[R-390] [GreenKeys] Removing MFP (fwd)

[Curt]

If it is phenolic-based varnish it would most likely come off with 
methylene-chloride.   MEK might also work.

Curt



On 3/26/2012 10:25 AM, Nick England wrote:
> You just need a bottle of "suitable solvent" -
>
> SIMCO http://www.simcocoatings.com/t-838.html says:
> Solvent Type: Xylene/Aromatic/Aliphatic Hydrocarbon
>
> Army Technical Manuals usually say remove MFP varnish by scraping with
> a knife blade (for a small area) or using trichloroethylene as a
> solvent for larger areas.
>
> A study of MFP removal for circuit board repair tried 28 solvents as
> chemical strippers, of which about 50% worked.
> www.dtic.mil/dtic/tr/fulltext/u2/283476.pdf
> It also says a "cool" soldering iron 35-400 deg worked better than a
> "hot" 600 deg one at softening the varnish.
>
> Finally, any number of military manuals (including for the SP-600)
> talk about touching up the MFP afterwards, but never mention anything
> special for unsoldering.
>
> ======================
> The applicable document on MFP treatment seems to be:
> MIL-T-152B 31 March 1961
> SUPERSEDING MIL-T-152A 14 December 1955
> MILITARY SPECIFICATION - TREATMENT, MOISTURE- AND FUNGUS-RESISTANT. OF
> COMMUNICATIONS, ELECTRONIC, AND ASSOCIATED ELECTRICAL EQUIPMENT
>
> Which unhelpfully just says:
> "Resoldering of wire connections shall be made only after cleaning the ends of
> wires and terminals with a suitable solvent to remove old varnish."
>
> MIL-T-152B says to use:
> MIL-V-173 - Varnish. Moisture-and-Fungus-Resistant (for the Treatment of
> Communications, Electronic, and Associated Electrical Equipment).
>
> MIL-V-173C (1969) says:
> This specification covers one type of moisture-and-fungus-resistant
> varnish consisting of a para-phenyl phenol-formaldehyde resin in
> combination with tung oil and suitable solvents which has been made
> fungi static by the addition of 7.0 +/- 1 .0 percent salicylanilide or
> one percent copper 8-quinolinolate, for the treatment of assembled
> communications, electronic, and associated electrical equipment.
>
> 3.1.1 Volatile content. The volatile portion of the varnish shall be any
> suitable solvent or solvents: however, methanol (wood alcohol), benzene
> (benzol), chlorinated hydrocarbons, or other highly toxic solvents shall not
> be used.
>
> ========================================
>
> FWIW, A 2008 discussion on antique radio forum turned up the following comments:
> 1) "In WWII a mixture of Tung oil and copper Napthalate was used"
> 2) "In 1950's-60's aircraft -  a two part resin compound, and not easy
> to get off en mass. you can soak it in MEK or Acetone but probably not
> a good idea since that stuff will attack just about anything that
> isn't metal."
> 3) "Use a xacto knife or similar tool to get enough off to put a
> soldering iron on the bare solder joint. The MFP will then become very
> plyable and it can be easily cleaned off after removing the component
> or wire".
> 4) "I've always used Acetone to remove MFP before soldering."
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>