll second that. British power plugs have a built-in fuse and R30 makes it less likely that this fuse would blow on switch-on.

** Huh ?????

Attempted humour?

I\'ve worked in the UK and know about this. Phil hasn\'t and might not.

The fuses in British plugs are slow blow and frequently take up to 6
minutes to blow in an over-current event (excepting short-circuits and
the like).

Slow blow doesn\'t mean that they they can\'t get damaged by repeated spikes.

> Sorry, Bill, R30 won\'t protect the plug fuse and if I may say so, it\'s a very strange claim to make coming from such an expert as yourself.

You can say what you like - I\'m infinitely more worried about Phil\'s claim that I\'ve got it wrong, which isn\'t all that worried. You merely are the dimmest of dim jerks.

--
Bill Sloman, Sydney

 

[Cursitor Doom]

On Mon, 14 Aug 2023 05:05:36 -0700 (PDT), Anthony William Sloman
<bill.sloman@ieee.org> wrote:

On Monday, August 14, 2023 at 9:53:17?PM UTC+10, Cursitor Doom wrote:
On Mon, 14 Aug 2023 03:13:06 -0700 (PDT), Phil Allison <palli...@gmail.com> wrote:
Anthony William Sloman wrote:
Phil Allison wrote:
Cursitor Doom wrote:

Sip
** It provides peak current limiting at the moment the unit is connected to a DC supply - plus a measure of noise filtering thereafter in conjunction with the 2200uF electro.
Should be a composition or WW type, not carbon film, to survive the energy in such surges.
Nothing strange about the original film resistor failing open and invisibly when subjected to 13A spikes lasting a few milliseconds.

I\'ll second that. British power plugs have a built-in fuse and R30 makes it less likely that this fuse would blow on switch-on.

** Huh ?????

Attempted humour?

I\'ve worked in the UK and know about this. Phil hasn\'t and might not.

The fuses in British plugs are slow blow and frequently take up to 6
minutes to blow in an over-current event (excepting short-circuits and
the like).

Slow blow doesn\'t mean that they they can\'t get damaged by repeated spikes.

Nonsense. I\'ve never even heard of a mains fuse being damaged by
spikes in the supply line. Fuses shrug off that kind of thing
indefinitely. Then to go further and claim that a surge in current in
the 13V supply to a 4W amp IC can damage the mains fuse over time is
quite frankly ludicrous.

Sorry, Bill, R30 won\'t protect the plug fuse and if I may say so, it\'s a very strange claim to make coming from such an expert as yourself.

You can say what you like - I\'m infinitely more worried about Phil\'s claim that I\'ve got it wrong, which isn\'t all that worried. You merely are the dimmest of dim jerks.

If I\'m the dimmest dim jerks but correct in dismissing your claim,
then that doesn\'t say much for your level of expertise in this area.