Posted by
Ron D'Eau Claire-2 on
Feb 22, 2007; 6:09pm
URL: http://elecraft.85.s1.nabble.com/K2-100-voltage-drop-across-DC-cable-tp444116p444117.html
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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