[R-390] EXT: Re: Painting Knobs

B Riches bill.riches at verizon.net
Sat Aug 17 17:39:53 EDT 2024


 Sorry to hear about the problems painting knobs.  In the 60 or so years that I have been restoring R-390A receivers here is my method.  Took a while to figure it out.  ymmv.
1. Obtain the following stuff.
a, From harbor freight - 54976 vibratory tumbler.  63672 fust cutting tumbler media.b From hobby lobby - Artist brush - size 0 silicone. Artist's Loft Titanium white acrylic paintc. From Ebay - old portable toy record player - manual - only has to rotate the player.d. Misc paper towels, Kleenex, #30 motor oil, Krylon primer/satin black spray paint and a small shop towel.
Procedure:
a. Remove setscrews from knobs.b Fill tumbler about 3/4 full of the green medium.c. dump 5 - 10 knobs in tumbler - submerge them and space evenly.  - leave room for them to move around.d. Run tumbler for about 2 hours - all paint will not come off but what is left is very thin and does not interfere with repaint.d  Use rubber gloves to handle knobs and wipe off dust using cloth wipes - no liquid.  Knobs will look strange.e. I make a drying rack using a 2 foot 2x4 with nails sticking up.
Knob Painting
a, Outside hook up your turntable - set to 45 rpm put a knot on it.  and turn it on.  Knob will rotate and this allows you to get an even coat on it.b Hold spray can about a foot away - closer you will get runs and too much paint on the knob. I don't move the can much - Start the turntable and spray at a 45 deg angle for three rpm - works for me. it will take many knobs until you get it wright.  Duds go back in the tumbler, and you start over! To remove knobs from turntable I use a fine point needle nose plier in the set screw hole to put it on the nail.  Let knobs dry for a week.
Now the fun part - painting the lines.
a. Put a paper towel and a Kleenex on your bench.b. Put a dab of paint  - lima bean size - on a small piece paper.c. Wet a small spot of water on the shop towel - this is to clean wet paint off of your hands.d. Put a drop or 2 of motor oil on the paper towel.e.The idea is to get as much of the paint in the slot and not over the place.  To keep paint going in the slot I gently only once pull the knob through the oil drop.  This coats either side of the slot and paint will not stick to it.f. Use the small brush - dip into the paint and as carefully paint the slot.  This will take a while to get it. usually one or 2 swipes.  Now very gently with the slot facing down - rub the knob on the Kleenex in one direction.   If you have a bit of paint outside of the slot, take a damp Q-Tip and try to remove the paint.  When you are good at it you should get 9 out of 10 good knobs.  If it is a real mess - clean out the paint from the slot with a dental           pick and toss the knob in the tumbler. 
Knobs are not easy.  I hope you can use some of these ideas
73,
Bill, WA2DVUCape May, NJ


    On Saturday, August 17, 2024 at 04:28:18 PM EDT, Cecil acuff <chacuff at gmail.com> wrote:  
 
 I’ve done this a few times and it works well for me.

I’ve had all the knobs glass bead blasted to strip them and provide a bit of “tooth” for the paint to adhere.

I have sprayed all knobs with Tempo brand marine Zinc Chromate primer.

Available at most boat dealers service shops.

I let that cure naturally for a couple weeks.  You will know when it’s cured as it will develop a feel that it’s no longer still drying.  A slick feel that indicates it cured.

 I then spray with my satin topcoat…Krylon or Rustoleum…your choice.

I let that cure for a couple weeks and you are good to go.

Very durable finish.

Cecil


Sent from my iPad

> On Aug 17, 2024, at 2:37 PM, Fisch, Michael <mfisch at kent.edu> wrote:
> 
> Hi,
> I had an old can of zinc primer I used when I redid my 390a 15 yeras ago.  It is by TEMPO and it was a marine paint, but they have others.
> Search tempo primer.  Or is it a different primer?
> 
> Michael Fisch
> AC8PD
> ________________________________
> From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on behalf of Jordan Arndt <Outposter30 at shaw.ca>
> Sent: Friday, August 16, 2024 4:53 PM
> To: Les Locklear <leslocklear at hotmail.com>; Jacques Fortin <jacques.f at videotron.ca>; 'Barry' <n4buq at knology.net>
> Cc: 'R-390 Mailing List' <r-390 at mailman.qth.net>
> Subject: EXT: Re: [R-390] Painting Knobs
> 
> Thanks for those posts guys...I thought I remembered that at least some of
> the knobs I had done in years gone by had yellow primer. It's whats on the
> inside of of the  frequency dial cover. IIRC...
> 
> FWIW, I had good luck with heating the knobs to ~300F before applying the
> primer, then checking for coverage voids and then baking the primer on at
> 300F for 30 minutes, then repeat for the color coat. I believe I used an
> automotive primer for zinc plated parts.
> 
> 73...Jordan VE6ZT
> 
> 
> ----- Original Message -----
> From: "Les Locklear" <leslocklear at hotmail.com>
> To: "Jacques Fortin" <jacques.f at videotron.ca>; "'Barry'" <n4buq at knology.net>
> Cc: "'R-390 Mailing List'" <r-390 at mailman.qth.net>
> Sent: Friday, August 16, 2024 1:36 PM
> Subject: Re: [R-390] Painting Knobs
> 
> 
> Like a lot of things, it has probably been banned. Many years ago, when I
> was a service manager for an automotive dealership we used it to combat
> corrosion problems on battery terminal posts. Clean them, spray with zinc
> chromate primer…end of problem. Most of the R-390’s I’ve seen have yellow
> ( zinc chromate primer) as a base for painted parts. The batteries these
> days don’t seem to have the same problems. Hey, I’m old this was over 50
> years ago in the early 70’s. I still have a rattle can of it. Does it work?
> I don’t have a clue or an R-390 series receiver anymore. I just read for
> memories from old friends.
> 
> Les Locklear
> 
> Sent from my iPad
> ________________________________
> From: Jacques Fortin <jacques.f at videotron.ca>
> Sent: Friday, August 16, 2024 2:25:23 PM
> To: 'Les Locklear' <leslocklear at hotmail.com>; 'Barry' <n4buq at knology.net>
> Cc: 'R-390 Mailing List' <r-390 at mailman.qth.net>
> Subject: RE: [R-390] Painting Knobs
> 
> Yep, it was the name of the yellow stuff that can be found years ago.
> Does not seems to be available anymore on this side of the border however...
> 
> 73, Jacques, VE2JFE in Montreal
> 
> Zinc Chromate Primer. It's available in rattle cans.
> Les Locklear
> 
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