Strange K3 microphone /PTT fault

[john petters]

Greetings folks,
I'm puzzled. my 7 year old K3 did two strange things this evening.

During a CW QSO on 21MHz, it appeared not to go back into receive and
required power off and on to operate. The QSO finished.

Then, in the middle of a USB QSO on 5MHz - mid transmission, it went
back to receive and the PTT would not go back to TX, nor did the Vox work.

I can operate the PTT on the back socket of the rig, and by grounding
pin 2 on the 8 pin mic connector.

On measuring the pins 7 & 8, which should go to ground, these seem to be
floating and not grounded.

I've just looked at the circuit and it shows these pins going to ground.

Any suggestions?

73
--
John Petters
Amateur Radio Station G3YPZ
www.traditional-jazz.com
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[Matt Zilmer-3]

Hi John,

If it were me, I'd reseat the front panel assembly to the RF board.  I
had to do this many moons ago (like 8 years...) one time and it fixed
the problem.  The only guess I have for what's wrong is some minor
corrosion on on some of the front panel pins.

John, I hope this does it for you.  Can't think of anything else.

73!
matt
W6NIA

On Fri, 2 Oct 2015 00:19:40 +0100, you wrote:

>Greetings folks,
>I'm puzzled. my 7 year old K3 did two strange things this evening.
>
>During a CW QSO on 21MHz, it appeared not to go back into receive and
>required power off and on to operate. The QSO finished.
>
>Then, in the middle of a USB QSO on 5MHz - mid transmission, it went
>back to receive and the PTT would not go back to TX, nor did the Vox work.
>
>I can operate the PTT on the back socket of the rig, and by grounding
>pin 2 on the 8 pin mic connector.
>
>On measuring the pins 7 & 8, which should go to ground, these seem to be
>floating and not grounded.
>
>I've just looked at the circuit and it shows these pins going to ground.
>
>Any suggestions?
>
>73

Matt Zilmer, W6NIA
--
"Always store beer in a dark place."  -R. Heinlein

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[Lyle Johnson]

If Pins 7 and 8 are connected together (verify with ohm meter) but not
connected to the mic jack shell, you may wish to remove the front panel
assembly and look just above the Mic Jack at a component labeled "L4".  
It should be a short.  If it is broken, or other than a short, replace
it with a short length of wire to jumper it, or otherwise jumper pins 7
and 8 to ground nearby.

K3 product produced starting sometime in 2012 did not have this
component; earlier ones did and required the jumper.

73,

Lyle KK7P

...
I can operate the PTT on the back socket of the rig, and by grounding
pin 2 on the 8 pin mic connector.

On measuring the pins 7 & 8, which should go to ground, these seem to be
floating and not grounded.

I've just looked at the circuit and it shows these pins going to ground.

Any suggestions?

______________________________________________________________
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