Good advice from you both on battery fusing, particularly in vehicles, but
you've drifted off the subject a little.
Chris W7CTH said:
Hi, I am ready to apply 12v for the first time to my new K3.
I would use a current-limited power supply to connect up ANY equipment for
the first time. No fuse
David Cutter wrote:
I would use a current-limited power supply to connect up ANY equipment
for the first time. No fuse is as fast as electronic limiting.
Even the fastest semiconductor fuses require a huge overload to achieve
a sluggish response. Busman 25A fuse: 340A^2t. I'm not an expert,
From: David Cutter d.cut...@ntlworld.com
To: d...@w3fpr.com; Tom W8JI w...@w8ji.com
Cc: elecraft@mailman.qth.net; Chris Hembree w7...@yahoo.com
Sent: Fri, August 13, 2010 12:33:33 AM
Subject: Re: [Elecraft] K3 inline fuse
Good advice from you both on battery fusing, particularly in vehicles
On Fri, 13 Aug 2010 11:08:04 +0100, Ian White GM3SEK wrote:
The other important point is that fuses provide ZERO protection until
AFTER they have blown. In the life and death of a semiconductor, even a
few milliseconds is a very long time indeed.
Yes. On the other hand, boards are all
Ian wrote...
The other important point is that fuses provide ZERO protection until
AFTER they have blown. In the life and death of a semiconductor, even a
few milliseconds is a very long time indeed.
I like to tell the story about a series of tests we did when I worked at
Fairchild, in
A transistor is the fastest fuse on 3 legs, beats a 2-legged fuse any day.
David
G3UNA
I like to tell the story about a series of tests we did when I worked at
Fairchild, in
Silicon Valley. Our little VHF silicon transistors were very expensive,
and quite
fragile. We tested many fuses
The transistor is the most probable reason for the fuse blowing but the fuse
may save the other components and semi conductors as well as the circuit board.
The original query stated he would be using an Astron 35 which has a current
limiter but limiting the current to 35 amps will still allow
If you do not have an **adjustable** current limited supply, do what I do on
the bench.
I have a 35 amp limited supply on the bench, and my 13.8 volt buss has jacks
that are direct, through a 10 ohm 10 watt resistor, and through a second 10
ohm in series with that.
I can get a really good
One thing that hasn't been mentioned is that the K3 has a built-in 6A
fuse for the basic rig and a separate 20A circuit breaker for the
KPA3. So it's not like there's no protection at all between the APP
connector and the internal circuits.
73
--
Joe KB8AP
On Aug 13, 2010, at 9:02 AM,
Amen! Best so far.
Let´s move on.
/ James
-
On 2010-08-13 17:01, David Cutter wrote:
A transistor is the fastest fuse on 3 legs, beats a 2-legged fuse any day.
David
G3UNA
I like to tell the story about a series of tests we did when I worked at
Fairchild, in
Silicon Valley.
You are much better off using the current limiting feature of your dc
supply. A fuse is not fast enough to protect any electronic circuitry.
Strictly speaking a fuse in line is rated to protect the cable in the event
of a short circuit in the rig which would be a very big fuse, far bigger
I completely agree with you. The inline fuses are there for mobile
installations where you have a direct connection to the car battery. On my
ICOM radios I have always shortened the power cable removing the inline fuse
in the process.
AB2TC - Knut
David Cutter wrote:
You are much better off
,
that will protect you adequately. When the K3 comes alive, you can increase
the current limit to operating conditions. I hope this helps.
Mel
--- On Thu, 8/12/10, ab2tc ab...@arrl.net wrote:
From: ab2tc ab...@arrl.net
Subject: Re: [Elecraft] K3 inline fuse
To: elecraft@mailman.qth.net
Date
The best method is Wayne's suggestion from way back:
In both Neg and Pos leads, supply a fuseholder and fuse. I use the
stubby fuses from Motorola @ 30A, you should use something like
that. These are T-rated, meaning they're designed to open with a DC
load. Don't use a fuse out of your home's
Positive lead fuses are a good idea.
Negative lead fuses never were a good idea unless the radio has a totally
floating negative buss.
If the negative lead fuse to the radio opens for any reason all the negative
lead current for the radio will flow through the negative lead of any
accessories
Tom,
You are absolutely correct. Take a mobile situation - the radio's power
ground is connected to the transceiver chassis ground, as is the coax
shield, microphone shield and other stuff. All that stuff can (and
will) connect to the vehicle chassis at some point. I know the coax
will
On 8/11/2010 6:32 PM, Chris Hembree wrote:
Hi, I am ready to apply 12v for the first time to my new K3. Should I have a
inline fuse on the DC to the K3? and if so what amp.
Just don't look right not to have a fuse inline.
Thanks
Chris W7CTH
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