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Re: K-1 VFO range jump

Posted by Mike Morrow-3 on Jun 24, 2012; 11:48pm
URL: http://elecraft.85.s1.nabble.com/K-1-VFO-range-jump-tp7558063p7558070.html

> My K-1 quit (no TX, no RX)...
>
> Originally set up for 7.000-@7.060; 14.000-@14.060.

That's a little unusual...with the standard narrow VFO span
option for RF-C2 of 82 pf the K1 will typically tune from
about xx.000 to xx.085 or so.

> I removed and replaced the filter board.  RX, TX fine
> except the range is now 14.047.3 - 14.075.1 and
> 7.053.6 - 7.081.3.

Was *anything* shown on the LCD back when the K1 was not
working at all?

> Spread the turns of L1 and could get to go as low as
> 7.0361 and as high as 7.0640.  
>
> I'm reluctant to snip off a turn from L1 since it worked
> fine before with the current number of turns.

Absolutely do NOT do anything to L1.  You did not need to
adjust turn spacing...but you will after you fix the
problem to get it back to where it should be.

Find the two terminals of the VFO pot that have FP-R19 100k soldered to them.

Rotate the VFO pot to full CCW position.

Measure the voltage from each of these terminals to
ground (the screw anchor blocks for the cover work well).

You *should* find 5.9 to 6.0 volts at each point.

Next, turn on RIT and report how much the LCD frequency
changes from full CCW to full CW.  This should be about
8 kHz (+/- 4 kHz around center frequency).

I suspect that there may be a problem with the 6V VFO
regulator RF-U6 (ZR78L06C) and what you observe above
can help determine that.

The actual output frequency of your VFO should be about
3090 kHz (VFO pot full CCW) to 3005 kHz (VFO pot full CW).

73,
Mike / KK5F
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