[Elecraft] K2 build - VCO control voltage 0 volts

Don Wilhelm w3fpr at embarqmail.com
Sat Oct 26 22:28:01 EDT 2013


Harry,

Make certain you have the bottom cover in place when running CAL PLL - 
yes, it does make a difference!
If you did it with the bottom cover off, no harm, just do it again.

73,
Don W3FPR

On 10/26/2013 10:12 PM, Harry Stone wrote:
> Strange indeed, and here is why, when I was messing with it just now
> measuring again, I laid my arm across the case  and then I got voltage.
>   Somewhere I had something shorting against the case.
>
> I'm back on track now, VCO voltage is in spec for every band.  CAL PLL is
> running now.  When it's done I will double check the bottom of the RF board
> to make sure I don't have something sticking up too high.
>
> Thanks again!
> harry
>
>
> On Saturday, October 26, 2013, Don Wilhelm wrote:
>
>> 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.
>>>>
>>>>



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