My K2 is finished up to testing stage but no Transmit - receives fine all bands ideas?

[Clifford Hynds]

Well I finished the K2 only to find no TX preliminary troubleshooting seems
to suggest the T/R switch D6 and D7 are not getting the control signal from
the control board, Also U9 shows higher voltages ,

Is there anything common that may be wrong, All bands peak fine on receive.

thanks for any ideas. I followed the troubleshooting in the manual and
there is no RF right from the TX mixer buffer stages which suggests it is
not being switched into TX mode.

thanks
73
Cliff VK2CCJ
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[Geoffrey Mackenzie-Kennedy-3]

Cliff,

In Tx mode, is the "8T" voltage at the junction of RFC13, C55 and Q20's gate
8 volts plus - minus a tad?

73,
Geoff
LX2AO


On January 03, 2013 at 8:17 PM, Clifford Hynds wrote:

> Well I finished the K2 only to find no TX preliminary troubleshooting
> seems
> to suggest the T/R switch D6 and D7 are not getting the control signal
> from
> the control board, Also U9 shows higher voltages ,
>
> Is there anything common that may be wrong, All bands peak fine on
> receive.
>
> thanks for any ideas. I followed the troubleshooting in the manual and
> there is no RF right from the TX mixer buffer stages which suggests it is
> not being switched into TX mode.
>
> thanks
> 73
> Cliff VK2CCJ

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[Don Wilhelm-4]

Cliff,

If you have RF From the TX mixer, then the K2 is going into transmit -
U10 is powered from the 8T voltage rail and that only comes on during
transmit.  8R and 8T control everything.

Help me understand your statement that U9 shows higher voltages.  My
guess is that pin 3 stays close to 12 volts.
If that is the case, then your problem is most likely that Q20 is the
problem - it should conduct during TX and if it is working properly it
will reduce the voltage on U9 pin 3 to about 6 volts. Those 2N7000 FETs
are easily damaged by static.

73,
Don W3FPR

On 1/3/2013 2:17 PM, Clifford Hynds wrote:

> Well I finished the K2 only to find no TX preliminary troubleshooting seems
> to suggest the T/R switch D6 and D7 are not getting the control signal from
> the control board, Also U9 shows higher voltages ,
>
> Is there anything common that may be wrong, All bands peak fine on receive.
>
> thanks for any ideas. I followed the troubleshooting in the manual and
> there is no RF right from the TX mixer buffer stages which suggests it is
> not being switched into TX mode.
>
> thanks
> 73
> Cliff VK2CCJ
> ______________________________________________________________
> 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
>

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