Re: More SB-101 Help?

[Diane Swynar]

Dave,

I absolutely KNOW for a fact that those crystals DO, indeed, change
frequency over time---but I've never, ever heard of one changing THAT much
(anywhere from about 1- to 5-KHz, though, I've seen)...

Best bet is to swap that crystal with one in a local buddy's rig (hopefully
there are other Heath adicts in your area!), & see what happens. Try
dropping those non-starting crystals into some generic crystal oscillator
circuit & see if they take off (they say that a Pearce circuit will get
just about anything started, assuming the crystal is OK in the first
place). If they do work there, then suspicion falls upon the hardware
within your own rig...

Sometimes something as simple as swapping the tube in the oscillator
circuit can make all the difference in the world, too, so don't rule that
out...

Good luck!

~73~ Eddy VE3CUI - VE3XZ






> Dave -
>
> A red flag for me was your statement that the crystals for 21, 28 & 29
> MHz wouldn't start.  Crystals don't usually fail en masse.  I would
> suspect a problem with the oscillator circuit.  The 20 KHz frequency
> error points in the same direction.  Mistuning of an oscillator can
> sometimes pull the crystal frequency a lot.  In fact, a broken slug can
> cause erratic problems, and it's quite possible that you didn't break
> it;
> it could have been broken before you got the radio.
>
> One way to remove a broken slug is to epoxy the broken pieces to the
> end of a broken twist drill of an appropriate size.  What?  You don't
> have a broken twist drill; I thought hams saved everything.  Never
> mind.  Cut a chunk out of an old coat hanger (they come in various
> thicknesses) and bend one end into an "L" like an Allen wrench.  Sand
> off the coating on a half inch of the other end, so the glue can get a
> good grip on the metal.
>
>
> Mix up just a tiny bit of two-part epoxy and coat the sanded end of the
> wire.  Be careful not to touch any part of the inside of the coil form
> with the glue during the next step.  Use two hands and something to
> brace them on, and carefully insert the glue end into the broken pieces
> of coil slug.  Twist the tool a bit to "shmooey" the glue so that all
> the broken pieces will be captured.  Clip an alligator clip (use the
> clip only, no wire attached) to the makeshift tool, just above the top
> of the coil form so that the clip will rest on the top of the coil
> form, then let it sit undisturbed for several hours to fully cure the
> epoxy.
>
> The last step is to CAREFULLY remove the slug and tool from the coil
> form.  Paper coil forms are usually slathered in beeswax to keep the
> slugs from moving.   Here's a tip to make removal easier.  Hold the
> business end of a soldering iron or gun near the coil form (no closer
> than a quarter-inch) long enough to soften the wax, then turn the slug
> out before the wax hardens.  This trick can also be used during
> alignment and will prevent breakage in the first place.
>
> I keep a lump of beeswax at the workbench for tightening up loose
> slugs. Use a pen knife to shave a small bit of wax on top of the loose
> slug, then carefully heat the form as before.  In all cases, keep the
> iron from actually touching the coil form.  And never, ever use candle
> wax.
>
> You indicated you had been through the alignment procedure.  Visually
> check coil slugs to make sure none of them are completely out of the
> winding area.  If you find one that way, turn it into the center of the
> coil and try the alignment again.    Enough said.
>
> Good luck.    ;)
>
> Kevin  N2IE
>
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