[Elecraft] [K2] Odd AGC problem with K60XV installed
Bill Coleman
aa4lr at arrl.net
Mon Dec 7 20:35:12 EST 2020
I’m going to set it up in the damp basement at my other QTH. That’s where I saw the problem originally. Will let you know if it comes back.
> On Dec 7, 2020, at 11:43 AM, Don Wilhelm <donwilh at embarqmail.com> wrote:
>
> Bill,
>
> It does sound like it is fixed. Just be aware that some intermittents do find their way back, so knowing the symptoms you can recognize it quickly.
>
> 73,
> Don W3FPR
>
> On 12/6/2020 6:30 PM, Bill Coleman wrote:
>> Don,
>>
>> I set the K2 up this weekend to try to reproduce this problem. Once again I opened it up and re-installed the K60XV board. I put a scope probe on P1 pin 6.
>>
>> I did not see the AGC failure mode right away, but I did find an intermittent oscillation on pin 6 at about 15 MHz. It would come and go, but no AGC activation.
>>
>> I removed the board and re-soldered all the components around the LM358. Then I inspected the board and scraped away any residual solder flux in that area of the board between any pins.
>>
>> I also re-soldered the 4.0 MHz resonator, although I did not hear or detect any relay activation when it failed before.
>>
>> After that, I put the board back in with the scope probe and ran it on the workbench for a day. I saw no AGC failure mode and no more 15 MHz oscillation.
>>
>> So, maybe it is fixed? Fingers crossed.
>>
>>
>
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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