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K3 Sub Rx RF Gain issue and TX sticking

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K3 Sub Rx RF Gain issue and TX sticking

The RF Gain control on the Sub RX acts weird. It will seem deaf until 3
o'clock on the dial. Once past 3, the gain jumps up and then is linear
if you turn it down. This pattern will repeat if you turn off the Sub
Rx and turn it back on again. The main RX Rf Gain control is smooth and
linear all through the dial range. I have done the RX calibration
routine on both receivers.

During Field Day, if I hit the Esc Key or the paddle to interrupt a CQ
(N1MM+) , my external keyer (MKUSB) would stop keying but the rig would
stay in transmit mode. Tapping the XMT button would put the rig back to
RX mode.

Ideas?

--
Buck
k4ia K3 #101
Honor Roll 333
8B DXCC

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Guy Olinger K2AV

Re: K3 Sub Rx RF Gain issue and TX sticking

Hi Buck,

While the RF gain control results in digital advice being sent to the K3's
CPU, it is not an encoder like some other controls on the front panel. This
will not be a firmware issue.

The RF and AF gain controls are dual potentiometers. A standard voltage is
placed across the pot (the two ends of the resistance stripe) and the wiper
voltage is connected to an analog-to-digital converter. The digital output
is sent over a multiplexed digital line to the CPU. The trouble you quote
is not likely to go away, because it probably occurs from a cracked
resistance stripe and/or a bent wiper, usually caused by a blow to the
potentiometer knob(s).

You will need to replace the pot, or have it replaced by Elecraft. This is
not one of those eensy-teensy, fly-spec SMT repairs, you can actually see
everything without a magnifying glass. Most people handy at soldering small
electronic parts can do this repair, though it does involve a lot of
disassembly to remove the forward board from the case front panel to expose
everything.

Contact Elecraft for a how-to conversation, a decision, and a replacement
component or an RMA to repair.

73, Guy K2AV

On Thu, Jul 2, 2015 at 2:06 PM, K4ia via Elecraft <[hidden email]>
wrote:

> The RF Gain control on the Sub RX acts weird. It will seem deaf until 3
> o'clock on the dial. Once past 3, the gain jumps up and then is linear if
> you turn it down. This pattern will repeat if you turn off the Sub Rx and
> turn it back on again. The main RX Rf Gain control is smooth and linear
> all through the dial range. I have done the RX calibration routine on
> both receivers.
>
> During Field Day, if I hit the Esc Key or the paddle to interrupt a CQ
> (N1MM+) , my external keyer (MKUSB) would stop keying but the rig would
> stay in transmit mode. Tapping the XMT button would put the rig back to RX
> mode.
>
> Ideas?
>
> --
> Buck
> k4ia K3 #101
> Honor Roll 333
> 8B DXCC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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Joe Subich, W4TV-4

Re: K3 Sub Rx RF Gain issue and TX sticking

In reply to this post by Elecraft mailing list

On 2015-07-02 2:06 PM, K4ia via Elecraft wrote:
> The RF Gain control on the Sub RX acts weird. It will seem deaf
> until 3 o'clock on the dial.

Perform an RF Gain calibration using an XG2/XG3 and the automated
procedure in the K3 Utility software.

> During Field Day, if I hit the Esc Key or the paddle to interrupt a
> CQ (N1MM+) , my external keyer (MKUSB) would stop keying but the rig
> would stay in transmit mode.

Make sure you *do not* enable *any* of the "PTT via Radio Command"
option in the N1MM+ radio port dialogs. Limit PTT to hardware (RTS
or Winkey PTT) sources.

73,

... Joe, W4TV

On 2015-07-02 2:06 PM, K4ia via Elecraft wrote:

dmb@lightstream.net

Re: K3 Sub Rx RF Gain issue and TX sticking

In reply to this post by Elecraft mailing list

You can easily check any of the four potentiometers (RF/AF gains) for
discontinuities via a utility available from the K3's CONFIG menu:

First, turn "TECH MD" ON

Then, find the "SW TEST" option, rotate the VFO-A knob until you see "Scn
Adc" on the display.

Then, while observing the VFO-B area of the display, rotate your suspect
RF gain control and you'll see the individual steps, which should change
from 002 (fully CCW) through 240 (full CW). Turn it very slowly so that
you can see individual steps, looking for any discontinuities.

73, Dale
WA8SRA

> The RF Gain control on the Sub RX acts weird. It will seem deaf until 3
> o'clock on the dial. Once past 3, the gain jumps up and then is linear
> if you turn it down. This pattern will repeat if you turn off the Sub
> Rx and turn it back on again. The main RX Rf Gain control is smooth and
> linear all through the dial range. I have done the RX calibration
> routine on both receivers.
>
> During Field Day, if I hit the Esc Key or the paddle to interrupt a CQ
> (N1MM+) , my external keyer (MKUSB) would stop keying but the rig would
> stay in transmit mode. Tapping the XMT button would put the rig back to
> RX mode.
>
> Ideas?
>
> --
> Buck
> k4ia K3 #101
> Honor Roll 333
> 8B DXCC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>