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 Post subject: TROUBLE SHOOTING BAD JOINTS CIRCUIT BOARDS
PostPosted: Jan Fri 18, 2019 8:11 pm 
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One thing I found in the 2way radio repair, use 1 thick paint brissel AKA (cats WhisKker) and tickle the area that would equate to the radio's problem esp intermittent problems . Had a commercial Kenwood ht ,intermittent rx audio, after the whisker tick I found the cold solder joint. radio worked fine after that. Use thicker brissels for more stubborn areas. Good luck. EF JOHlNSON TECH.
JR


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 Post subject: Re: TROUBLE SHOOTING BAD JOINTS CIRCUIT BOARDS
PostPosted: Jan Sat 19, 2019 2:14 am 
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Location: Mpls, Minnesota
A ESR tester also works good for finding breaks in PC boards.

Dave


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 Post subject: Re: TROUBLE SHOOTING BAD JOINTS CIRCUIT BOARDS
PostPosted: Jan Fri 25, 2019 7:35 am 
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Freeze spray ! Great for smoking out intermittents.
Mark Oppat


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 Post subject: Re: TROUBLE SHOOTING BAD JOINTS CIRCUIT BOARDS
PostPosted: Jan Fri 25, 2019 4:03 pm 
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Location: S. Dartmouth MA 02748-1225 USA
oldradioparts wrote:
Freeze spray ! Great for smoking out intermittents.
Mark Oppat
Yeppers! Makes a frostline at the crack!

Not tools that any "normal" tech would have:

Vortac circuit cooler, uses compressed air to make cold air stream...

Ultra small heat gun, has silicone rubber nozzle to direct heat onto suspect parts..

Chas

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 Post subject: Re: TROUBLE SHOOTING BAD JOINTS CIRCUIT BOARDS
PostPosted: Jan Sun 27, 2019 4:48 pm 
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When looking for intermittent mechanical causes of electronic problems I sometimes use a custom-built spot vibrator. I also use thermal cycling as mentioned upstream.

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 Post subject: Re: TROUBLE SHOOTING BAD JOINTS CIRCUIT BOARDS
PostPosted: Mar Wed 06, 2019 7:22 am 
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I am given to understand that a UV light aka Black Light, helps too. Shine it on the board and supposedly cracks and bad solder joints will show up.

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 Post subject: Re: TROUBLE SHOOTING BAD JOINTS CIRCUIT BOARDS
PostPosted: Mar Tue 19, 2019 7:28 pm 
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I sometimes just rework the solder joints in the area of interest where the problem seems to be. One thing is where they snip the leads too close and cut off part of the solder blob with a flush cutter. Those can result in bad solder junctions. Reflow with new solder.

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 Post subject: Re: TROUBLE SHOOTING BAD JOINTS CIRCUIT BOARDS
PostPosted: Jun Mon 17, 2019 3:55 am 
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Best to remove solder first before clipping wire leads to component's if its on a circuit board. That takes the strain off the connection or hole because clipping introduces stress forces.

Its always best to clean up by removing solder also on old parts connector strips, especially if the wires or parts leads were wrapped around the lugs.
Most bad joints will look frosty in appearance, indicating the part was still moving when the solder was in the stage of going from a liquid state to a solid. That's called a cold solder joint.
Of you find solder on a connection that doesn't look like its wetted to the metal, it to is a bad solder joint. sometimes a connection will not allow the solder to wet and that's because of corrosion or dirt or grease or oil. ( I would even suspect cigarette smoke).

Most metals have a copper base and allow solder to weld into the metal. If not it may be a stainless or aluminum. Iron and steel metals will solder but have to be cleaned first and flux applied to cover the metal as when heat is applied it will corrode almost immediately, that's where the flux is important as it will prevent oxidizers from forming due to a lack of oxygen on the surface, and another benefit of flux is it will transfer heat while it is in its liquid state.

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