Mod: Improving Temperature Stability of K2

[Elecraft mailing list]

Hello K2 enthusiasts.

I’m installing the “Improving Temperature Stability of the Elecraft K2 Transceiver 11/15/2002 Rev. H” mod into my old radio. It’s going smoothly except for confusion on my part about one of the capacitors.

The original C174 is to be removed, it is marked “331” which is 330 pF.

The replacement in the kit envelope is a “390” 39 pF cap. But the instructions are confusing, because they say that the replacement should be 82 pF. And then, according to the instructions, if that turns out to not be enough, you can add more capacitance up to 200 pF at C174—or if desperate, add turns to the toroid L33.

My guess is that somewhere along the line the number of turns on L33 was changed to match a 39 pF cap, and the instructions fell behind. Does that make sense? Or should I hunt down an 82 pF cap?

Thanks for your support!

Doug, W0UHU.


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[Don Wilhelm]

Doug,

I have doubts that the toroid for L33 has been changed.

C174 should be 82pF - call support to get a proper capacitor.
Do not remove turns from L33.

The BFO should come into range with those values.  Check the high and
low frequencies before doing anything else.

73,
Don W3FPR

On 10/2/2020 10:27 PM, Douglas Hagerman via Elecraft wrote:

> Hello K2 enthusiasts.
>
> I’m installing the “Improving Temperature Stability of the Elecraft K2 Transceiver 11/15/2002 Rev. H” mod into my old radio. It’s going smoothly except for confusion on my part about one of the capacitors.
>
> The original C174 is to be removed, it is marked “331” which is 330 pF.
>
> The replacement in the kit envelope is a “390” 39 pF cap. But the instructions are confusing, because they say that the replacement should be 82 pF. And then, according to the instructions, if that turns out to not be enough, you can add more capacitance up to 200 pF at C174—or if desperate, add turns to the toroid L33.
>
> My guess is that somewhere along the line the number of turns on L33 was changed to match a 39 pF cap, and the instructions fell behind. Does that make sense? Or should I hunt down an 82 pF cap?
>

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[Elecraft mailing list]

It turns out that the 82 pF cap I was looking for in the BFOMDKT kit is actually in the K2ATOBKT kit.

In addition to some parts consolidation, the Upgrading the Elecraft K2 to Revision B (K2ATOBKT) instructions seem to over-ride or modify some of the instructions in the earlier upgrade kits. Mostly in the area of the sequence of alignment. I will go through all the instructions now to get them synchronized.  :-)

Thanks, Doug W0UHU

—

>
> Doug,
>
> I have doubts that the toroid for L33 has been changed.
>
> C174 should be 82pF - call support to get a proper capacitor.
> Do not remove turns from L33.
>
> The BFO should come into range with those values.  Check the high and
> low frequencies before doing anything else.
>
> 73,
> Don W3FPR
>

---

> On 10/2/2020 10:27 PM, Douglas Hagerman via Elecraft wrote:
>> Hello K2 enthusiasts.
>>
>> I?m installing the ?Improving Temperature Stability of the Elecraft K2 Transceiver 11/15/2002 Rev. H? mod into my old radio. It?s going smoothly except for confusion on my part about one of the capacitors.
>>
>> The original C174 is to be removed, it is marked ?331? which is 330 pF.
>>
>> The replacement in the kit envelope is a ?390? 39 pF cap. But the instructions are confusing, because they say that the replacement should be 82 pF. And then, according to the instructions, if that turns out to not be enough, you can add more capacitance up to 200 pF at C174?or if desperate, add turns to the toroid L33.
>>
>> My guess is that somewhere along the line the number of turns on L33 was changed to match a 39 pF cap, and the instructions fell behind. Does that make sense? Or should I hunt down an 82 pF cap?
>>
>
>

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[Don Wilhelm]

Doug,

Do the K2ATOBKT first, and where those instructions indicate, do the
BFOMDKT and the other auxiliary kits.  That will synchronize them for you.

73,
Don W3FPR

On 10/5/2020 4:55 PM, Douglas Hagerman via Elecraft wrote:
> It turns out that the 82 pF cap I was looking for in the BFOMDKT kit is actually in the K2ATOBKT kit.
>
> In addition to some parts consolidation, the Upgrading the Elecraft K2 to Revision B (K2ATOBKT) instructions seem to over-ride or modify some of the instructions in the earlier upgrade kits. Mostly in the area of the sequence of alignment. I will go through all the instructions now to get them synchronized.  :-)
>
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