[Elecraft] Sudden K3 problem

Wed Jan 29 12:27:44 EST 2025

Yes the power supply may indicate 13.8 volts, but what is the voltage at 
the radio?  The radio power cable must be connected direct to the power 
supply terminals.  Press DISP and using VFO B knob scroll to the voltage 
display.  Put the radio in transmit and start increasing power.  If at 
100 watts the display shows a decrease of more than 0.5 volts from the 
RX value, there is a DC distribution problem.  Check connections, fuse 
and etc.

If you by chance are using a DC power distribution strip for the radio, 
PLEASE connect the radio power leads direct to the power supply 
terminals.   DC power strips are only good for light current draw items, 
pilot lights, power meters, etc.  This is regardless of their stated 
current ratings.

With my SS-30M supply and my K3S connected directly to the power supply 
terminals, the radio shows 14.5 volts and 1.15 amps in receive and 14.1 
volts and 15.9 amps at 100 watts output.    This is as it should be.  I 
have the power supply at 14.5 volts for a reason.  Somewhat better 
performance and better efficiency, and this is within the safe operating 
voltage of the radio.

73

Bob, K4TAX

On 1/29/2025 11:00 AM, elecraft-request at mailman.qth.net wrote:
> Message: 5
> Date: Wed, 29 Jan 2025 09:11:02 -0500
> From: "James Beitchman"<jbeitchman at jgbconsult.com>
> To:<Elecraft at mailman.qth.net>
> Subject: [Elecraft] Sudden K3 problem
> Message-ID:<[email protected]>
> Content-Type: text/plain;	charset="us-ascii"
>
> While tuning the K3/100 (S/N 1551 plus upgrades) and antenna coupler
> (external) with the SWR 1:1 and the output power at about 75W, suddenly
> there was a click from the K3 and the error message displayed: ERR 12V, This
> now occurs when the power is increased from zero to about 10W.  At that
> point, the problem occurs, and the power cannot be increased above 10W. The
> power supply voltage is constant at 13.8VDC and does not glitch when the
> error occurs. Thoughts?  Would appreciate help.