Strange soldering issue which I thought was component problem

[mitutekh]

I had a crappy signal when building a mammoth fuzz clone - with the noise gate turned all the way down I just couldn't get rid of this screaming noise that sounded like a motorbike (pretty cool sound but NOT what I wanted for this pedal). Thta was with the fuzz on lowest setting

I took the homemade circuit board back to my testing breakout box and same problem - I tried replacing a couple of components I thought pehaps I had fried during soldering and the same problem persisted.

The last straw before rebuilding the whole board was to go over my solder joints as I noticed they seemed quite dull looking. Hey presto - I hooked it up and everything worked great (like the one I had made for my missus a couple of weeks previous)

My question is - can the dull looking solder joints cause this issue or am i just going mad? never had this problem before when ive wired guitars...

[theundeadelvis]

Dull solder joints can be an indicator of a "cold" solder joint. They can definitely cause issues.

[familyortiz]

Although most solders have a core of flux, I still like to apply a bit of flux to some solder joints, followed by a good cleaning of course.

[mitutekh]

I agree with you on the flux - just makes it easier - i think my problem may have been that i used too much flux and didnt clean it off fully before testing. everythings working now though thankfully

[Le québécois]

followed by a good cleaning of course.

and what product should we used to do that?

thx

[familyortiz]

Most off the shelf flux removers are good but high purity isopropyl alcohol does a great job.

[col]

The lead free solder which is all I can get now forms very dull joints when compared to the solder I used to use but the joints seem just as strong. Check on 'motorboating' on this forum it sounds like that might be your issue.

[amptramp]

Most off the shelf flux removers are good but high purity isopropyl alcohol does a great job.

Isopropanol (which is isopropyl alcohol) was the standard flux cleaner for spacecraft and military circuit boards. Spacecraft soldering was done to NASA NHB5300.4.  Military was to IPC-610.  The NASA spec tries to minimize the solder used since solder is heavy.  At one time, the component reliability man called me over to take a look at a board and give him my impression.  I said it looked like not enough solder and it was all cold joints.  Then he said, "Check it out with this eye loupe.  This is the best soldering you will ever see."  I checked it out.  There was a solder meniscus going halfway up the thickness dimension of the flatpack surface-mount leads, exactly as specified.  All joints were good.  And now, 36 years later, he was still right - it is still the best soldering I have ever seen.