[Boatanchors] Inrush Current Limiters

Mon Apr 30 07:18:09 EDT 2018

Bill,

You are welcome and the added heat from an inrush suppressor is not that high.  In the V2 it won’t have anywhere close to a significant impact on the operating temperature of the transmitter.  Typical dissipation within the device will be under 2 watts so total heat output is similar to that of a dial lamp.  The heat caution is because all of this heat dissipation is within a small disc you don’t want it touching a low temperature plastic item or have it snugged up against electrolytic caps or other components that have accelerated deterioration due to increased operating temperature.  Basically use the same cautions in mounting these devices as you would with a small power resistor.

In many pieces of gear there is a length of wire running from the fuse holder to a terminal strip and in these cases I will normally replace that wire with the inrush device.  In other cases I will use an existing terminal strip or add another strip using existing mounting holes.

Rodger WQ9E

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________________________________
From: Bill Stewart <cwopr at embarqmail.com>
Sent: Monday, April 30, 2018 5:58:28 AM
To: Rodger Singley
Cc: boatanchors
Subject: Re: Inrush Current Limiters

Roger, Brian, Rob and Dennis, thanks for the explanations and comments.
In my case, the fuse blew when the fil. was turned on and that's when the occasional
thumping goes on (also turns on the low voltage B+), when I turn on the xmtr. If the
fuse blows occasionally, then that indicates a big current surge which, as Rodger
points out, causes those nuisance fuse pops....not easy to replace with the V2. Plus
I guess it would not treat the pwr xfmr to good. Although, the V2 xfmrs look like stout
ones. As far as mounting a fuse outside, Rodger has a good idea. I was thinking along
that line....a small project box attached to a screw on the rear...no added hole...this V2
is in nice condx. I would not be too happy abt the added heat from the ICL...guess that
could be mounted in with the fuse externally.
73 de Bill K4JYS

________________________________
From: "Rodger Singley" <wq9nsc at live.com>
To: "cwopr" <cwopr at embarqmail.com>
Cc: "boatanchors" <boatanchors at mailman.qth.net>
Sent: Sunday, April 29, 2018 6:34:00 AM
Subject: RE: Inrush Current Limiters

One of the advantages of using inrush limiters is it reduces the “nuisance” blowing of fuses.  Depending upon the point in the AC waveform when you throw the switch you may have a high inrush current as the primary builds a magnetic field and the “thump” sound is from the abrupt change in field; Hallicrafters SX-42 and SX-62 receivers are famous for making this sound.

I use NTC inrush limiters from Mouser:  https://www.mouser.com/search/refine.aspx?N=18356455<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.mouser.com%2Fsearch%2Frefine.aspx%3FN%3D18356455&data=02%7C01%7C%7C50b61d0394c349864f6a08d5ae895069%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636606827132786432&sdata=I8HekszgEAFElGeVZGwOeUHZXHKNaavHkyRXQXIGD%2Fw%3D&reserved=0>  They are inexpensive devices and a lot of rigs that go across my bench get them.  I try to size them so that the expected full load current is around 70-80% of the component’s rated full load current.  Primary specs are current rating and cold resistance; the higher the cold resistance the greater the inrush limiting but there is no reason to go crazy here as it doesn’t take a lot of resistance to greatly tame the inrush current.

These devices can be used in series for even more reduction in inrush current but this is not something you need to do with vintage gear.  NEVER try to put them in parallel to increase total current rating because current rating will NOT divide equally; series is OK but never parallel.

The biggest caution in use is they do run very hot so don’t mount them next to or directly below a heat sensitive component.

For the fusing I hate drilling holes in vintage gear and another option is using a small plastic “project” box inline with the line cord and mount a fuse in the box.  It looks a little clunky but in use it is hidden behind the gear and doesn’t require drilling or other modification to the gear.  I did this years ago when I built a power cord for my Johnson Desk KW for use in testing after I completely rebuilt the unit.  The Desk KW has no provision for fuses for the plate transformer and the only fuses in the unit are for the low power supplies, it depends upon the branch breaker in the house for protection.  I built a power cord with a box and two fuse holders so that I could easily insert lower current fuses during initial testing and then fuse it properly in use without depending upon it tripping the branch breaker.

Rodger WQ9E

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________________________________
From: boatanchors-bounces at mailman.qth.net <boatanchors-bounces at mailman.qth.net> on behalf of Bill Stewart <cwopr at embarqmail.com>
Sent: Saturday, April 28, 2018 4:42:08 PM
To: Dennis DuVall
Cc: boatanchors
Subject: Re: [Boatanchors] Inrush Current Limiters

One thing is the thump from the inductive kick when turning the fils. on...not every time
but occasionally. I haven't finished my cking, but that may have caused the 5A fuse to blow
(hopefully and not something else). I have had it in service for close to 20 years and this
is the first fuse to blow. It is just too hvy to hve to change the fuse...that's why I am
either looking at a ICL or putting the fuse holder on the rear chassis, where I can get to
it if it goes agn. From the info I have the V2 uses a internally mtg fuse, not a two-fuse
plug. They may have had them in earlier models. I have a schematic dated 12-16-52 showing
a single fuse, which mine has. Didn't the DX-100 have them?

Tnx Dennis for your input...73 de Bill K4JYS

----- Original Message -----
From: "Dennis DuVall" <duvallddennis at gmail.com>
To: "cwopr" <cwopr at embarqmail.com>
Cc: "boatanchors" <boatanchors at mailman.qth.net>
Sent: Saturday, April 28, 2018 4:01:21 PM
Subject: Re: [Boatanchors] Inrush Current Limiters

What leads you to believe you might have an “inrush” problem with your V2?  Operating V2, Apache and military T-368 (400W out) here for many years with no such problems either in the equipment or on the mains side.
On the fusing question, V2s originally came with a pair of fuses mounted in the power plug.

Dennis DuVall, W7QHO
Glendale, CA

> On Apr 28, 2018, at 10:03 AM, Bill Stewart <cwopr at embarqmail.com> wrote:
>
> I am considering the use of a inrush current limiter for my Viking 2. Anyone using
> one with this or similar xmtr? V2 info says it pulls 375 watts, fully loaded, on AM...
> cw would be less. The ZIM units in ER are rated at 300w. Anyone know of a device
> or ZIM-type unit that would work with the V2? Tnx de Bill K4JYS
>
> PS: Why in the world did they put the fuse inside the thing??
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