VCO Alignment - HOW?

[Fred (FL)]

I've gotten to Alignment & Test, Part II RF Board
build on my K2 # 5422.

I seem to be having problems with "VCO Alignment"
problems:

a. 4 Mhz Oscillator Calibration = gave a reading of
12099.35 - OK it appears.

b. PLL Reference Oscillator Range = 12099.32 high, to
12085.65 low - Range = 13.67khz - seems OK

c. VCO Test:  Frequency counter probe to VCO Test
Point TP1.  I got a frequency counter reading of
8913.18, seemingly stable - and OK.

I'm trying to do VCO Alignment, and adjust Inductor
L30 - to adjust and measure the VCO control voltage
for
proper range.

I'M NOT SURE WHAT THE RELATIONSHIP IS BETWEEN
"CHANGING BANDS" using the BAND+ and BAND- buttons, or
changing
the displayed frequency using the VFO KNOB?  Which am
I supposed to use?  

At one point, I could not get into the "80meter band"
with the BAND- button, without lowering the displayed
frequency down to near 40 meters or lower.

VCO Alignment - requires going from Band 80 to 40 to
30 to 20 to 17 to 15 to 12m to 10m.   DOES THIS MEAN
TO DO IT WITH THE BAND+ switch or with the VFO Knob?

I tried the VCO Voltage Readings - using
band/frequency changes with the VFO Knob.  But then
when I tried to get
the low freq and high freq voltage measurements - I
seemed to be getting a steady stream of "8 volts DC"?

HELP - can someone give me a hint on how to attack
these VCO ALIGNMENT FREQUENCY CHANGES and
measurements?

Thanks,
Fred Osborne N3CSY
FL
4/22

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[Don Wilhelm-3]

Fred,

If you attempted to change bands by moving the VFO knob, you may have the
bands quite skewed.  I would first try doing a 'Direct Frequency Entry' on
each band (see K2 manual page 92) to get things straightened out again.
Then afterward, use the BAND+ and BAND- buttons to change bands.

Yes, your PLL range is just fine - concentrate on the VCO alignment (voltage
at R30) - get that correct before moving on to anything else.

Adjust the voltage at R30 to somewhere between 6 volts and 6.5 volts while
tuned to 4000 kHz (after setting the band to 80 meters), then switch to 40
meters and check the R30 voltage at 7000 kHz - if you have the standard
stuff for the K2, you should see between 1.8 and 2.2 volts at 7000 Hz.  If
these 2 points are within the normal range, all others should fall within
range.  CAUTION: if you have installed the 'rework eliminators', the
procedure is quite different, and the results may be quite confusing - I
have attempted to convince the 'rework eliminator' guys to avoid installing
D19 and D20 and changing the value of C71 for this very reason, but they
have not 'seen the light'.  Unless the K60XV is actually installed, the low
R30 voltage extreme at 5300 kHz cannot be observed, and correct alignment of
the VCO R30 voltages is like taking a 'stab in the dark'.

(Sorry for the RANT Gary, but the fact is that this condition is true and
valid - D19 and D20 and C71 change the VFO range significantly - all other
wiring for the K60XV can be added, but the D19, D20 and C71 should be
delayed until the K60XV is actually installed).

73,
Don W3FPR

> -----Original Message-----

>
> I've gotten to Alignment & Test, Part II RF Board
> build on my K2 # 5422.
>
> I seem to be having problems with "VCO Alignment"
> problems:
>
> a. 4 Mhz Oscillator Calibration = gave a reading of
> 12099.35 - OK it appears.
>
> b. PLL Reference Oscillator Range = 12099.32 high, to
> 12085.65 low - Range = 13.67khz - seems OK
>
> c. VCO Test:  Frequency counter probe to VCO Test
> Point TP1.  I got a frequency counter reading of
> 8913.18, seemingly stable - and OK.
>
> I'm trying to do VCO Alignment, and adjust Inductor
> L30 - to adjust and measure the VCO control voltage
> for
> proper range.
>
> I'M NOT SURE WHAT THE RELATIONSHIP IS BETWEEN
> "CHANGING BANDS" using the BAND+ and BAND- buttons, or
> changing
> the displayed frequency using the VFO KNOB?  Which am
> I supposed to use?
>
> At one point, I could not get into the "80meter band"
> with the BAND- button, without lowering the displayed
> frequency down to near 40 meters or lower.
>
> VCO Alignment - requires going from Band 80 to 40 to
> 30 to 20 to 17 to 15 to 12m to 10m.   DOES THIS MEAN
> TO DO IT WITH THE BAND+ switch or with the VFO Knob?
>
> I tried the VCO Voltage Readings - using
> band/frequency changes with the VFO Knob.  But then
> when I tried to get
> the low freq and high freq voltage measurements - I
> seemed to be getting a steady stream of "8 volts DC"?
>
> HELP - can someone give me a hint on how to attack
> these VCO ALIGNMENT FREQUENCY CHANGES and
> measurements?
>
> Thanks,
> Fred Osborne N3CSY
> FL
> 4/22
>
>

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