[Elecraft] K2 AGC Off Problem

[Geoffrey Mackenzie-Kennedy]

If in some cases the value of C8 has to be reduced OR the value of C7 has to 
be increased ( as Wayne suggests ) for proper operation of the 5.068 MHz 
oscillator, it would seem that the original capacitor values result in too 
much feedback in the oscillator. This could be a "batch" problem where some 
crystals have a higher Q than the norm OR the oscillator part of the NE602 
(U1) has higher gain than the norm, or both. IMHO changing the value of 
either C8 or C7 sounds like a good fix, and any small change in frequency 
that results does not matter.

If it is a "batch" problem I would think that it would affect a small group 
of K2s (by serial number) if Elecraft use the crystals / NE602s soon after 
delivery. Whether or not the problem deserves a Builder Alert should be 
suggested by a more experienced "Elecrafter" than I.

73,
Geoff
GM4ESD

----- Original Message ----- 
From: "Nick Waterman" <laptop at noseynick.com>
To: <elecraft at mailman.qth.net>; <webmaster at elecraft.com>
Cc: <va7to at rac.ca>
Sent: Sunday, May 21, 2006 9:36 AM
Subject: Re: [Elecraft] K2 AGC Off Problem


>> Thanks for the message.
>> A 10 pf at C8 did the trick. The receiver is now working properly in AGC 
>> off
>> mode.
>
> Think that's at least 5 or 6 of us on the reflector have had this issue,
> and this easy fix, so far. Does it deserve a builder alert on the
> website yet?
>
> For anyone else: If you are seeing AGC problems (hold PRE/ATT and AGC,
> see if your K2 goes deaf), check your junk box for a 10pF cap and change
> control board C8. Wayne says 680 pF at C7 may be another option. I DO
> NOT recommend this mod UNLESS you're seeing "AGC OFF" issues though.
>
> -- 
> "Nosey" Nick Waterman, G7RZQ, K2 #5209.