[Elecraft] [K2] Forgetful K2 filters

[STEPHEN BUNTING]

Hi All,

To wrap up and put in the mail list archive, my K2 issues have now been
solved. Don, W3FPR suggested looking at U6, U7 and U8.  I changed U7 whilst
the radio was apart and resoldered U6 and U8 to resolve the issue. AE6QL
also pointed out that there may be an issue with the socket for U6, but I
wasn't brave enough to try and remove it as Fred suggested in case I
trashed the board. So far I don't need to make that change. Phew!

Thanks again to the list for helping me with this issue.
73
Steve
M0BPQ


On 17 April 2013 12:59, STEPHEN BUNTING <stephen.bunting at virgin.net> wrote:

> Hi,
>
> I have a K2/100 on my bench that is behaving strangely and I’d like some
> advice.  This has the SSB board and Z10000 buffer amp and 2.04P firmware.
>
> That radio hasn’t been used for some time and I am told it was stored in
> an attic space so will have been subject to temperature swings. Initial
> symptoms were that the radio was deaf and filters misaligned.
>
> Further investigation with spectrogram showed that all the CW filters were
> centred at 900Hz and about 300Hz wide so I started a retune as per N0SS.
> All re-tuned just fine and sensitivity returned. The SSB filters except OP1
> were also misaligned but I haven’t touched them yet. As a CW op I was happy
> to try the radio on the air.
>
> But.....
>
> When I turn the radio off and on again I find that my filter settings are
> sometimes lost and the filters return to 900Hz centre and 300Hz wide.
> Entering the cal fil routine can restore them without me readjusting the
> DAC value.
>
> Furthermore, when I am in user mode (i.e. not cal fil) and tap xfil to
> scroll through the filters sequentially, every so often one filter ends up
> back to the 900Hz center and 300Hz wide. This can be any of the four
> defined filters. If I continue to scroll through the filter set I can
> return to the erroneous filter to find that it is back where I wanted it to
> be i.e. centered at 600Hz . This happens at random as far as I can tell i.e
> any (or no) filter can misbehave in a cycle.
>
> As an aside, when altering the BFO values to tune the filters I randomly l
> got an “INFO 230” message even though the freq counter probe was in place.
> This doesn't seem to be a loose connection as a repeat tune without
> touching anything works just fine. I also have a random sidetone issue
> which may be related. The sidetone disappears every so often and can be
> brought back to life by changing the pitch slightly. If I increment ST P up
> by 1 unit the sidetone reappears instantly. I can then return to my usual
> level of 600Hz and it works again for a while.
>
> The remarkable G3TJP has helped me enormously with all things Elecraft in
> the past, but I feel bad about bothering him with another issue. Any
> thoughts from the team here what to look at next? Replace the firmware chip?
>
> 73
>
> Steve, M0BPQ
>