How to spot a dry joint, (fixing relay units or ecu)

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How to spot a dry joint, (fixing relay units or ecu)
Topic Started: Mon Aug 17, 2009 9:50 pm (200 Views)
kentronix	Mon Aug 17, 2009 9:50 pm Post #1
Admin Posts: 16,358 Group: Admin Member #147 Joined: January 20, 2006	This can be a bit of an art as often they are almost impossible to see but after opening up my fuel pump relay I noticed a couple of good examples. One is probably the average type and the other is one of the hard to spot ones. Ignore the obvious half arsed repair above them, it was just a burnt out track and I was in a rush.... OK Roughly what you see with an eye and a magnifying glass :- Lets get a bit more light on that :- A bit of photoshopping to bring out the detail. And the money shot !! All you need to repair one is a soldering iron, heat it up fully until its all liquid and then let it cool slowly. I tend to remove some of the solder and redo it with new solder but thats not really needed. Edited by kentronix, Mon Aug 17, 2009 9:52 pm.



chrismatheou	Mon Aug 17, 2009 9:55 pm Post #2
Enthusiast Posts: 1,478 Group: Members Member #789 Joined: January 4, 2007	From the first shot I would have never noticed that them two on the left were dry!



kentronix	Mon Aug 17, 2009 10:00 pm Post #3
Admin Posts: 16,358 Group: Admin Member #147 Joined: January 20, 2006	I have a lot of experience spotting dry joints and I only noticed the one on the right, while looking closer through my camera I did notice the left one and the lower one only came out in photoshop, its not actually failed as the bent over prong is holding the joint firm but best to redo it. I just noticed another one thats failed although still held tight so probably doesnt effect operation yet and is very hard to spot. First one to spot it wins the old solder once I have removed it.



chrismatheou	Mon Aug 17, 2009 10:07 pm Post #4
Enthusiast Posts: 1,478 Group: Members Member #789 Joined: January 4, 2007	Hmm I'm going to guess that big fat one in the middle? How do you take away the old solder anyway, with one of them solder sucker things cos they look like quiet big blobs lol?



kentronix	Mon Aug 17, 2009 10:15 pm Post #5
Admin Posts: 16,358 Group: Admin Member #147 Joined: January 20, 2006	The new one I found is only visible (and only just) in the 3rd pic down. I use a spring loaded solder sucker. You can also use solder removing braid, the rubber sucky bulb things or just the pick and flick method transferring from iron to a moist sponge. The only problem with the spring loaded ones is they are so much fun I tend to just slide, boing, slide, boing, with my left hand constantly when soldering. I get through them at an alarming rate !!



kentronix	Mon Aug 17, 2009 10:25 pm Post #6
Admin Posts: 16,358 Group: Admin Member #147 Joined: January 20, 2006	Found a couple more :- Just goes to show, if you got the soldering iron out, you may as well spend 10 mins doing them all. Some only showed up when photoshopped.



matsalleh76	Mon Aug 17, 2009 11:35 pm Post #7
Matsalleh76 Posts: 141 Group: Members Member #447 Joined: August 9, 2006	Excellent & informative post. Thanks. bobf.



deekerh	Tue Aug 18, 2009 5:46 am Post #8
Deekerh Posts: 331 Group: Members Member #664 Joined: November 14, 2006	Very interesting, those pictures really highlight a fairly common problem especially in older circuit boards. Thanks



alogaparaloga	Tue Aug 18, 2009 6:11 am Post #9
crazy mind Posts: 613 Group: Members Member #2,419 Joined: March 14, 2008	Just a comment... At the burnt spot you have to clean it so that surface corrosion disappears, and then put some Araldite or other epoxy to seal it from the environment. Corrosion always introduce more resistance in the circuits and is common failure in many repaired PCBs Regards Menelaos Edited by alogaparaloga, Tue Aug 18, 2009 6:16 am.



balamb37	Tue Aug 18, 2009 5:39 pm Post #10
Member Posts: 569 Group: Members Member #3,881 Joined: February 25, 2009	This 'Post' needs 'Pinning' at the top, at the moment there is more and more 'Relay' probs and it is surprising how many don't know that it's an easy fix, just needs a steady hand and a suitable soldering iron. and as one can see a good magnifying glass to find. A Very good post kenny. Edited by balamb37, Tue Aug 18, 2009 5:40 pm.



stwat	Tue Aug 18, 2009 5:43 pm Post #11
Moderator Posts: 12,434 Group: Moderator Member #28 Joined: November 11, 2005	I quite agree. Pinned.



balamb37	Tue Aug 18, 2009 5:45 pm Post #12
Member Posts: 569 Group: Members Member #3,881 Joined: February 25, 2009	Good on yer, now get looking for the loose contact,



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