Re: K2 - Strange Problem ?

Posted by Stewart Baker on Nov 30, 2004; 12:20pm
URL: http://elecraft.85.s1.nabble.com/K2-Strange-Problem-tp372185p372193.html

On Tue, 30 Nov 2004 07:18:23 -0500, Mike S wrote:

> At 01:24 AM 11/30/2004, Stewart Baker wrote...
>> problem, but I am back with the noise. It is a shame that there is no way
>> to get
>> at the +8V rail on the front panel board as that would be an ideal mic
>> supply.
> The Auxbus connection between the RF board and front panel is unused. You
> could cut the trace on the RF board and use that to bring whatever you want
> across. I don't know if there are any future plans for a different front
> panel which might use that line. Alternately, there may be room to add an
> additional header pin at one end of the RF/FP connection to allow another
> signal. Worst case, you could airwire it with an inline connector.

Well spotted Mike !
I completely missed that route via Pin 7 on P1.
I can feel my headache going already....

As you suggested I will cut the AUXBUS track on the RF board where it goes to
the plug and wire the 8A rail to it. There appears to be plenty of decoupling
already on that rail, but any more that I add should not upset things. It keeps
everything clear of the MCU and other sensitive circuits. This new rail might be
useful to supply other add-ons. I will then disconnect my pre-amp from the 5A
supply, and use an airwire connection to Pin 7 on J1 to feed it.
At this late stage in the K2 development I doubt if the AUXBUS signal to the
Front panel will ever be used.

I may have to tweak the pre-amp circuit values a bit for the increased supply
voltage - but what the heck..

Again, many thanks for your valuable advice.
I will keep you posted as to progress.

73
Stewart G3RXQ

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