[Elecraft] K3 Sub Rx RF Gain issue and TX sticking

[Guy Olinger K2AV]

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 <elecraft at mailman.qth.net>
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
>
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