[R-390] What is on the 390 chassis anyway

[Norman Ryan via R-390]

Hi,
The link also has detailed restoration tips on the R-390A, SP-600,  ART-13, etc.  -- all well worth bookmarking.
Thanks for sharing this!

73,Norman
 

     On Monday, October 13, 2014 11:32 AM, Bill Guyger via R-390 <r-390 at mailman.qth.net> wrote:
   
 

 Hi All

Tisha as usual is dead on about the coatings and what not to do. If you totally remove the Chromate / Alodine / trade name of the moment coating the aluminum will begin to oxidize and the chassis is the ground return..... .......kind of important. Especially important if you take the radio down to bare metal and clean the mating areas between the various sub panels which is what should be done if you are totally rebuilding a 390A because vibration will have had its little say over the last 50 years or so and loosened some of the hardware connections.  

FWIW Henry Rogers at http://www.radioblvd.com/ on his ART-13 page has a recipe for simulating the MFP coating using paint available at art supply places.

Bill AD5OL
  


On Monday, October 13, 2014 7:54 AM, Tisha Hayes <tisha.hayes at gmail.com> wrote:
  


The yellowish tinge of the aluminum can come from a couple of things;

1. It can be MFP (moisture and fungus protectant); a type of varnish.
Usually you will see it coating lots of things and not just the aluminum.

2. It can be aluminum yellow chromate. This is a electrolytic treatment
that was done to many aluminum items in the military and avionics
industries. It is no longer available as it used "hexavalent chromium" to
create the coating. It "passivates" the aluminum, sort of like a controlled
corrosion up front to keep uncontrolled corrosion from setting in later. It
has a golden look to it. The original process was toxic as hell and is no
longer possible using the same technique.

3. It can be fifty years of cigarette smoke residue.

409 spray cleaner will not remove MFP or aluminum yellow chromate, it will
cut through dirt and cigarette smoke residue.

If you get aggressive with solvents you can remove the MFP. If you get
aggressive with abrasives you can remove the passivated layer of aluminum
yellow chromate. You really do not want to take the radio all the way down
to bare, shiny aluminum unless you plan on waxing, varnishing or painting
it again.

I have succeeded in restoring the MFP and the yellow chromate look with
spray varnish. It (mostly) looks the same and provides at least some
corrosion resistance.

If you are re-finishing aluminum front panels you probably need to primer
the aluminum of you used stripper or a mechanical means to take it down to
shiny metal.

-- 
Ms. Tisha Hayes. AA4HA

*""It is not because things are difficult that we dare not venture. It is
because we dare not venture that they are difficult." -Seneca"*
______________________________________________________________
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
______________________________________________________________
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