Cleaning "rosin" off a circuit board ?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by benabloom, Jul 11, 2008.

  1. benabloom

    benabloom Member

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    Hi there,

    I recently modded a Valve Junior head. When soldering some components to the board, a slight pool of hardened rosin (not solder) is visable around the solder site. In some cases , that hardened rosin crosses a trace.

    My question is do I need to remove the goo ? If so how ? I am afraid to scrape it off because of damaging the circuit board. Is it conductive ?

    The solder itself is not crossing any traces (I checked with a magnifying glass)

    Thanks,

    Ben
     
  2. Lyle Caldwell

    Lyle Caldwell Member

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    You don't have to remove it, but acetone (nail polish remover) removes it easily.
     
  3. John Coloccia

    John Coloccia Cold Supporting Member

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    What he said :)

    I personally use Q-tips for stuff like this to keep from accidentally nicking a trace.
     
  4. benabloom

    benabloom Member

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    Sweet ! Acetone it is! Im gonna clean it off because it makes my soldering look uglier than it is and I don't need any help with that:)

    but 1st Im bout to fire it up to test it.

    -B
     
  5. SatelliteAmps

    SatelliteAmps Member

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    I like alcohol for cleaning.
     
  6. stratman_el84

    stratman_el84 Member

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    +1 on the alcohol for flux removal. Especially when talking about a repair to a production amp that may have plastic components that may be damaged by stronger "flux-remover" type sprays containing stronger solvents. I keep several small paintbrushes and toothbrushes around just for that purpose.

    Cheers!

    Strat
     
  7. alltone

    alltone Member

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    As mentioned I would advise NOT using acetone as it will dissolve the coating on the board and any plastic parts. Alcohol or methyl hydrate 100%.. and a soft bristled toothbrush.
     
  8. Lyle Caldwell

    Lyle Caldwell Member

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    I've never had a problem with acetone, though I certainly don't pour it on. But alcohol works too.
     
  9. Nolatone Ampworks

    Nolatone Ampworks Silver Supporting Member

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    That resin is flux, which is in the core of most solder. It will splatter around the work and if left there can attract dirt, etc. Really not a *functional* problem for tube amp circuits, but can be a problem for more delicate circuits that are more tightly populated.

    I see little splatters of flux in even high end boutique amps, but if there's a "blob", it needs to be cleaned up, for aesthetics if nothing else.

    Alcohol is the "milspec" approach, at least that's what we were trained to use in the good ole USN.

    Here's what I do and it works great. Get two acid brushes (little mettle tube brushes with thin bristles, you can buy them by the bag at your local hobby or craft store).

    Leave one as is, take the other and trim the bristles down low so they are stiff.

    Swab the area with alcohol using the long bristle brush. Let the alcohol break up the flux a bit (but not TOO long, it will evaporate quickly), then scrub the spot with the stiff brush. You may need to repeat. At end, swab it again with alcohol and blot with a napkin (we used to use "Kimwipes", like a stiff tissue) to clear the residue.

    I'm sure other suggestions work as well, just offering mine which Uncle Sam consideres good enough for F/A18's pulling 8 G's :)
     
  10. benabloom

    benabloom Member

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    Thank you all!
    l'll use Alchohol.... !
     
  11. Mickey Shane

    Mickey Shane apolitical Silver Supporting Member

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    Try water first. Many modern fluxes are water soluble. I've been using that kind since '95, at least.
     

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