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[K2] No power on transmit

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bdenley

[K2] No power on transmit

I have completed the last assembly steps leading to Alignment and Test Part
3 and started the testing. Everything went OK until I keyed the transmitter
(using TUNE) at 2 watts. The most power I can get on the internal power
meter is .5 watts. I do see the current draw rise to about 0.44 amps (from
0.22). Adjusting L1,L2 have no effect so there must be a problem in the RF
circuit somewhere. The receiver stil works fine. I looked at T1-T4 but I
don't see anything wrong with the windings. Anyone know what the most
probable causes are to start my troubleshooting phase? BTW I used a 50 ohm
dummy load rated at 50 watts. I will admit that installing T4 links was
extremely difficult due to the closeness of other components.
Thanks
Brian Denley
http://home.comcast.net/~b.denley/index.html

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Don Wilhelm-4

Re: [K2] No power on transmit

Brian,

I think you are in for some Transmit Signal Tracing. If you do not have
a 'scope with a 10X probe or an RF Probe already, build up the RF Probe
included with your K2 kit.
Then turn to Appendix E in the manual and follow the procedure for
Transmit Signal Tracing.
Note that the steps on page 14, the "expected" values are shown for a
properly working K2 at 5 watts. The RF Voltages that you should see
will be higher - up to the point of the failing stage where it will drop
lower. You are looking for that first point where the RF voltage is
lower than the expected value.

73,
Don W3FPR

Brian Denley wrote:

> I have completed the last assembly steps leading to Alignment and Test Part
> 3 and started the testing. Everything went OK until I keyed the transmitter
> (using TUNE) at 2 watts. The most power I can get on the internal power
> meter is .5 watts. I do see the current draw rise to about 0.44 amps (from
> 0.22). Adjusting L1,L2 have no effect so there must be a problem in the RF
> circuit somewhere. The receiver stil works fine. I looked at T1-T4 but I
> don't see anything wrong with the windings. Anyone know what the most
> probable causes are to start my troubleshooting phase? BTW I used a 50 ohm
> dummy load rated at 50 watts. I will admit that installing T4 links was
> extremely difficult due to the closeness of other components.
> Thanks
> Brian Denley
> http://home.comcast.net/~b.denley/index.html
>
> ______________________________________________________________
> 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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Help: http://mailman.qth.net/mmfaq.htm
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Please help support this email list: http://www.qsl.net/donate.html

bdenley

Re: [K2] No power on transmit

Don:
Thanks for the advice. I do have a Tek 2225 with 10x probes so I will start
with that. I wasn't aware that they would be acceptable as RF probes. I
might just start on page 10 and go through everything.
Thanks again for the help!
Brian
http://home.comcast.net/~b.denley/index.html

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Brian Denley" <[hidden email]>
Cc: "Elecraft Reflector" <[hidden email]>
Sent: Saturday, August 21, 2010 8:41 AM
Subject: Re: [Elecraft] [K2] No power on transmit

> Brian,
>
> I think you are in for some Transmit Signal Tracing. If you do not have a
> 'scope with a 10X probe or an RF Probe already, build up the RF Probe
> included with your K2 kit.
> Then turn to Appendix E in the manual and follow the procedure for
> Transmit Signal Tracing.
> Note that the steps on page 14, the "expected" values are shown for a
> properly working K2 at 5 watts. The RF Voltages that you should see will
> be higher - up to the point of the failing stage where it will drop lower.
> You are looking for that first point where the RF voltage is lower than
> the expected value.
>
> 73,
> Don W3FPR
>
> Brian Denley wrote:
>> I have completed the last assembly steps leading to Alignment and Test
>> Part 3 and started the testing. Everything went OK until I keyed the
>> transmitter (using TUNE) at 2 watts. The most power I can get on the
>> internal power meter is .5 watts. I do see the current draw rise to
>> about 0.44 amps (from 0.22). Adjusting L1,L2 have no effect so there
>> must be a problem in the RF circuit somewhere. The receiver stil works
>> fine. I looked at T1-T4 but I don't see anything wrong with the
>> windings. Anyone know what the most probable causes are to start my
>> troubleshooting phase? BTW I used a 50 ohm dummy load rated at 50 watts.
>> I will admit that installing T4 links was extremely difficult due to the
>> closeness of other components.
>> Thanks
>> Brian Denley
>> http://home.comcast.net/~b.denley/index.html
>>
>> ______________________________________________________________
>> 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
>>
>>

Don Wilhelm-4

Re: [K2] No power on transmit

Certainly, a 'scope will act as an amplitude measuring device for RF -
up to a frequency limit. The frequency rating for the 'scope as well as
the probe must be taken into consideration. If both the probe and the
'scope are rated for 100 MHz, then they are quite usable up through 20
MHz and possibly even up to 30 MHz. The frequency rating of the 'scope
and probe is where the response is 3 dB down, so if the frequency rating
is 100 MHz, you will see only half the actual amplitude at 100 MHz.

Since the values listed are for RMS as read by an RF probe, multiply the
"expected" values by 2.8 (use 3 for quick multiplication) to obtain the
peak to peak values seen on the 'scope.

73,
Don W3FPR

Brian Denley wrote:

> Don:
> Thanks for the advice. I do have a Tek 2225 with 10x probes so I will start
> with that. I wasn't aware that they would be acceptable as RF probes. I
> might just start on page 10 and go through everything.
> Thanks again for the help!
> Brian
> http://home.comcast.net/~b.denley/index.html
>
>
>