K2/100 - voltage drop across DC cable

[ON4WIX]

Hi all

This afternoon, just out of curiosity, I put a DVM across the DC input terminals of my K2/100. The power supply I'm using is a Kenwood PS-53 and the cable between the PS and my K2 is the "Elecraft issue" cable.
Upon hitting the "tune" button (with the K2 connected to a known good dummy load) I noticed that the voltage across the input dropped to 12V. Getting curious I rotated the "Power" knob so the tune mode would go to full power out. Much to my surprise the voltage across the K2's input terminals dropped to a meagre 9,2 volts when the K2 was putting out 105 watts. I ran the same tests again, this time with the DVM connected across the PS's terminals. As you probably can guess this voltage was rock solid (around 14 volts).

So I guess I've got myself a suspect DC feed cable which dissipates a *lot* of power across the 5V voltage drop when running the rig at full throttle. I need to check the Powerpole connectors and the fuse holder. Knowing that several of you have run into the same problem before, are there any telltale signs of bad connections? Sometimes the simple things are the hardest to spot... I know I could try reflowing the solder on all connections but maybe some time an be saved...
FWIW, DC resistance across the red lead is 0.2 ohms, DC resistance across the black lead is slightly less at 0.1 ohms when measured out of circuit.

Thanks in advance for any suggestions.

CU this weekend in the UBA CW DX contest

Glenn ON4WIX/OR4W

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[Ron D'Eau Claire-2]

Since you're using Elecraft-issued cable and the Anderson connectors, I'd
start by checking the in-line fuse. The pressure contacts can oxidize a bit
and build up resistance. Also, check the fuse itself (I do that by trying a
new one). Sometimes the fuse will start to fail, developing cracks in the
conductor, often at one end where it's connected to the end cap and you
can't see it.

For comparison, at 18 amps total current, my K2/100 shows 12.0 volts even on
the LCD display at 105 watts; 13.5 VDC key up from a nominal 13.8 VDC Astron
supply.

Ron AC7AC

-----Original Message-----

Hi all

This afternoon, just out of curiosity, I put a DVM across the DC input
terminals of my K2/100. The power supply I'm using is a Kenwood PS-53 and
the cable between the PS and my K2 is the "Elecraft issue" cable. Upon
hitting the "tune" button (with the K2 connected to a known good dummy load)
I noticed that the voltage across the input dropped to 12V. Getting curious
I rotated the "Power" knob so the tune mode would go to full power out. Much
to my surprise the voltage across the K2's input terminals dropped to a
meagre 9,2 volts when the K2 was putting out 105 watts. I ran the same tests
again, this time with the DVM connected across the PS's terminals. As you
probably can guess this voltage was rock solid (around 14 volts).

So I guess I've got myself a suspect DC feed cable which dissipates a *lot*
of power across the 5V voltage drop when running the rig at full throttle. I
need to check the Powerpole connectors and the fuse holder. Knowing that
several of you have run into the same problem before, are there any telltale
signs of bad connections? Sometimes the simple things are the hardest to
spot... I know I could try reflowing the solder on all connections but maybe
some time an be saved... FWIW, DC resistance across the red lead is 0.2
ohms, DC resistance across the black lead is slightly less at 0.1 ohms when
measured out of circuit.

Thanks in advance for any suggestions.

CU this weekend in the UBA CW DX contest

Glenn ON4WIX/OR4W

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[ON4WIX]

Wow, that was quick!

Ron, you were right on the money: oxidized contacts.
So there is no need to reflow any soldered connections here, just cleaning
some contacts cured the problem. Running full power (now up to 115 watts)
now yields a voltage of 13.7 volts across the K2's input terminals. Voltage
at RX is 14.2 volts.
Thanks also to Tom N0SS for the comparison with larger gauge cable.

This reflector really adds to the "Elecraft experience".

73 and thanks again!

Glenn ON4WIX/OR4W
K2/100 s/n 5361

----- Original Message -----
From: "Ron D'Eau Claire" <[hidden email]>
To: "'ON4WIX'" <[hidden email]>; <[hidden email]>
Sent: Thursday, February 22, 2007 7:09 PM
Subject: RE: [Elecraft] K2/100 - voltage drop across DC cable

> Since you're using Elecraft-issued cable and the Anderson connectors, I'd
> start by checking the in-line fuse. The pressure contacts can oxidize a
> bit
> and build up resistance. Also, check the fuse itself (I do that by trying
> a
> new one). Sometimes the fuse will start to fail, developing cracks in the
> conductor, often at one end where it's connected to the end cap and you
> can't see it.
>
> For comparison, at 18 amps total current, my K2/100 shows 12.0 volts even
> on
> the LCD display at 105 watts; 13.5 VDC key up from a nominal 13.8 VDC
> Astron
> supply.
>
> Ron AC7AC
>
> -----Original Message-----
>
> Hi all
>
> This afternoon, just out of curiosity, I put a DVM across the DC input
> terminals of my K2/100. The power supply I'm using is a Kenwood PS-53 and
> the cable between the PS and my K2 is the "Elecraft issue" cable. Upon
> hitting the "tune" button (with the K2 connected to a known good dummy
> load)
> I noticed that the voltage across the input dropped to 12V. Getting
> curious
> I rotated the "Power" knob so the tune mode would go to full power out.
> Much
> to my surprise the voltage across the K2's input terminals dropped to a
> meagre 9,2 volts when the K2 was putting out 105 watts. I ran the same
> tests
> again, this time with the DVM connected across the PS's terminals. As you
> probably can guess this voltage was rock solid (around 14 volts).
>
> So I guess I've got myself a suspect DC feed cable which dissipates a
> *lot*
> of power across the 5V voltage drop when running the rig at full throttle.
> I
> need to check the Powerpole connectors and the fuse holder. Knowing that
> several of you have run into the same problem before, are there any
> telltale
> signs of bad connections? Sometimes the simple things are the hardest to
> spot... I know I could try reflowing the solder on all connections but
> maybe
> some time an be saved... FWIW, DC resistance across the red lead is 0.2
> ohms, DC resistance across the black lead is slightly less at 0.1 ohms
> when
> measured out of circuit.
>
> Thanks in advance for any suggestions.
>
> CU this weekend in the UBA CW DX contest
>
> Glenn ON4WIX/OR4W
>
>
>
>
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.441 / Virus Database: 268.18.3/697 - Release Date: 22/02/2007
> 11:55
>

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[Don Wilhelm-3]

Glenn,

If you continue to have problems with the fuse contacts oxidizing, consider
replacing the fuseholder with ann automotive ATO type in-line fuse.  Those
ATO fuseholders generally have a tighter 'grip' on the fuse legs which
creats a lower resistance than the spring loaded end contact type.

73,
Don W3FPR

> -----Original Message-----
>
> Ron, you were right on the money: oxidized contacts.
> So there is no need to reflow any soldered connections here, just
> cleaning
> some contacts cured the problem. Running full power (now up to 115 watts)
> now yields a voltage of 13.7 volts across the K2's input
> terminals. Voltage
> at RX is 14.2 volts.
> Thanks also to Tom N0SS for the comparison with larger gauge cable.
>
> This reflector really adds to the "Elecraft experience".
>
> 73 and thanks again!
>
> Glenn ON4WIX/OR4W
> K2/100 s/n 5361
>

--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.441 / Virus Database: 268.18.3/697 - Release Date: 2/22/2007
11:55 AM

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