RE: K2 BFO Test Problems

Posted by Don Wilhelm-3 on Feb 19, 2007; 5:17am
URL: http://elecraft.85.s1.nabble.com/K2-BFO-Test-Problems-tp443892p443894.html

Craig,

The problem is most likely in one of the following  areas:
1) The L33 inductor
2) The varactors
3) The crystals themselves.

The very most likely problem is a poor solder connection, and the second
most likely is misplaced components.
The DC voltages look to be within reason, and it is probably not the fault
of U11.

We can get to precise measuremnts tomorrow, it is getting late here today.

73,
Don W3FPR

> -----Original Message-----
>
> Hello again,
>
> I've continued my troubleshooting efforts but the problem persists.
> I had reflowed all connections except those of X3, so I removed L33
> and R116 to do so.  Everything appears to be well connected and I
> don't see any shorts.
>
> I checked the DC voltages on U11 using the internal probe and have
> the following values:
>
> Pin 1: 1.4
> Pin 2: 1.4
> Pin 3: 0.0
> Pin 4: 4.8
> Pin 5: 4.8
> Pin 6: 5.6
> Pin 7: 5.0
> Pin 8: 6.0
>
> I used the RF probe to check the voltages with the following results:
>
> U11, pin 6: 0.74
> TP2: 0.024
>
> The DC voltages for U11 pins 6 and 7 are a bit low and the RF probe
> values are on the edges.  Is it possible that U11 is bad?
>
> 73,
>
> Craig
>
>
> On 18 Feb, 2007, at 10:46, Craig Young wrote:
>
> > Hello to the group.
> >
> > I am currently working through the Alignment and Test, Part II and
> > have run into the following issue.  When I perform the BFO Test, I
> > don't get the proper range.  The set of values I get are:
> >
> > BFO High Freq.: 4917.31 kHz
> > BFO Low Freq.:  4916.97 kHz
> > Range: 0.34 kHz
> >
> > The documentation states that if the BFO range is less than 3.6
> > kHz, the varactor diodes (D37 and D38) or the crystals (X3 and X4)
> > may be incorrect.  However, I've verified them and they are
> > correct.  I've also gone around looking for bad soldering (cold
> > joints or bridges) and didn't see anything obvious.  I've checked
> > the resistors and capacitors in the BFO section and they appear to
> > be correct.
> >
> > Does anyone have any ideas of where I should look next?
> >
> > 73,
> >
> > Craig AC6NN
> >
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