K2 no power and low receive audio

[rhapak]

My K2 has the SSB option as well as the Noise Blanker.
The radio functions normally for a period of time then the radio has no output power and the receive audio is noticeably lower. There is no output power on SSB or CW, on any bands.
If I shut it down for some time and then turn it back on, it functions normally again for a while, which leads me to believe my problem occurs when the radio heats up and returns to normal when it cools down.

Before I start blindly troubleshooting I would like to have a plan.
Any suggestions on what circuitry would be involved to look at first??

Any help would be appreciated!
Rod
VA3ZVT

[Don Wilhelm-4]

Rod,

Just in case it is the KSB2. board that has the problem, get that out of
the way - remove  the board and bend pieces of #24 wire to fit between
pins 1 and 3 of both J9 and J10.  That will allow the K2 to receive with
the KSB2 removed.  To enable transmit either re-install C167 or get a
.001 uF capacitor with long leads and stick the leads into J11 pins 7
and 12.

I would think chasing the transmit problem would be easier than the
receive path - and it may be the same problem source.  Turn the manual
to the back and do the steps called for in the Transmit Signal Tracing
portion.

If this is a new build that has never worked before, you may have
multiple problems, but if this K2 was working properly before, there is
likely only one problem.

A problem that changes behavior over heat and time is usually due to a
poor solder connection.  Once you find the failing stage, re-flow the
soldering wiht a hot (750 degF) iron adding just a touch of solder so
there is new flux on the connection.  If your colder connections look
more like balls than a "mountain with concave sides", then your solder
connections did not receive enough heat for the solder to flow.
You can see figures depicting good and bad solder connections in the
Elecraft Soldering Tutorial.

73,
Don W3FPR

On 7/23/2012 2:31 PM, rhapak wrote:

> My K2 has the SSB option as well as the Noise Blanker.
> The radio functions normally for a period of time then the radio has no
> output power and the receive audio is noticeably lower. There is no output
> power on SSB or CW, on any bands.
> If I shut it down for some time and then turn it back on, it functions
> normally again for a while, which leads me to believe my problem occurs when
> the radio heats up and returns to normal when it cools down.
>
> Before I start blindly troubleshooting I would like to have a plan.
> Any suggestions on what circuitry would be involved to look at first??
>
> Any help would be appreciated!
> Rod
> VA3ZVT
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/K2-no-power-and-low-receive-audio-tp7559696.html
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