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Date: Fri, 02 Mar 2001 09:52:26 +0000
From: "J. Ellis" <jellis at viaccess.net>
Subject: Re: [Elecraft] K2 PRE/ATT SWITCH

Steve Banks wrote:

> Hi Gang-
>
> K2 S/N 1599 is close to birth
>
> whenever I turn on the PRE function,
> there is a big DECREASE in received signal Can anyone shed any light on
> whether what I'm seeing with the PRE function is normal?
>
> Steve Banks K0PQ

Steve,

That is not an uncommon problem.
Check T-6, I'll bet you that one of
your leads doesn't have the enamel
removed enough for the wire to make
good contact with the PCB.

G/L es 73,
John, NP2B
k2/1645, k1/426
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Date: Sat, 3 Mar 2001 17:00:37 -0700
From: "Steve Banks" <sbanks2571 at qwest.net>
Subject: [Elecraft] K2 PRE/ATT Switch follow up

Wayne N6KR:
Jim N5IB:
Jim K4ZM:
John NP2B:

Thanks for your suggestions about my misbehaving K2 Preamp.  It is now fixed
and working like a champ!

(New builders take note: I've discovered a new (new to me anyway) way of
installing T6 incorrectly, and you might want to use care when you install
yours.)

To recap briefly FYI, I first reflowed all four solder joints of T6,
thinking that one or more of them surely had to be cold.  It turns out none
of them was at fault, and the Preamp was still dead in the water when I ran
the K2 again!

I then re-benched the K2 and started chasing down whether 12VDC could be
found on the collector of Q21...ZILCH, ZERO, NADA!  The air gap was clearly
somewhere in T6's bifilar winding.

After finding 12VDC on both ends of R74 but not anywhere on the four T6 PCB
connections, I decided to simply remove T6 and completely rewind and
reinstall it, thinking it probably had an open winding.  Well, it
didn't--all four were fine based on what my DVM was telling me after I
removed it.

HOWEVER, the culprit was that the PCB hole where I had connected the T6 red
lead #1 was NOT where it belonged.  The hole I had connected it to was the
empty hole (apparently unused...maybe a manufacturing test point) adjacent
to the mixer, Z6, which is quite close to the correct #1 hole for T6.  I
made the mistake of soldering in T6 leads #3 and 4 first instead of #1 and
2, and that made it tough to verify that I had lead #1 in the right place as
I was finishing up T6.

With the problem now fixed, the 14dB of gain produced by the Preamp is
really outstanding!

Thanks again for your help!

73,

Steve Banks
K0PQ
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Date: Tue, 17 Apr 2001 00:50:41 +0100
From: "J. Ellis" <jellis at viaccess.net>
Subject: Re: [Elecraft] Problem with K2 Preamp

Hi Mike,

Bet you a bottle of Cruzan Rum that the problem
is the toroid. (L6). I went thru the same thing and
have answered several folks with the same problem.
One of the leads is not making good contact with the
PC board. Reheat the connections or in the worst
case, pull the toroid, rewind and get the enamel off,
reinstall and I'll bet you it works good.

I don't know what it is with that particular coil, but
it is a common problem.   :-)   Good luck (but you'll
have to come down to the V.I. in order to collect the
rum since they won't allow us to ship it thru the mail!).

73,
John, NP2B
K1/426, K2/1645

Mike Malone wrote:

> I just completed Phase 2 testing of my K2 and everything came thru fine.  I
> have one problem though.  The preamp on setting attenuates signals more so
> than the attenuator setting does!
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Date: Sat, 29 Sep 2001 08:16:16 EDT
From: Rmwoodchuck at aol.com
Subject: [Elecraft] IF Amp

Hi,

I am doing the I.F. amp alignment on K2 #2250. Other than the typical problem 
of peaking L34 it seems to be going fairly well and I am now receiving strong 
signals. I do have a question about the pre-amp though. On page 61 before you 
begin tuning you are supposed to make sure the PRE annunciator is on. I had a 
very hard time hearing anything when this was on and had to turn it off in 
order to tune the inductors. Is this normal or do I have a problem somewhere?

Thanks
Marie, NG8S

K1 #650
K2 #2250(in progress)

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Date: Sat, 29 Sep 2001 11:03:49 EDT
From: Rmwoodchuck at aol.com
Subject: [Elecraft] Re: IF Amp

Thanks for the replies. It was T6...had the #1 and  #2 leads switched. Makes 
a big difference. 

Thanks again,
Marie, NG8S

K1 #650
K2 #2250(in Progress)

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