Grounding of Crystal Cans

Here are several suggestions from our customers on how to solder the ground wires to crystal cans in the K2.

Note: The recommended ground wire position for X7 - X11 is the opposite of this picture - on the side of the crystal towards the side of the K2 (To the right when viewed from the front of the K2.) , and towards the bottom of the crystal can. This picture was shot on one of our original prototype K2s.


Date:    Thu, 8 Jul 1999 17:32:30 -0700
From:  "Jim Boyle - K6JMB" <jmb@cruzio.com>
To:      "Elecraft Reflector" <elecraft@qth.net>

Ok, I have to admit I'm a newbie.  And I've been trying to be careful and patient with everything I'm doing; but grounding these crystal cases is driving me nuts.  I had the same problem on my "dry run for the K2, the Norcal40A"; and squeaked by;  but I'm not real happy with the result there either.

When I try to solder the ground wire to the top of the crystal case, the solder doesn't "stick" to the case and I don't get a solid & clean joint. Eventually, if I keep trying, I do get it to stay; but I'm worrying about heating up the crystal case too much.  I've tried swabbing the top of the case with a little alcohol in hopes of removing any oil from my hands that might be causing the problem - no change. The solder just doesn't hold very well to the crystal case.  I'm using Kester "No-Clean" solder per Wayne & Eric's recommendation.

I'm kind of embarrassed to ask, but I hafta be doin' somethin' wrong....what is it?   ....duh!


From:  Wayne Burdick <n6kr@elecraft.com>

Thanks for being careful to not over-heat the crystals. I haven't fried one yet, but it is possible.

As for soldering the ground wires: I have a roll of the Kester 44 solder and a Weller WCC100 soldering station (one of their low-priced models). With the iron set for 800 degrees F, I had no trouble soldering to the crystal can. It should take only 2 to 3 seconds.

(The Weller WTCPT soldering station also does a great job with it's stock 700 degree tip. - Eric)

While you may be right about cleaning the can before soldering, I haven't had to do that myself. I think the issue is actually one of heat and soldering iron tip size. I use a 1/10" tip for such things, and it's important to make good, solid contact with the can using the flattest side of the tip. 800 degrees is fine for this operation, too. Is possible that you have either too low of a tip temperature or are using a very skinny iron tip?

By the way, grounding the cans is important. It affects the frequency, bandwidth, filter "blow-by," etc., to a moderate degree.


From: Jay Bromley <w5jay@alltel.net>

Try Scotchbrite (I probably spelled it wrong) on the area you are fixing to solder to.  It will look polished and it might help to tin that area afterwards.  Most crystals have oxidation on their cases that is hard to solder to.

Jim, I also use two Weller 25 watt pencil irons with different tips.  The tip I use on circuit boards is like # ST7 and for crystals, wide traces, solder lugs that are close to a chassis I use a wider tip (sorry I don't have the number), but it is around 3/16 wide flat blade. Sometimes I use this tip on plated through holes that are part of the ground plane.

Anyway as you know the trick is to have enough heat to do the job quick but not hot enough to kill the crystal.  The bigger tip helps by holding and transferring more heat to a wider area.  I even got to where I can use the fine point with success as long as I use most of the tip from the front to a 1/4 inch back toward the handle.

Jim it just takes experience but practice on some surplus crystals, the finish joint on the crystal should look like you flowed it from a glue gun.  Try to heat both parts evenly and a dab of solder on the tip may help transfer some of the heat faster.  Also make sure the tip is tinned and clean.

Also let your iron stabilize for 15 minutes and make sure the tip is tight with a pair of pliers.  Use good solder like the Elecraft Boys recommend.  I am not Dr. Solder and you will get better with each rig!!


From: Tom Hammond - N0SS <n0ss@earthlink.net>

I use a pretty 'warm' iron... about 750-800 degrees, and TIN the top CORNER of the xtal can first.  Then I solder the wire to the PC board, bend it over the top of the xtal can, let it spring away a bit (as it will want to do), lightly TIN the BEND in the wire, hold the tinned bend up against the tinned tin corner and hit it with a hot iron again.  If your iron is a decent temp., the joint should be just about instantaneous.

Note that some irons run too cool for good PC board soldering. With these irons you will find that it takes much longer to make a good joint than with an iron in the 730-750 degree range. 730-780 degrees isn't too hot IF you are the least bit careful about how you handle the iron.

And, I try to TIN just about ANY connection which doesn't involve soldering a wire thru a pre-tinned PC board hole.  Sure makes making the connections a LOT easier in the long run.


From: "Robert Cerreto" <tonybob@centuryinter.net>

Tom gives good advice about tinning your wires. I was taught many years ago to tin wires and larger surfaces (such as your Xtal can) prior to attaching them together.

Two other things you might check into. Make sure the can is clean and free of oils from your hands. I have very oily skin (please no ethnic jokes in front of the guys Tom). There are many occasions where I have to clean surfaces before soldering or gluing. A little denatured alcohol works fine.

Also, if you use a low flux solder, it pays to keep a can of rosin core paste flux on the bench. It only costs a couple of bucks but, a little bit will make these types of connections easier and cleaner. Don't use a lot!! Brush a small amount on the can. I use the flux on my coax connections too and it makes the joints much better looking and reliable. Again, just make sure to use it sparingly. Almost any electronics supply company ( I like Mouser) sells this stuff.

Our tip temperatures here are about 780 degF, if you can believe the solder station LED'S

Love that K2 Jim. It will bring you much happiness.