[Elecraft] K2 build - VCO control voltage 0 volts

[Don Wilhelm]

Harry,

That is quite strange.  I would examine your work carefully, 
particularly looking for lifted solder pads and/or solder bridges.

80 meters should have only C72 in the circuit. You should trace the VFO 
range select path with an ohmmeter by following the path in the 
schematic (checking for continuity) from K15 pin 3 through relays K15, 
K14, and K13 to C72.  Relays K15 and K14 should follow the path shown by 
the closed contacts on the schematic while relay K13 should be "set" 
which means continuity between pins 3 and 4.

73,
Don W3FPR

On 10/26/2013 9:09 PM, Harry Stone wrote:
> Well I spoke too soon.  I replaced that capacitor and now I have 0 volts on
> every band.   Any thoughts?
>
> thanx,
> harry
>
>
>
>
> On Saturday, October 26, 2013, Harry Stone wrote:
>
>> Don,
>>       I know this isn't exactly your first rodeo, but that's still pretty
>> impressive.  I have the wrong component installed at C73, I have a 4
>> <point> 7 pF instead of a 47 pF.
>>
>> Bravo!
>>
>> thanx,
>> harry
>>
>>
>>
>> On Saturday, October 26, 2013, Don Wilhelm wrote:
>>
>>> Harry,
>>>
>>> The thing in the VFO Range Select area that is common between 40, 30 and
>>> 15 meters is C73,
>>> Check its value - it should be 47 pF (marked 470).
>>>
>>> A low voltage at R30 indicates that there is not sufficient capacity in
>>> the tuned circuit and the PLL/VCO is trying to increase the value of the
>>> total capacity.  That means if C73 is the correct value, check its
>>> soldering and the soldering of relay K13 pin 8.
>>>
>>> CAL PLL depends on having the 40 meter frequency range correct, so you
>>> will not be able to do that procedure until you have the R30 voltage in
>>> range on 40 meters (info 232 means the frequency read by the MCU is not
>>> correct (yes there are other possible causes of info 232).  The alignment
>>> steps are sequential, so if one does not give correct results, you cannot
>>> skip to the next one without encountering problems.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>>
>>> On 10/26/2013 6:13 PM, Harry Stone wrote:
>>>
>>>> My VCO control voltage is zero on 40,30, and 15 meters.  All other bands
>>>> are within the normal range, all tests prior to these measurements
>>>> passed.
>>>>    When I try to run CAL PLL, I get info 232 even though I am on 40
>>>> meters.
>>>>
>>>> What should I check first?
>>>>
>>>>
>>>>
>> --
>> Have old memories and young hopes.
>>
>