[Elecraft] K2 #2740 13 Khz Off Frequency

Sun Aug 18 22:34:01 2002

Well here are more details on my problem with the K2. (VFO reads 13KHz
higher that actual frequency and images at 1 KHz below)

Measured the DC voltage at pin 1 of U6 on the RF board.

It DOES move smoothly except for 1 instance....

When I use the CAL FCTR and measure TP-3, the frequency changes between
12.087.00 MHz (pin 1 measures 1.6 volts) and 12082.40 (pin 1 measures .44
volts).

The anomaly comes when the VCO frequency reads 12.102.39 MHz, the voltage is
7.17 volts! This reading occurs only within about a 200 Hz change of the VFO
knob! ALSO, when the VCO voltage is 7.17 volts and the VCO frequency is
12.102.39 MHz, the K2 is within about 1 KHz of being on frequency.

I have checked all of the components for the proper marked value around the
VCO circuit. All check out fine. I have also checked the Vcc on both U5 and
U6.

If I had to guess, I would say that the microprocessor is telling the A/D
converter to work this way. Small possibility that U5 is defective.

I have also checked for solder bridges on the control board and have found
none. (This is not my first kit !! ) I have been soldering circuit boards
for 27+ years. ( I do however make mistakes :)  )

What do you think ??

73 and thanks
Jim W7RY

----- Original Message -----
From: "Jim W7RY" <[email protected]>
To: <[email protected]>
Sent: Friday, August 16, 2002 7:21 PM
Subject: [Elecraft] K2 #2740 13 Khz Off Frequency

> Well... I have # 2740 running as a 40 meter receiver... But, it receives
> exactly 13Khz off frequency (VFO reads high).
>
> There is another peculiar thing.... at 11.5 KHz above the injected
> frequency, there is a "birdie". The birdie moves much faster than the
> fundamental at +13 KHz above.
>
> I have verified that all of the crystals AS SUPPLIED are installed in the
> correct locations...
>
> I have also verified that the 4.00 MHz reference is within 1 or 2 Hz.
>
> All of the checks and alignments that are shown in "Alignment and Test
Part
> II" starting on page 57 are correct and line up perfectly.
>
> The parts list spells out  X1 and X2 to be a 12.069 MHz. My kit contained
> crystals that are marked  12.09-S.
> In addition, X5 through X11 are marked 4.9136-S.
>
>
> The receiver works great! Very sensitive.
> The signal I am injecting is at a level of -105dBm. (Not overloading the
> receiver).
>
> Any ideas ?
>
> Thanks and 73
> Jim W7RY
>
>
>
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