Strange high frequency push pull transformer action

[...]

Not always, I've seen device leads that have gotten so hot that they seem to weld to the pad or via. A soldering iron won't melt the lead (or whatever it's become).

The old solder is oxidized. I've found that adding some fresh solder (With a mild RMA flux) helps disolve the old crap.

Our processes are all RoHS, so I do the same. The first thing I do when soldering a part is add leaded solder to the socialist solder. I usually take the excess off with some solderwick.

I would hardly call adding leaded solder to a joint a RoHS process. How certain are you of only leaving the allowable 0.1% lead in a repaired solder joint?

--
Mike Perkins 
Video Solutions Ltd 
www.videosolutions.ltd.uk

He's not in Europe.

Quick and dirty: Take the transformer out of circuit, excite the secondary at, say, 5MHz. With respect to the terminal you think is the center tap, look at what you think are both primary ends with a scope. They should be antiphase, and reasonably equal. If not, you've found it.

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)

: 2

eem

lder

It's not socialist solder, it's "we-don't-want-to-make-children-dumber solder".

krw is a classic example of why this is probably a good idea.

--
Bill Sloman, Sydney

Idiot. I'm an engineer. Nothing I touch with an iron goes to customers. I can do anything I want with it.

So you have the peer-reviewed journal articles illustrating a medically and economically important improvement in life quality and expectancy resulting from the reduction or elimination of lead from electronic circuitry, which is traditionally disposed of in landfills, where the lead content has been proven to leach out into the nearby aquifer?

Socialist Solder, I like it.

Tim

--
Deep Friar: a very philosophical monk. 
Website: http://webpages.charter.net/dawill/tmoranwms

Intermetallics. Copper and tin form hard, higher-melting-point compounds when heated sufficiently for diffusion to take over.

It's more noticable when attempting to dismantle copper plumbing*, where tin solder is used (usually with antimony, rather than copper or silver, to harden it), the joints are tight, and the temperature control is poor. If the age alone doesn't do it, overheating a sticky joint can make it set up that much harder!

*Gee, we [humanity] haven't used plumbum (lead) for "plumbing" in over a century. Maybe we should call it cupring (cuprum = copper) or something? Heck, even copper is falling out of favor these days for chincy plastic snap-together things. Go figure...

Tim

--
Deep Friar: a very philosophical monk. 
Website: http://webpages.charter.net/dawill/tmoranwms

--
Lucky customers!

I was aware of that, but its not unknown for US and other countries to adopt RoHS in order to export to Europe. Its a smart move to broaden your market. Therefore any work ought to use lead free solder except in specialist areas. It's also a good idea to prototype using RoHS materials just in case there are any potential manufacturing issues and reliability.

There is the contradiction that on the one hand where he says "Our processes are all RoHS, so I do the same" and then says "The first thing I do when soldering a part is add leaded solder to the socialist solder".

It hardly sounds the "same" and it's a shame that anyone who might point out this contradiction is apparently an idiot engineer.

--
Mike Perkins 
Video Solutions Ltd 
www.videosolutions.ltd.uk

It's also done because some non-RoHS parts are impossible to come by.

Maybe. Some have *no* interest in the europeon market. We do, but that's a different discussion.

Complete bullshit. We don't even *have* RoHS solder in our lab. Engineering manufacturing.

Utter nonsense.

I do the same, meaning pollute the connections, first, with leaded solder. Are you illiterate? I suppose so...

It really isn't my problem if you can't read. What a moron!

You're about as stupid as they come,UsuallyWrong.

It never completely unloads, there will always be capacitances in the transformer and in the FET.

--
Regards, Joerg 

http://www.analogconsultants.com/

Not all electronics fall under that crap ROHS lead free requirement. I would think you would be aware of that and ask what he was doing, rather than jump on his ass.

It was meant as a quip as much as anything and I apologise to krw if it was right not taken as such.

The basis of my post is that generally companies are very sensitive to employees suggesting that they run roughshod over their procedures without qualification, and to be honest I'm surprised at krw's response. If I import equipment into Europe I become responsible for it, and I carry the can if it falls short of the legal standards it must conform to. Therefore if I knew a supplier had employees that were boasting they use leaded solder, I'd be concerned as it's trivial to check for lead free solder by the likes of Trading Standards.

--
Mike Perkins 
Video Solutions Ltd 
www.videosolutions.ltd.uk

I like that!

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

I thought that was how you prepped them for playing the blues. :-)

Ed