[Elecraft] K3 Stops Transmitting (solved)

[George Thornton]

I have written about this before.  I have had similar problems at Field Day, and some friends of mine have also had issues while in mobile contest use.

From what I can tell, the K3 can be very sensitive to power voltage levels.  If there is any issue with the power supply itself, or if the cables between the power supply are too long or not of sufficient gauge, power levels can drop at the K3 and can lead to problems including no or limited transmit power.

As an example, I have an Astron power supply mediated through a PWRgate device and a separate power distribution panel.  When I route my K3 power this way, I can see a drop of as much as one volt or more of input voltage according to the K3's internal voltage meter when I transmit.

On the other hand, using a short run of thick gauge wire direct from the PS to the K3, the voltage drop is only .1 or.2 volts.

My friend had problems in mobile use in a contest going from the vehicle generator (motor on) to car battery.  He ended up installing a voltage booster device to get solid performance.

When this happens I was able to restore function by reinstalling firmware and recalibrating the transmit power.



From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Charlie T, K3ICH
Sent: Monday, March 20, 2017 5:13 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3 Stops Transmitting (solved)

Well, at least you did (a logical) SOMETHING which in all probability, fixed
the intermittent.
The hardest problems to solve are those where the fault just disappears but
you did NOTHING to fix it.

Fault...open lid....close lid...problem fixed = Yuge question mark!

Thanks especially for sharing your "fix".
It may save a few of us a lot of hair-pulling and/or a trip back to
Elecraft.

It is very frustrating to hear of a problem, and never find out what fixed,
or didn't fix it.

73, Charlie k3ICH



-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Dennis
Sent: Monday, March 20, 2017 7:34 AM
To: Reflector Elecraft <elecraft at mailman.qth.net><mailto:elecraft at mailman.qth.net%3e>
Subject: [Elecraft] K3 Stops Transmitting (solved)

A couple of weeks ago I posted that my K3 suddenly stopped transmitting
during ARRL CW.
The PTT would enable, it was not in TEST mode, the CW monitor would sound,
but no output.
Pushing the TUNE button would result in "0 watts" showing on the display.
The problem persisted after I power cycled the radio, plugged/unplugged the
DC source, tried various control changes, and a soft "drop" test. Through
all of this, the Rx worked just fine. Nothing restored the radio
transmitting ability. So, I swapped it out and continued the contest.

When I got home, I hooked the radio up and it transmitted just fine.
Something happened that
stopped the radio from transmitting, but now it worked fine. So I posted my
experiences here and asked for suggestions.

A number suggested the DC power supply cable. My experiences at the site
suggested that wasn't the culprit. A number suggested that I had somehow
put the radio into "TEST" mode, but I was sure I had not. I even toggled
into and out of "TEST" mode several times, but that didn't solve the
problem. Several suggested that a voltage had been applied to the Inhibit
pin of the ACC15 connector, but there was nothing plugged into the ACC15
socket. Two suggestions seemed most plausible: that one of the coax cables
from the new synthesizer to the other boards was intermittent, or that the
Sub Rx plugs was intermittent.

Once I had a place to look, I opened the radio and did the following:
1. Took a pair of long nose pliers and GENTLY rotated and firmly seated each
coaxial cable connector connecting the synthesizer board to the rest of the
radio.
All seemed to be secure
and in tight, but they were all rotated just a little.
2. Checked the seating of the Sub Rx into its connectors. The back
connector was not fully
seated- I'd say it was about 80% seated, but there is a little play in the
connector. It is now fully seated.

Since then, I've operated the radio about 30 hours in contesting. The no
transmit problem has not come back. Did I fix it? The problem had never
happened before, I don't have a clear problem that was solved, but it has
made it 30 hours now without a problem. At least for now, I feel the
problem has been solved.

Dennis W1UE
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