[Elecraft] Power supply V drop - was poor CW on K3S

[Charlie T]

Well, if you simply "must" have a fuse, use the type that those monster car blasters use, an AGU (5AG) type.  They are 1½" long and 13/32" in diameter with usually gold plated endcaps.

The holders are up to the task as well,  with low resistance gold plated pressure fit caps, and are typically water proof.  They have hex key set screws for the (BEEEG) wire connection.  
Perfect for under hood or home use with fuses available from 100 mA up to 200 Amp ratings at 32VDC.

I don't think you can find a more efficient fuse & holder for low voltage drop.

73, Charlie k3ICH


-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Fred Jensen
Sent: Saturday, April 25, 2020 2:20 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Power supply V drop - was poor CW on K3S

"glass fuses"?  You want to avoid the in-line cylindrical cartridge fuses, the holders almost always have too much resistance.  Blade-type automotive fuses are much better ... much more contact surface, much more contact pressure, and a wiping action as you insert the fuse.  A drop of DeOxit on the blades as you insert the fuse will also help.  If this is a fixed installation and your power supply has some form of overcurrent protection [e.g. crowbar], there may be no need for any fuses in the power cable.

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 4/25/2020 9:01 AM, Chuck Chandler wrote:
> Here's an update.
>
> I replaced the power cable running from the powerstrip with a 3-foot 
> length with glass fuse holders in each leg.  I also adjusted the power 
> supply to 14.50V at rest.  The K3S now shows 14.2V at rest.  At 100W 
> TX the K3S shows 13.2V, so a 1 volt drop.  Way too much.
>
> The power supply voltage measured at the terminals drops from 14.50 to
> 14.44 for full power TX.  This seems too much, I had read the drop 
> should be no more than 0.01V and this is 0.06V.
>
> So, suspecting the in line fuse holders I made up another cable with 
> dual blade-fuse holders, which was worse.  TX voltage on the K3S 
> display dropped to 12.9V.
>
> I'm suspecting my power supply is to blame - it's a TenTec 963, a 
> re-branded Astron SS-30.  Alternatively, I have another commercial 
> power cable with fuse holders I can cut down and try.
>
> Many thanks for all the help both here on the reflector and the direct 
> emails from several fellows, and to Rich VE3KI for the on-air tests 
> this morning!
>
> 73 de Chuck, WS1L
>

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