fun k2 debugging

[Robert Greenwalt-2]

So I have a K2 all put together.  I thought it was receiving fine - I didn't
try transmitting as I shamefully don't have CW down yet.  I got the ssb kit
and put it together and it didn't transmit.  I stripped it out (jumpers back
in place at W2, W3 and C167 is back in) and tried testing cw transmit and
found a problem, but didn't fix it.  So now I'm testing the voltages and
finding some odd numbers.  Perhaps they've been seen before:

Q18 S is giving 4.9V instead of the suggested 2-3V
Q18 D is giving 8V instead of 6.3
U1 pin9 and 10 give 0V
U4 pin3 gives 2.4V instead of 0
U4 pin7 gives 5V instead of 0
U4 pin13 gives 0V instead of 4
U4 pin15 gives 2.5V instead of 5
U5 pin1 is 5 instead of 0
U5 pin2 is 0 instead of 5
U5 pin4 is 0 instead of 5

Suggestions on where to start?

Thanks
K6RJG
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[Don Wilhelm-4]

I would start with the voltage at the source of Q18.  Actually the high
voltage is just the indicator of the problem, Q18 is not faulty, the
resistance between the source and ground is the problem.  You should
measure close to 270 ohms, but I would think you will find it higher
than that.  Check R20 and RFC11 - particularly, check the tinning and
soldering of RFC11.

Did you have good results when you checked the PLL Range earlier during
the construction?  With the high DC voltage on the source of Q18, I
would think not.  What kind of voltages did you find at the left end of
R30 when you checked those - especially when tuned to 4000 kHz and when
tuned to 7000 kHz.  Was CAL PLL successful?

Take the rest of those voltage measurement points one at a time.  U4
pins 3, 8, 9, 10, 11, 14 and 15 have nothing connected to them, so don't
be concerned about the actual voltage on those.

What works and what does not.  Both elements are important to homing in
on your problem.
Use the schematic and follow the signal paths.

73,
Don W3FPR

Robert Greenwalt wrote:

> So I have a K2 all put together.  I thought it was receiving fine - I didn't
> try transmitting as I shamefully don't have CW down yet.  I got the ssb kit
> and put it together and it didn't transmit.  I stripped it out (jumpers back
> in place at W2, W3 and C167 is back in) and tried testing cw transmit and
> found a problem, but didn't fix it.  So now I'm testing the voltages and
> finding some odd numbers.  Perhaps they've been seen before:
>
> Q18 S is giving 4.9V instead of the suggested 2-3V
> Q18 D is giving 8V instead of 6.3
> U1 pin9 and 10 give 0V
> U4 pin3 gives 2.4V instead of 0
> U4 pin7 gives 5V instead of 0
> U4 pin13 gives 0V instead of 4
> U4 pin15 gives 2.5V instead of 5
> U5 pin1 is 5 instead of 0
> U5 pin2 is 0 instead of 5
> U5 pin4 is 0 instead of 5
>
> Suggestions on where to start?
>
> Thanks
> K6RJG
> ______________________________________________________________
> 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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