[aprssig] Kenwood TH-D7A(G) Retired

[Dave Baxter]

Hi..
 
Yes the whiskers are a problem, as is already said, that is why the
military, airospace, medical and safety types are still permitted to use
the full fat 60/40 stuff.   As is anyone for repairs to existing
equipment.
 
The silver loaded solder was originaly used at Tek in among other
products, the early 500 series 'scopes and accessories (remember the
little reel of the stuff in the 500 series?) so any field repairs would
not weaken the joint between the solder "tag" and the ceramic strip that
held it.
 
As an ex Tektronix type, I spent 3 years doing bench service and cal's
in the UK, at both Harpenden and Maidenhead, starting out on 'scopes,
ending up at one point as "The" person this side of the pond for Spec'
An' repairs and service.  Not that I got any recognition or exra pay
when needed....
 
I remember many units coming in for rework after a "third party" had
been inside with ordinary 60/40 solder, the joints were fine, but they
had come away from the ceramic, as a casting comes out of a mold.
Reworking them to replace the ceramic strips was a bit of a chore, to
say the least.   (And replacing the missing spool of "Tek" solder!)
 
It was also a "Eutectic" mix, so there was little to no "plastic" region
as it cooled, so making the joint much stronger mechanicaly, and very
"bright" to the eye, aiding quality control, any "Dull" joints were
imediately suspect..
 
Funny how the "modern" lead free stuff looks like a bad joint, even when
it's suposedly a good one...   And how we've tried to use the stuff for
hand assembly.  But it's nigh on imposible to get a reliable joint
without a great deal of care and preperation.
 
Thankfully, here in the UK, you can still buy 60/40 Tin/Lead solder (and
the silver loaded stuff) from industrial suppliers, so all is not lost.
Yet.....
 
Happy days...
 
73.
 
Dave G0WBX.
 
 
 



________________________________

	From: Shanon KA8SPW [mailto:ka8spw at sbcglobal.net] 
	Sent: 13 October 2008 17:39
	To: TAPR APRS Mailing List
	Subject: Re: [aprssig] Kenwood TH-D7A(G) Retired
	
	
	Why do you think they came out with silver solder as used in
Tektronics scopes?
	
	

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