KSB2 Problem: Big attenuation of received signals

[Andrew Meier]

My first post, this is regarding my attempt to install
the KSB2 option into my K2/100 #4363.

I built the KSB2 option, and removed C167 and the two
jumpers from the RF board, plugged in the KSB2 board,
applied power, and got the "Elecraft" on the display.


The problem is that the receiver became very quiet. I
could still hear the strongest signals if I turn the
AF Gain way up, and instead of S9 on the meter,
they're way down to S1. The KSB2 manual specifically
states (page 15, final step of "initial test") this
should not happen, and if it does, to go to the
troubleshooting section.  I confirmed about half of
the DC measurements in the troubleshooting section. I
noticed when I jiggle around RFC2 I get some noise in
the receiver, and those little RFC1 & 2 toroids on the
KSB board were a challenge to wind, so I'm wondering
if I have a problem there.

I removed the KSB2 board, put the jumpers and the C167
back into the RF board, and now I am back to my
well-performing K2/100.

The KSB2 board is sitting on the bench waiting to be
fixed.

Have any of you seen receiver attenuation problems
when you first plugged in the KSB2? What was your
solution?

Thanks,
-Andrew, KF7HB




               
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[Don Wilhelm-3]

Andrew,

Plug the KSB2 in again and be certain that it is properly positioned on the
headers.  It is easy to misplug the KSB2 - if you see the standoff and TP2
properly aligned with the holes in the SSB board, it probably is mounted
correctly.

As a check (but not a permanent fix) slide a small sheet of paper between
RFC1 and RFC2 and the adjacent crystal cans.  That is a quick check of
whether or not the windings of the chokes are shorting to the crystals - if
they are, rewind the chokes being careful not to scrape the insulation on
the wire.

Check the orientation of the diodes - all of them should have the banded end
away from the board.

Lastly (or maybe best doen first) check the soldering carefully,
particularly in the crystal filter area.

73,
Don W3FPR

> -----Original Message-----
>
> The problem is that the receiver became very quiet. I
> could still hear the strongest signals if I turn the
> AF Gain way up, and instead of S9 on the meter,
> they're way down to S1. The KSB2 manual specifically
> states (page 15, final step of "initial test") this
> should not happen, and if it does, to go to the
> troubleshooting section.  I confirmed about half of
> the DC measurements in the troubleshooting section. I
> noticed when I jiggle around RFC2 I get some noise in
> the receiver, and those little RFC1 & 2 toroids on the
> KSB board were a challenge to wind, so I'm wondering
> if I have a problem there.
>
>

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[Vic K2VCO]

Andrew Meier wrote:

>  I
> noticed when I jiggle around RFC2 I get some noise in
> the receiver, and those little RFC1 & 2 toroids on the
> KSB board were a challenge to wind, so I'm wondering
> if I have a problem there.

Be sure to check for PTTL (Poorly Tinned Toroid Leads).

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco

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[Ron D'Eau Claire-2]

> The problem is that the receiver became very quiet. I
> could still hear the strongest signals if I turn the
> AF Gain way up, and instead of S9 on the meter,
> they're way down to S1. The KSB2 manual specifically
> states (page 15, final step of "initial test") this
> should not happen, and if it does, to go to the troubleshooting
> section.


Andrew: Don's suggestions are right on track. I have one to add, assuming
this is a new build. Check for d-c continuity from each pin of each crystal
to ground. It should be an open circuit for d-c. If not then most likely you
used enough solder to form a small fillet around the pad. On the crystal
side of the pad, the fillet easily shorts the signal path to the crystal
case and so to ground.

If so, then remove the crystal involved, clean off the solder, the carefully
replace it, using a minimum of solder. (Note that you have jumpers across a
couple of capacitor locations, so a short there will require that you open
the jumper to see which crystal is involved).

Ron AC7AC



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