Resistor in DC supply line...

[legg]

On Mon, 14 Aug 2023 00:55:14 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

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

Googling \'F2887103\' (- in the Yaesu FT-763R transceiver) gives you
all the info you\'ll ever want about R30, in this 30yr old device.

RL

 

[John Larkin]

On Mon, 14 Aug 2023 09:35:06 +0100, Dan Green <dhg99908@hotmail.se>
wrote:

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) .

A piece of gear that has a 12 volt internal power supply and some
loads should not have giant current surges; the supply should ramp up
at some sensible rate and current limit.

We do expect huge surges, visible sparks, when a live external DC
supply, a battery or a wall wart, is plugged into our box. That\'s
worth thinking about.

Warts can also be the wrong voltage - they all look alike - or even,
rarely, the wrong polarity.

 

[Anthony William Sloman]

On Monday, August 14, 2023 at 10:47:50 PM UTC+10, Cursitor Doom wrote:

On Mon, 14 Aug 2023 05:05:36 -0700 (PDT), Anthony William Sloman
bill....@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.

And you\'ve never heard that climate change is real and CO2 levels really are rising. You should have done but you\'ve worked out how to close your ears to information you don\'t want to hear.

> 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.

This is coming from the guy who prefers to believe crap CO2 level measurements from the 1890\'s to Charles Keeling\'s serious CO2 monitoring that started in 1958.
Stuff has got to be frankly ludicrous before you\'ll even begin to take it seriously.
Fuses do fail for no obvious reason from time to time and cumulative damage from spike loads is as good an explanation as any.

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.

Big if. You really are the dimmest of dim jerks and you really are unlikely to be correct in this particular instance. You certainly don\'t make a habit of getting stuff right.

--
Bill Sloman, Sydney

 

[Jan Panteltje]

On a sunny day (Mon, 14 Aug 2023 06:55:58 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<o7ckditkl9d7dsdo2o0t5egro9i37qknvc@4ax.com>:

On Mon, 14 Aug 2023 09:35:06 +0100, Dan Green <dhg99908@hotmail.se
wrote:

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) .

A piece of gear that has a 12 volt internal power supply and some
loads should not have giant current surges; the supply should ramp up
at some sensible rate and current limit.

We do expect huge surges, visible sparks, when a live external DC
supply, a battery or a wall wart, is plugged into our box. That\'s
worth thinking about.

Warts can also be the wrong voltage - they all look alike - or even,
rarely, the wrong polarity.

The adjustable warts I have have a connector that can be plugged in the reverse way, even for USB..
https://panteltje.nl/pub/universal_wart_IXIMG_0879.JPG

 

[Don]

legg wrote:

<snip>

Googling \'F2887103\' (- in the Yaesu FT-763R transceiver) gives you
all the info you\'ll ever want about R30, in this 30yr old device.

My search returns variations of three webpages: a 2016 ad for an audio
board for sale, an Austrialian ham who replaced his audio board because
R30 failed open, and a Yaesu FT-736R Operating Manual.
Info about the purpose of R30 is wanted. But my search returns no
pertinent info.
A lack of disclosure about design details doesn\'t surprise me. Given
a vendor\'s typical reluctance to share such specifics.

Danke,

--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

 

[Dan Green]

On Mon, 14 Aug 2023 15:39:29 -0000 (UTC), \"Don\" <g@crcomp.net> wrote:

legg wrote:

snip

Googling \'F2887103\' (- in the Yaesu FT-763R transceiver) gives you
all the info you\'ll ever want about R30, in this 30yr old device.

My search returns variations of three webpages: a 2016 ad for an audio
board for sale, an Austrialian ham who replaced his audio board because
R30 failed open, and a Yaesu FT-736R Operating Manual.
Info about the purpose of R30 is wanted. But my search returns no
pertinent info.

Same here. That suggestion was a waste of time.

 

[ehsjr]

On 8/13/2023 6:31 PM, Phil Hobbs 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.

I\'ve no idea what the main inrush limiter is in the transceiver.
Regardless, the resistor will limit inrush current to the cap at
turn on (assuming of course that the cap is discharged at that
time). And that repetitive inrush current stresses the resistor.
There may well be other circuitry to handle inrush to the transceiver,
but the fact remains that the discharged 2200uf will try to draw
enormous current through R30 from the 13.8 supply. If we assume
worst case no other limiting, 14V input, R30 exactly 1 ohm and no
other resistance, R30 will limit current to 14 AMPs max, reducing
exponentially with time until the cap is ~fully charged in 11 ms.
(Or until R30 fails). You know all that, but other readers may not.

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

Actually ~.2 J not ~.4 J. Even so, the R lasted ~35 years in spite
of being under sized. And it _is_ too small based on what the schematic
shows. Apparently that is a known failure point in the FT 736.

Ed

Cheers

Phil Hobbs

 

[Cursitor Doom]

On Mon, 14 Aug 2023 08:00:22 -0700 (PDT), Anthony William Sloman
<bill.sloman@ieee.org> wrote:

On Monday, August 14, 2023 at 10:47:50?PM UTC+10, Cursitor Doom wrote:
On Mon, 14 Aug 2023 05:05:36 -0700 (PDT), Anthony William Sloman
bill....@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.

And you\'ve never heard that climate change is real and CO2 levels really are rising. You should have done but you\'ve worked out how to close your ears to information you don\'t want to hear.

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.

This is coming from the guy who prefers to believe crap CO2 level measurements from the 1890\'s to Charles Keeling\'s serious CO2 monitoring that started in 1958.
Stuff has got to be frankly ludicrous before you\'ll even begin to take it seriously.
Fuses do fail for no obvious reason from time to time and cumulative damage from spike loads is as good an explanation as any.

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.

Big if. You really are the dimmest of dim jerks and you really are unlikely to be correct in this particular instance. You certainly don\'t make a habit of getting stuff right.

Maybe not in general, but I\'ve got you this time, Bill. You made a
stoopid observation and now you\'re trying to cover your tracks by
diverting the subject into climate change. That won\'t wash. You\'ve
been exposed as a bullshitter once again.

 

[Phil Hobbs]

On 2023-08-14 16:43, ehsjr wrote:> On 8/13/2023 6:31 PM, Phil Hobbs 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.

I\'ve no idea what the main inrush limiter is in the transceiver.
Regardless, the resistor will limit inrush current to the cap at
turn on (assuming of course that the cap is discharged at that
time). And that repetitive inrush current stresses the resistor.
There may well be other circuitry to handle inrush to the transceiver,
but the fact remains that the discharged 2200uf will try to draw
enormous current through R30 from the 13.8 supply. If we assume
worst case no other limiting, 14V input, R30 exactly 1 ohm and no
other resistance, R30 will limit current to 14 AMPs max, reducing
exponentially with time until the cap is ~fully charged in 11 ms.
(Or until R30 fails). You know all that, but other readers may not.


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

Actually ~.2 J not ~.4 J.

Right you are, 1/2 CV**2. My bad.

Even so, the R lasted ~35 years in spite
of being under sized. And it _is_ too small based on what the schematic
shows. Apparently that is a known failure point in the FT 736.

Because it\'s not actually seeing that big an inrush.

It\'s unlikely that a 1/4 W film resistor is going to survive having even
200 mJ dumped into it in a couple of milliseconds. For instance, the
graph on P. 5 of this datasheet

https://www.yageo.com/upload/media/product/productsearch/datasheet/lr/YAGEO%20CFR_datasheet_2022v1.pdf

shows a maximum rating for a 1/4 W resistor of just over 10W for 2 ms.
There are metal film ones (Yageo MFR series) that are a bit higher, but
not 100W. (You might not blow up an RN55C 1/4 W right away, but the
resistor in the photo is one of the usual cheap dog bone variety.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[boB]

On Mon, 14 Aug 2023 17:59:34 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2023-08-14 16:43, ehsjr wrote:> On 8/13/2023 6:31 PM, Phil Hobbs 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.

I\'ve no idea what the main inrush limiter is in the transceiver.
Regardless, the resistor will limit inrush current to the cap at
turn on (assuming of course that the cap is discharged at that
time). And that repetitive inrush current stresses the resistor.
There may well be other circuitry to handle inrush to the transceiver,
but the fact remains that the discharged 2200uf will try to draw
enormous current through R30 from the 13.8 supply. If we assume
worst case no other limiting, 14V input, R30 exactly 1 ohm and no
other resistance, R30 will limit current to 14 AMPs max, reducing
exponentially with time until the cap is ~fully charged in 11 ms.
(Or until R30 fails). You know all that, but other readers may not.


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

Actually ~.2 J not ~.4 J.

Right you are, 1/2 CV**2. My bad.

Even so, the R lasted ~35 years in spite
of being under sized. And it _is_ too small based on what the schematic
shows. Apparently that is a known failure point in the FT 736.

Because it\'s not actually seeing that big an inrush.

It\'s unlikely that a 1/4 W film resistor is going to survive having even
200 mJ dumped into it in a couple of milliseconds. For instance, the
graph on P. 5 of this datasheet

https://www.yageo.com/upload/media/product/productsearch/datasheet/lr/YAGEO%20CFR_datasheet_2022v1.pdf

shows a maximum rating for a 1/4 W resistor of just over 10W for 2 ms.
There are metal film ones (Yageo MFR series) that are a bit higher, but
not 100W. (You might not blow up an RN55C 1/4 W right away, but the
resistor in the photo is one of the usual cheap dog bone variety.)

Cheers

Phil Hobbs

I was looking for the exact data sheet for a particular family of smt
resistors we use, (Yageo is one of them) but found this quickly on
Digikey. Check out the pulse graph. A 1206 size is rated at ALMOST
100 watts for 1ms (0.001 s)

https://www.digikey.com/Site/Global/Layouts/DownloadPdf.ashx?pdfUrl=BEFFAA7BBB584DEF8A637493630A90A7

boB

 

[Phil Allison]

Cursitor Doom wrote:
--------------------------------------

** 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.

** Overcurrent pulse failure of R30 requires the 13.8V DC supply to appear very suddenly - as with \"hot plugging\" a battery or external DC supply to the DC socket on the back of the radio. Also hot plugging that audio PCB onto the internal DC rail would do the same.
Normal mains on-off cycling would not be likely to do such damage as it takes a short time for the internal DC rails to rise to full voltage.
Maybe helps explain the reported 35 year delay.


....... Phil

 

[Phil Hobbs]

boB <boB@K7IQ.com> wrote:

On Mon, 14 Aug 2023 17:59:34 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2023-08-14 16:43, ehsjr wrote:> On 8/13/2023 6:31 PM, Phil Hobbs 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.

I\'ve no idea what the main inrush limiter is in the transceiver.
Regardless, the resistor will limit inrush current to the cap at
turn on (assuming of course that the cap is discharged at that
time). And that repetitive inrush current stresses the resistor.
There may well be other circuitry to handle inrush to the transceiver,
but the fact remains that the discharged 2200uf will try to draw
enormous current through R30 from the 13.8 supply. If we assume
worst case no other limiting, 14V input, R30 exactly 1 ohm and no
other resistance, R30 will limit current to 14 AMPs max, reducing
exponentially with time until the cap is ~fully charged in 11 ms.
(Or until R30 fails). You know all that, but other readers may not.


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

Actually ~.2 J not ~.4 J.

Right you are, 1/2 CV**2. My bad.

Even so, the R lasted ~35 years in spite
of being under sized. And it _is_ too small based on what the schematic
shows. Apparently that is a known failure point in the FT 736.

Because it\'s not actually seeing that big an inrush.

It\'s unlikely that a 1/4 W film resistor is going to survive having even
200 mJ dumped into it in a couple of milliseconds. For instance, the
graph on P. 5 of this datasheet

https://www.yageo.com/upload/media/product/productsearch/datasheet/lr/YAGEO%20CFR_datasheet_2022v1.pdf

shows a maximum rating for a 1/4 W resistor of just over 10W for 2 ms.
There are metal film ones (Yageo MFR series) that are a bit higher, but
not 100W. (You might not blow up an RN55C 1/4 W right away, but the
resistor in the photo is one of the usual cheap dog bone variety.)

Cheers

Phil Hobbs


I was looking for the exact data sheet for a particular family of smt
resistors we use, (Yageo is one of them) but found this quickly on
Digikey. Check out the pulse graph. A 1206 size is rated at ALMOST
100 watts for 1ms (0.001 s)

Of course pulse-withstanding resistors exist. They’re commonly used with
large caps to get the right ESR to stabilize a voltage regulator, for
instance. (*)

But that piddly axial thing at R30 ain’t one of them.

Cheers

Phil Hobbs

(*) Putting the resistor in series with the cap preserves the load
regulation, and to survive an output short it has to be a pulse-rated type.



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

 

[Anthony William Sloman]

On Tuesday, August 15, 2023 at 7:37:43 AM UTC+10, Cursitor Doom wrote:

On Mon, 14 Aug 2023 08:00:22 -0700 (PDT), Anthony William Sloman
bill....@ieee.org> wrote:
On Monday, August 14, 2023 at 10:47:50?PM UTC+10, Cursitor Doom wrote:
On Mon, 14 Aug 2023 05:05:36 -0700 (PDT), Anthony William Sloman
bill....@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.

And you\'ve never heard that climate change is real and CO2 levels really are rising. You should have done but you\'ve worked out how to close your ears to information you don\'t want to hear.

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.

This is coming from the guy who prefers to believe crap CO2 level measurements from the 1890\'s to Charles Keeling\'s serious CO2 monitoring that started in 1958.
Stuff has got to be frankly ludicrous before you\'ll even begin to take it seriously.
Fuses do fail for no obvious reason from time to time and cumulative damage from spike loads is as good an explanation as any.

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.

Big if. You really are the dimmest of dim jerks and you really are unlikely to be correct in this particular instance. You certainly don\'t make a habit of getting stuff right.

Maybe not in general, but I\'ve got you this time, Bill. You made a
stoopid observation and now you\'re trying to cover your tracks by
diverting the subject into climate change. That won\'t wash. You\'ve
been exposed as a bullshitter once again.

Except that it wasn\'t a stupid observation, and we\'d got onto your credibility which is essentially zero because of your enthusiasm for to touting attention-getting nonsense. Your enthusiasm for climate change denial is the obvious example. but your enthusiasm for telling us about the globalist conspiracy and George Soros isn\'t far behind.

Back in your box.

--
Bill Sloman, Sydney

 

[legg]

On Mon, 14 Aug 2023 19:15:19 +0100, Dan Green <dhg99908@hotmail.se>
wrote:

On Mon, 14 Aug 2023 15:39:29 -0000 (UTC), \"Don\" <g@crcomp.net> wrote:

legg wrote:

snip

Googling \'F2887103\' (- in the Yaesu FT-763R transceiver) gives you
all the info you\'ll ever want about R30, in this 30yr old device.

My search returns variations of three webpages: a 2016 ad for an audio
board for sale, an Austrialian ham who replaced his audio board because
R30 failed open, and a Yaesu FT-736R Operating Manual.
Info about the purpose of R30 is wanted. But my search returns no
pertinent info.

Same here. That suggestion was a waste of time.

Not as big a waste of time as discussing repair methods with CD
on SED.

RL

 

[Phil Hobbs]

On 2023-08-15 10:11, Don Y wrote:> On 8/14/2023 7:45 AM, Phil Hobbs wrote:

The boards don\'t have to be particularly sturdy as
they will be supported completely by their undersides.

What sort of material might be suitable for this?

[I\'m only looking for small quantities -- hundreds.
I\'ll let someone else refine the process for bigger
quantities (with commensurate investments]

We’ve used Dirty PCBs for stuff like that in the long-ago time.

https://dirtypcbs.com

Dunno if they’ve gone too far upmarket since.

\"Stuff like that\" meaning \"dirt cheap\", \"flimsy\"? Or, \"unusual
outlines\"?

Dirt cheap, solder mask and silk screen optional, PTH also optional. We
built some breakout boards for prototyping.

(Small rectangular pads on a grid of 0.5 x 0.65 mm are super useful too.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[ehsjr]

On 8/14/2023 5:59 PM, Phil Hobbs wrote:

On 2023-08-14 16:43, ehsjr wrote:> On 8/13/2023 6:31 PM, Phil Hobbs 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.

I\'ve no idea what the main inrush limiter is in the transceiver.
Regardless, the resistor will limit inrush current to the cap at
turn on (assuming of course that the cap is discharged at that
time).  And that repetitive inrush current stresses the resistor.
There may well be other circuitry to handle inrush to the transceiver,
but the fact remains that the discharged 2200uf will try to draw
enormous current through R30 from the 13.8 supply.  If we assume
worst case no other limiting, 14V input, R30 exactly 1 ohm and no
other resistance, R30 will limit current to 14 AMPs max, reducing
exponentially with time until the cap is ~fully charged in 11 ms.
(Or until R30 fails). You know all that, but other readers may not.


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

Actually ~.2 J not ~.4 J.

Right you are, 1/2 CV**2.  My bad.

Even so, the R lasted ~35 years in spite
of being under sized. And it _is_ too small based on what the schematic
shows. Apparently that is a known failure point in the FT 736.

Because it\'s not actually seeing that big an inrush.

You are right, of course. We don\'t know how much R30 actually
\"sees\" - wire/trace inductance and resistance, power supply
\"ramp-up\" time, other factors(?) that limit the current are
not known.

It\'s the repetitive surges over time (~35 years in this case)
that probably killed R30, not how much current 1 ohm limits
in a single event (to paraphrase the question).

It does beg the question (the answer is, \"you\'d have to the
designer\") \"why those values for the low pass filter?\"

Maybe they had a boatload of 1 ohm 1/4w R\'s on hand.
I dunno.

Ed

It\'s unlikely that a 1/4 W film resistor is going to survive having even
200 mJ dumped into it in a couple of milliseconds.  For instance, the
graph on P. 5 of this datasheet

https://www.yageo.com/upload/media/product/productsearch/datasheet/lr/YAGEO%20CFR_datasheet_2022v1.pdf

shows a maximum rating for a 1/4 W resistor of just over 10W for 2 ms.
There are metal film ones (Yageo MFR series) that are a bit higher, but
not 100W.  (You might not blow up an RN55C 1/4 W right away, but the
resistor in the photo is one of the usual cheap dog bone variety.)

Cheers

Phil Hobbs

 

[boB]

On Tue, 15 Aug 2023 03:39:01 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

boB <boB@K7IQ.com> wrote:
On Mon, 14 Aug 2023 17:59:34 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2023-08-14 16:43, ehsjr wrote:> On 8/13/2023 6:31 PM, Phil Hobbs 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.

I\'ve no idea what the main inrush limiter is in the transceiver.
Regardless, the resistor will limit inrush current to the cap at
turn on (assuming of course that the cap is discharged at that
time). And that repetitive inrush current stresses the resistor.
There may well be other circuitry to handle inrush to the transceiver,
but the fact remains that the discharged 2200uf will try to draw
enormous current through R30 from the 13.8 supply. If we assume
worst case no other limiting, 14V input, R30 exactly 1 ohm and no
other resistance, R30 will limit current to 14 AMPs max, reducing
exponentially with time until the cap is ~fully charged in 11 ms.
(Or until R30 fails). You know all that, but other readers may not.


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

Actually ~.2 J not ~.4 J.

Right you are, 1/2 CV**2. My bad.

Even so, the R lasted ~35 years in spite
of being under sized. And it _is_ too small based on what the schematic
shows. Apparently that is a known failure point in the FT 736.

Because it\'s not actually seeing that big an inrush.

It\'s unlikely that a 1/4 W film resistor is going to survive having even
200 mJ dumped into it in a couple of milliseconds. For instance, the
graph on P. 5 of this datasheet

https://www.yageo.com/upload/media/product/productsearch/datasheet/lr/YAGEO%20CFR_datasheet_2022v1.pdf

shows a maximum rating for a 1/4 W resistor of just over 10W for 2 ms.
There are metal film ones (Yageo MFR series) that are a bit higher, but
not 100W. (You might not blow up an RN55C 1/4 W right away, but the
resistor in the photo is one of the usual cheap dog bone variety.)

Cheers

Phil Hobbs


I was looking for the exact data sheet for a particular family of smt
resistors we use, (Yageo is one of them) but found this quickly on
Digikey. Check out the pulse graph. A 1206 size is rated at ALMOST
100 watts for 1ms (0.001 s)


Of course pulse-withstanding resistors exist. They’re commonly used with
large caps to get the right ESR to stabilize a voltage regulator, for
instance. (*)

But that piddly axial thing at R30 ain’t one of them.

Yep. I\'m sure that axial TH resistors exist but we rather use SMT cuz
when you get one wrong, almost always guarranteed to get all of them
wrong

We specify all resistors 100 Ohms and below (usually) to have a decent
pulse rating like, 50 watts per ms for gate drive etc.

Even the so called zero Ohm resistors are specified to be 20 milliohms
which break a lot. I try to design those out if I know I won\'t be
using a real part there in the future because of the unreliable
nature.

boB

Cheers

Phil Hobbs

(*) Putting the resistor in series with the cap preserves the load
regulation, and to survive an output short it has to be a pulse-rated type.

 

[Ricky]

On Tuesday, August 15, 2023 at 5:14:57 PM UTC-4, boB wrote:

On Tue, 15 Aug 2023 03:39:01 -0000 (UTC), Phil Hobbs
pcdhSpamM...@electrooptical.net> wrote:

boB <b...@K7IQ.com> wrote:
On Mon, 14 Aug 2023 17:59:34 -0400, Phil Hobbs
pcdhSpamM...@electrooptical.net> wrote:

On 2023-08-14 16:43, ehsjr wrote:> On 8/13/2023 6:31 PM, Phil Hobbs wrote:
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. 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.

I\'ve no idea what the main inrush limiter is in the transceiver.
Regardless, the resistor will limit inrush current to the cap at
turn on (assuming of course that the cap is discharged at that
time). And that repetitive inrush current stresses the resistor.
There may well be other circuitry to handle inrush to the transceiver,
but the fact remains that the discharged 2200uf will try to draw
enormous current through R30 from the 13.8 supply. If we assume
worst case no other limiting, 14V input, R30 exactly 1 ohm and no
other resistance, R30 will limit current to 14 AMPs max, reducing
exponentially with time until the cap is ~fully charged in 11 ms.
(Or until R30 fails). You know all that, but other readers may not.


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

Actually ~.2 J not ~.4 J.

Right you are, 1/2 CV**2. My bad.

Even so, the R lasted ~35 years in spite
of being under sized. And it _is_ too small based on what the schematic
shows. Apparently that is a known failure point in the FT 736.

Because it\'s not actually seeing that big an inrush.

It\'s unlikely that a 1/4 W film resistor is going to survive having even
200 mJ dumped into it in a couple of milliseconds. For instance, the
graph on P. 5 of this datasheet

https://www.yageo.com/upload/media/product/productsearch/datasheet/lr/YAGEO%20CFR_datasheet_2022v1.pdf

shows a maximum rating for a 1/4 W resistor of just over 10W for 2 ms..
There are metal film ones (Yageo MFR series) that are a bit higher, but
not 100W. (You might not blow up an RN55C 1/4 W right away, but the
resistor in the photo is one of the usual cheap dog bone variety.)

Cheers

Phil Hobbs


I was looking for the exact data sheet for a particular family of smt
resistors we use, (Yageo is one of them) but found this quickly on
Digikey. Check out the pulse graph. A 1206 size is rated at ALMOST
100 watts for 1ms (0.001 s)


Of course pulse-withstanding resistors exist. They’re commonly used with
large caps to get the right ESR to stabilize a voltage regulator, for
instance. (*)

But that piddly axial thing at R30 ain’t one of them.
Yep. I\'m sure that axial TH resistors exist but we rather use SMT cuz
when you get one wrong, almost always guarranteed to get all of them
wrong

We specify all resistors 100 Ohms and below (usually) to have a decent
pulse rating like, 50 watts per ms for gate drive etc.

Even the so called zero Ohm resistors are specified to be 20 milliohms
which break a lot. I try to design those out if I know I won\'t be
using a real part there in the future because of the unreliable
nature.

I saw a data sheet for a zero ohm resistor that specified the value to be ±10%.

I\'d like to see them do the calculations on that one!

--

Rick C.

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

 

[Don]

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.

After kicking this around in a FT-736R forum someone mentioned how R30
looks like a decouple. And it seems on the money, to me.

A quick glance at the UPC2002H datasheet App Notes

<https://datasheet.datasheetarchive.com/originals/scans/Scans-063/DSA2IH00127206.pdf>

does not reveal any hints as to the purpose of R30.

Regardless, Figure 7 in AD\'s MT-101 TUTORIAL Decoupling Techniques

<https://www.analog.com/media/en/training-seminars/tutorials/MT-101.pdf>

shows a small series resistance close to an IC power line as a way to
reduce Q. The tutorial goes on to say:

However, a decoupling network composed of a 100 μF capacitor
and a 1 μH inductor resonates at 16 kHz. Left unchecked, this
can present a resonance problem if this frequency appears on
the power line. The effect can be minimized by lowering the Q
of the circuit. This is most easily done by inserting a small
resistance (~10 Ω) in the power line close to the IC, as shown
in the right case. The resistance should be kept as low as
possible to minimize the IR drop across the resistor. An
alternative to a resistor is a small ferrite bead which appears
primarily resistive at the resonant frequency.

Long story short, decoupling seems to be the purpose of R30.

Danke,

--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.