[Elecraft] My K2 is finished up to testing stage but no Transmit - receives fine all bands ideas? Now TX sought of?

[Clifford Hynds]

Ok fixed the no transmit problem Don,

Found a small solder bridge from the 8T Q1 Collector to ground at the mic
header.

So now it transmits but after aligning get low power about 5W on 80 40 30
and not much at all on the other bands.

So back to troubleshooting again. Disappointing. Dc Voltages around the PA
seems ok, I did notice the ALC voltage at U8 seems a bit high at 2.8 -2.9V

The RF troubleshooting in the manual shows similar readings but differfent
as i am using a Fluke RF probe.
Might be time to dig out the scope.

So I think I am close but not there yet.

73 Cliff VK2CCJ


On Sat, Jan 5, 2013 at 6:23 AM, Clifford Hynds <vk2ccj at gmail.com> wrote:

> Thanks Don,
>
> Will get back to it but working the weekend may be tonight I'll take some
> more readings . One thing when I hit the tune button it shows 0.5W but no
> actual output ? You may be right in that Q20 is fried, I did use a
> wriststrap etc..
>
> Hope it is something simple,
>
> 73
> Cliff VK2CCJ
>
>
> On Fri, Jan 4, 2013 at 8:25 AM, Don Wilhelm <w3fpr at embarqmail.com> wrote:
>
>> 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
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>