Debugging no TX on K2

[Jeff Kinzli]

So I've been debugging as I get time my recently finished K2, and trying
to find out why it's got no output.

Tonight I traced all of the DC voltage points in the troubleshooting
guide, and found two anomolies, both of which are connected to one
another.

On pin 7 of U4, and also pin 1 of U5, I get 4.9V, and the manual
says they should be 0V.

My first thought was a solder bridge, but I see none.

U4 is where there's a mod on the bottom side of the board. My thought now
is that while adding that mod, I overheated U4 and opened up a path
to pin 7 of 5V.

Does that sound possible/reasonable/likely? Would that also cause my
"no output" problem? These chips appear to be in the PLL circuit, so it seems
if these were fried, I'd have frequency/VFO problems, yes?

Since these two pins connect to each other, and nothing else, I don't see
any other way for 5V to get in there.

Or, am I chasing another ghost? :)

Thanks for any ideas guys, you have all been very helpful and I really
appreciate it.

Jeff
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[Charles Pitts]

Jeff,

I also measure 4.89vdc at these pins so that is OK.  I haven't looked to see
why yet.

Have you built the RF probe and traced the transmitter signals as outlined
starting on page 12 of Appendix E of the owner's manual?  If so what were
your findings?

73,
Charles N3EJS

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jeff Kinzli
Sent: Friday, February 02, 2007 11:59 PM
To: [hidden email]
Subject: [Elecraft] Debugging no TX on K2

So I've been debugging as I get time my recently finished K2, and trying
to find out why it's got no output.

Tonight I traced all of the DC voltage points in the troubleshooting
guide, and found two anomolies, both of which are connected to one
another.

On pin 7 of U4, and also pin 1 of U5, I get 4.9V, and the manual
says they should be 0V.

My first thought was a solder bridge, but I see none.

U4 is where there's a mod on the bottom side of the board. My thought now
is that while adding that mod, I overheated U4 and opened up a path
to pin 7 of 5V.

Does that sound possible/reasonable/likely? Would that also cause my
"no output" problem? These chips appear to be in the PLL circuit, so it
seems
if these were fried, I'd have frequency/VFO problems, yes?

Since these two pins connect to each other, and nothing else, I don't see
any other way for 5V to get in there.

Or, am I chasing another ghost? :)

Thanks for any ideas guys, you have all been very helpful and I really
appreciate it.

Jeff
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[Don Wilhelm-3]

Jeff,

If the VFO moves and you can receive, then the PLL is working - that is not
your problem area.
Jave you assembled that RF Probe yet?  That is the key to doing your
analysis.  Do the checks as outlined in the Transmit Signal Tracing section
of Appendix E in the manual.

73,
Don W3FPR

> -----Original Message-----
>
> So I've been debugging as I get time my recently finished K2, and trying
> to find out why it's got no output.
>
> Tonight I traced all of the DC voltage points in the troubleshooting
> guide, and found two anomolies, both of which are connected to one
> another.
>
> On pin 7 of U4, and also pin 1 of U5, I get 4.9V, and the manual
> says they should be 0V.
>
> My first thought was a solder bridge, but I see none.
>
> U4 is where there's a mod on the bottom side of the board. My thought now
> is that while adding that mod, I overheated U4 and opened up a path
> to pin 7 of 5V.
>
> Does that sound possible/reasonable/likely? Would that also cause my
> "no output" problem? These chips appear to be in the PLL circuit,
> so it seems
> if these were fried, I'd have frequency/VFO problems, yes?
>
> Since these two pins connect to each other, and nothing else, I don't see
> any other way for 5V to get in there.
>
> Or, am I chasing another ghost? :)
>
> Thanks for any ideas guys, you have all been very helpful and I really
> appreciate it.
>
> Jeff
>

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2:28 PM

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