Antique Radio Diary: Restoring the RCA 86K7

The Saga of the Broken Band Indicator Flag Bracket.

Today I "patched" that broken band flag bracket. I hesitate to say I "fixed" it, though I guess it is fixed in the same way duct tape "fixes" a leaky boat, but for now it works.

The band switch indicator flag is a large piece of plastic mounted to a bracket which is in turn mounted to the shaft of a rotary switch and secured by means of 2 set screws.

Somehow it was broken (though I've heard this is a common problem with this type of radio), but after removing it and taking a good look I can see how it happened.

The bracket was made of some kind of cheap white metal and was replete with cracks even in places where there was no tension applied to the bracket. Perhaps 80 years of thermal changes was just too much for it, I don't know.

Special thanks to Chas at ARF for the engineers drawing of this bracket and for permission to post it here.

To see this drawing full size, or any image posted here, just click on the image.

The "Fix"

The "fix", or really the "Patch" was a home-brewed, southern engineered job. Since the flag was simply screwed into the bracket this made life considerably easier.

What I scrounged up was an old phenolic knob with a set screw and a plastic tray divider from an old screw/bolt drawer organizer.

I cut the plastic divider down and sanded it to a similar shape, then drilled it out where all the hardware would mount. Since the holes where the flag attached were threaded, I used those screws to thread the plastic part.

The phenolic knob was a pure stroke of luck, again one of those things that Hollywood would never buy in a million years. Not only did it have the set screw I needed, but it also had three little screws inside that held an indicator apron on to the knob.

I removed the indicator apron and cut the shaft of the knob from the grip making a nice smooth shaft. I then sanded it down to a dimension that would fit properly between the flag bracket and the tuning shaft. What I ended up with was a "collar" only slightly wider than the hole for the retaining screw.

I then used the screws, and associated holes, from the apron to attach the divider to which I had already attached the flag to.

And just like that, Bob's your uncle mate!

The fit is just a little tight when switching from Medium wave to Broadcast and the metal part of the flag contacting the tension pulley for the tuners idler belt makes the most satisfying metallic "Clunk!"

Update - October 28, 2013

I sent the technical drawing (the one pictured on this page) to a good friend of mine who is a professional machinist in Dayton Ohio, and he made up a new band selector flag bracket for me out of a piece of aluminum he had in the scrap pile. He did an absolutely fantastic job just from the drawing alone.

My apologies for photographing it upside-down (blush).

I had planned to send him the original part to work from also, but since I finished up this project about 7 years ago, the original bracket has literally reduced it's-self to little more than dust.

Here's a few pics of the new part going in :)