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Whirlpool 4388932 defrost board (Adaptive Defrost Control)

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To add to a previous post where the problem seemed to be a "cold solder" joint, I recently ran into a great article I want to share.
The previous post location is:;topicseen#new
While I fixed my problem by re-soldering a circuit board I wrote then that I cannot understand why it failed after 20 years (the original refrigerator came with the home).
The article I would like to glean information from came from an IEEE Life Member newsletter, long article, I will just rephrase a few lines.

The name of the article is: "It's Not Cold Solder Joints".
It started with the discovery that if a failing circuit was touched with a hot soldering iron the failure disappeared.   (Note I had added solder as well.)
Long story but when they took a failed board to a lab specializing in failures they noticed an incorrect resistance reading across a suspect diode.
They suspected contamination.  They finally found that if the soldering flux used had even small amounts of chlorine in could cause problems if not washed properly after soldering.

What happened was that small metal whiskers were growing across the diode because of the chlorine contamination and, while it would take some time for the whiskers to migrate from one joint to another, it could eventually cause a failure.  (Is that what happened in my refer after 20 years?)  Heating the joint with a soldering iron would melt away the whisker and led to the wrong "cold solder joint" conclusion.  They repositioned the diode such that the board could be washed better and washed the board twice, once again after turning it 90 degrees to be sure all the flux had been removed.  This solved the problem. 

Though my problem seemed to be an "open" connection to a relay rather than a shorted component, it is still interesting to note that "whiskers" take a long time to cause a "short" type failure.
With such a short type failure perhaps all that is needed is to wash the board off well with a suitable solvent.  Of course now days most people don't attempt circuit board repair, replacing the board with a later release, that has often been revised by the manufacturer, is better.   Often the manufacturer makes several improvements to a replacement board.

Hope you enjoyed this new insight as much as I did.
best, gwakeen   

Hi gwakeen,

Thanks for the additional information.

For what it's worth the previous topic location you referenced with a link is the same topic you posted your recent reply to.

Thanks for posting.  O0

I saw that after posting, thanks.
I had problems going from your email to me telling me that the post had been moved, then signing in and replying properly.
So I quoted the same link thinking that maybe it had been moved.
Confusion by an amateur!
best, gwakeen

No problem. I can understand the confusion.

I have recently added some new boards to our forum and I'm in the process of moving topics from the old boards to the new boards.

Thanks again.


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