[Elecraft] K2 s/n 7176 QRV

[Don Wilhelm]

Ron,

If you are going to use your K2 mobile in a vehicle that will subject it 
to excessive vibration, then you concern about R116 and the L33 toroid 
leads is valid.  In normal circumstances (even in passenger car mobile), 
it is not a problem.  Ham radio does not normally build to avionics 
requirements where safety while up in the air (and during takeoff and 
landing) is the greatest concern.

73,
Don W3FPR



On 8/2/2011 7:03 PM, R Thompson wrote:
> On Tue, 2011-08-02 at 09:54 -0400, Don Wilhelm wrote:
>> Ron,
>>
>> The last step in the left column of page 61 directs you to put tape on
>> the bottom cover at the L33 location so the resistor leads do not
>> contact the cover.  If you did that, your suggestion for covering the
>> bare leads of R116 is not necessary.  If you omitted that step, get out
>> your electrical tape.
>     That was done, although there was adequate clearance between the
> lowest point of the assembly and the cover.  What makes me uncomfortable
> is having the bare resistor wire in contact with the fine enamel coated
> coil wires.  Its my experience with avionics that makes me very
> sensitive to the possibility of vibration related damage.
>> On removing the heatsink - that can be done without losing the PA
>> mounting hardware if the K2 is placed on its side so gravity does not
>> pull the screws out.  My favorite technique is to place a square of
>> electrical tape over the screwheads sticking to the top of the board and
>> T4.  Then the screws do not fall out.  Yes, you have to push the screws
>> back a bit to remove the heatsink, and if I am going to leave the
>> heatsink off for an extended time, I will put the nuts on the screws
>> finger-tight.
>> Conformal coating and other "solutions" can get messy if the PA
>> transistors ever have to be replaced.
>     The tape idea is a good one.  The conformal coating was applied wet
> to the insulator stack prior to hold it together, and allowed to get
> tacky dry.  No conformal was applied to the surfaces of the shoulder
> washer that come in contact with the transistor, as you said it could be
> a problem removing it from the transistor without damaging it.  Its not
> something I'd expect others to do as gluing things together could be a
> headache at some point.
>     If I were to build another one for mobile, backpacking, or other
> rough use, there are a few things that I'd do differently but wouldn't
> recommend that others do.
>
>      Thanks Don, and others on this list for the help during assembly and
> making it an enjoyable project overall.
>
>             Ron VE8RT
>> On 8/2/2011 6:57 AM, R Thompson wrote:
>>> Its not in the manual, and others may have a comment on this, but I wish
>>> that I had done it.  On page 60, the installation of L33 using R116, if
>>> I could easily do it over again I would take a few millimetres of
>>> insulation off of the green wire to cover only the parts of the leads of
>>> R116 that come in contact with the top of L33.  I'm uncomfortable with
>>> the bare leads of R116 pressing into the very thin insulation of the
>>> windings on L33.
>>>
>>> Some other things I did I won't promote here, especially after being
>>> told not to do it :-)
>>>
>>> The stack of insulators used on the PA amplifier transistors, when I
>>> took the heatsink off to install the 160M option I took the stack and
>>> used a bit of conformal coating on the loose insulators to stick them
>>> together.  The idea was to keep the three insulating pieces (per
>>> transistor) together as a stack rather than having them fall apart when
>>> the heat sink is removed to install another option, such as the
>>> transverter kit which I'm considering doing later.
>>>
>
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