[Elecraft] K1 RF board resistance, voltage, L1

[Morrow, Michael A.]

Mark Fickett wrote:

> I've just finished with building the transmitter portion=20
> of the board, and have run across a resistance check and a=20
> couple voltage checks that are off...
>
> Resistance (p. 45): ground (-) to J8 pin 5 should be=20
> 90-110k, but I'm getting 1.5k.

I'd suggest re-checking the orientation of D15.

> Voltage (p.46): all from ground (-), with about 12.8v in=20
> (the supply is rated 13.2v, but the K1 says it's 12.8).

No problem there.  There'll be about 0.3 vdc drop (exact drop depends on =
D16 junction temperature and current flow) across the reverse polarity =
protection diode D16.  13.2 - 0.8 =3D 12.9.

> U8 pin 1 should be 1.3-1.5, and is 1.05

I'd say no problem, that's close enough.

> U8 pin 8 should be 5.1-5.5, is 5.8

I'd say no problem, that's close enough.

> D11 cathode should be 4.0-4.6, is 0.8

I don't know about that one.  Are you sure you had the positive lead of =
your voltmeter connected to the junction of D11 and D12?

> And finally, a question: if I readjust L1 (for the VFO),=20
> will I need to recalibrate the reciever, or will it just=20
> affect the VFO (and .: the band edges)?

No sweat!  When you did the receiver display calibration, you were =
calibrating the LCD display to take into account variations on the =
various heterodyne crystals RF-X5 and filter X1 through X4.  This cal is =
necessary because the LCD display frequency counter only counts the =
output of the VFO (L1), and not the other oscillators. =20

So, you can adjust L1 turn spacing after the earlier band calibration of =
the LCD display, and still have an accurate LCD display of the receiver =
frequency.  Adjusting L1 will, as you suspect, only alter where the band =
coverage starts and ends.  Squeezing together turns on L1 to make the =
VFO operate at a lower frequency will RAISE the K1 lower and upper band =
ends.  Any L1 adjustment will affect all four bands by the same amount.  =
You need not re-do the band cal procedure.

73,
Mike / KK5F

=20