[Elecraft] K3 won't unkey properly: Rear panel PTT

[Dan Sherwood]

I have discovered an issue with my K3, (ser 5820).

When using my Tigertronics Signalink USB device, the unit keys the rig fine,
but when the interface unkeys, transmission ceases, but red XMIT light stays
on and reception is muted.  Like an indeterminate state.

I did the following:

Updated firmware ­ no difference.

Unplugged Signalink rig cable to r/o a short ­ no difference.

Ran a different digital program on laptop ­ no difference.

The rig is configured to accept audio input from the line in jack on the
rear when placed in DATA-A mode.  In SSB mode it accepts input from either
the front panel or the rear MIC jack depeng on whether I am using a headset
or the boom mic.  PTT is asserted through a foot switch via the front panel
MIC jack.  This keys and UNKEYS normally.

The Signalink assertes PTT through the PTT jack on the rear panel of the K3.
It has an internal relay acting like VOX.

When I use the signalink to key up in data mode, it works OK for a few
cycles, then reverts to the indeterminate state.  Rig will not receive until
I tap one of the keys mentioned below.

To rule out RF feedback issues, I keyed the signalink in SSB mode, so
line-in not selected,  Rig keys up but no power made, (signalink audio not
selected).  Problem persists.

Normal CW and SSB using foot switch PTT and either full or semi break in CW
has no issues, even when driving an amp and lots of RF.

CW through FLDIGI uses CAT keyup and release.  No issues there.  PSK uses
PTT asserted through rear panel.  Issue seems with rear panel PTT only.

Now here¹s the really strange thing:  When in this indeterminate muted
state, if I tap band up or down, mode up or down, AFX, XIT, or RIT keys, the
unit goes back to normal receive.  That initial tap DOES NOT perform the
key¹s design function.  This is like a computer keyboard when a screensaver
is running ­ the first keypress is ³swallowed² to wake up the screen, then
subsequent keypresses work normally.  Any ideas here?

Thanks,

Dan Sherwood W6DAS