K3 - HAGCMDKT mod kit

[dhhdeh]

Hi Everyone,

I own K3 #371 and have entirely delighted with it and the Elecraft
experience to date.

But I do have a small nit to pick with the HACG mod and some comments
posted earlier today.

After doing a lot of pre-modification research on my #371, I determined
that the mod had been done, only partially, before it was shipped to
me.  The R33 and R40 were still in place and not removed or jumpered as
the mod instructed. They both appeared to be 1K ohm SMD resistors.

Before proceeding further with the mod, an inquiry to K3 Support at
Elecraft instructed me that my board only had a 'portion' of this mod
performed and that R33 and R40 should definitely be removed or shorted.
When I discussed my situation with several of you privately no one was
sure why my K3 had only a portion of the mod performed before its shipping.

So away I go last weekend and proceed remove the two SMD resistors and
replace them with jumpers per the HAGC instructions.

Now, today, I read Eric's post indicating that this was indeed a
'factory mod' and the removal of the R33 and R40 is optional, ok either way.

Here's my issue.

In removing the SMD devices (which I undertook as suggested by first
cutting them in half with miniature dikes to avoid the necessity of
using too much heat to the pads on the pc board) I very briefly applied
heat from a 20 watt iron and solderwick for a fraction of a second to
remove the remnants of the devices.  Not only did the remnants come off
but so did one of the solder pads from the pc board. So much for my
introduction to SMD de-soldering.

While these boards are indeed elegant in design and construction, they
are apparently quite fragile and do not lend themselves to ANY excesses
in heat. Frankly I was unpleasantly surprised.

So I had to scrape off the solder resist back along the trace and solder
the jumper back on the trace away from the now missing pad. All's well
and the K3 runs fine BUT my once elegant pc board now is a bit butchered
around where R40 once resided.

Now today I read that this step in the mod was not needed to be done. I
only wish I had known that before I started this adventure.

So should R33 and R40 be left in place or removed?  I do not understand
how it does or does not make a difference either way.  IMO that should
have  been addressed in the HAGC mod instructions.

Had I read today's post earlier I would never have undertaken this mod.
I wish I had received the entire story from K3Support earlier on.

Really not a big deal but it irked me a bit.

Morale of my story is proceed very carefully in undertaking soldering on
these boards.  They can be unforgiving.

BTW the 'CW rise time mod' was not performed on my unit. That was done
with no problem. I used the through hole capacitor on this one.

In closing how's my K3 you ask?  IMO the finest transceiver I have ever
used. Bar none.

73 de N1LQ-Dave



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[Bill W4ZV]

Hi Dave,

Dave you indeed had an unfortunate experience!

>After doing a lot of pre-modification research on my #371, I determined
that the mod had been done, only partially, before it was shipped to
me.  The R33 and R40 were still in place and not removed or jumpered as
the mod instructed. They both appeared to be 1K ohm SMD resistors.

Rather than using visual inspection, I recommend everyone use a VOM to actually measure R33 and R40.  Apparently the factory mod uses SMD resistors with very low resistance instead of an actual short.  Most SMD resistors are marked with 3 numbers such as "333"  The first two digits are the first two significant digits and the second is a power of 10 multiplier.  Thus "333" signifies 33 x 10^3 = 33k ohms.  I'm actually not sure what markings are on the factory SMD shorts but they should include that in the mod instructions.  I've sometimes seen "000" used for SMD shorts but the safest thing is to measure them, and both R33 and R40 can be accurately measured "in-circuit", so trust your measurements.  

>Here's my issue.

>In removing the SMD devices (which I undertook as suggested by first
cutting them in half with miniature dikes to avoid the necessity of
using too much heat to the pads on the pc board) I very briefly applied
heat from a 20 watt iron and solderwick for a fraction of a second to
remove the remnants of the devices.  Not only did the remnants come off
but so did one of the solder pads from the pc board. So much for my
introduction to SMD de-soldering.

Rather than removing R33 and R40, another alternative is to simply place a short across them.  This can be done easily by soldering a small piece of component lead wire bent into a U across the existing resistors.

>So should R33 and R40 be left in place or removed?  I do not understand
how it does or does not make a difference either way.  IMO that should
have  been addressed in the HAGC mod instructions.

It doesn't matter as long as they are shorted, either with a piece of wire across the existing resistors or by replacing them with SMD resistor "shorts".  A short is a short.  I always check my work by checking with a VOM/DMM across adjacent traces (i.e. in series with the SMD pads).

>Morale of my story is proceed very carefully in undertaking soldering on
these boards.  They can be unforgiving.

If you've never done this before, I suggest practicing with some scrap SMD boards first.  Most of us have some old scrap SMD boards in our junk box and this is a good way to practice your technique before touching the K3.

>BTW the 'CW rise time mod' was not performed on my unit. That was done
with no problem. I used the through hole capacitor on this one.

I wonder how you determined that since SMD capacitors are *NOT* marked?  The only way I know is to use a capacitance meter which does give a correct reading "in-circuit".  Unmodified units use 1 uF and modified units use 0.1uF, but they look identical visually.  Again, trust your measurements and not visual inspection.

Someone earlier mentioned the SMD LED orientation.  The correct orientation is with the two tiny green dots toward the front of the K3 (thanks W4WFB).

Sorry you had a bad experience and I hope this helps others!

73,  Bill

[Julian, G4ILO]

Bill W4ZV wrote

Sorry you had a bad experience and I hope this helps others!

Yep, it helped me to decide not to even *think* about doing it!