A KLH 21 FM Receiver (2009)

I dug back through the AudioKarma archives to get this gem. The radio is now with my parents. My niece loves turning the knobs to make the radio do ‘funny’ things. If all goes well we’ll be listening to ‘Alice’s Restaurant’ during Thanksgiving dinner this year.

This is a very incomplete write-up, from before I cared to write these things and just wanted to get on with it. If you have any questions, please ask.


I got this at the Westford MA Radio Fair this year. And I paid too much for it, as usual. After a couple hours of use, one of the knobs cracked off; a poor repair job by the former owner failed. So disappointed.

By summer, I got fed up with the polyurethane somebody slathered on. I wanted this radio to be just like the one I remember from my favorite old book store, with a resident cat patrolling the stacks and classical music from this Cambridge-made gem. So, I stripped it back to the veneer. I applied a Walnut Danish Oil to lightly stain back from the slight bleaching of the stripping process, then Tung Oil to finish, polishing with 0000 steel wool, then a couple applications of finishing wax. I’m happy.

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Nearly complete KLH 21 – waiting to push those fragile knobs on for later

The original and grungy plastic grill cloth had shrunken over the years. I could clean it but a noticeable gap would always be there. It looked ugly. I ripped the cloth off the Masonite front panel, and replaced with an open monks-cloth from JoAnne Fabrics. It was expensive, $10/yd.

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Application of monks-cloth on KLH 21 front panel board

Of course, you have to accept some things to use the stuff; It ain’t the original cloth; and cloth is a loose term for the original material. The threads in the original was a white PVC-like monofilament, woven in the same fashion of monks cloth, but with the occasional wide noodle-like white thread and yellow thin thread. Perhaps it went: white noodle – yellow – white – white – yellow – white noodle…

Anyway, I accepted the ramifications of this less acoustically transparent fabric material in exchange for the VERY nice look of it. I put down a single thin coating of spray-on contact adhesive (not Super 77, too thick and gummy) to attach. To protect it from being so easily stained and warped, I sprayed it with a clear uv/resistant varnish. I dabbed woodworking glue around the edges of the Masonite panel to reinforce the cut edges; a little glue in the hole edges made cutting them out worry-free.

The cloth I used gives slightly more resistance to airflow than the original PVC cloth, and while I’m not sure how much this will impact speaker frequency response, I cannot say it won’t. It is also all cotton, and if you leave it unprotected and touch it with dirty hands, you’ve now got an essentially permanent stain. (ed. – Three nieces and seven years later, no stains yet…) The overspray of varnish helps to stiffen and set the cloth and help protect the surface.

With all of that said, don’t it look pretty?

Because I’d like to use the radio 24/7 (music for the bird room), I recapped it completely and replaced the rectifier diodes.

In this original write-up, I left out MANY details. Here they are:

I completely left out how annoying working on this was is; KLH equipment always seemed to exchange serviceability for look and size. Look at the PCB, IF strip and tuner section. Each one needed to be removed to get proper access to it. The boxes were soldered shut, and PCBs mounted in the most inconvenient way. The main filter can replacement and the alignment was easy however. This is still nothing compared to how bad restoring the KLH 18 FM tuner is.

The knobs? They were all cracked and nearly falling off. I wonder if the combination of UV exposure, chemical composition of the plastic and the compression clip retention design makes the knob susceptable to this failure mode. Anyway, I went on eBay to buy a parts unit from a similar KLH FM/Turntable unit for the replacement knobs.

I also left out the process of refreshing the rubber on the rubber-coated fabric surround on the speaker with Permatex Black Rubber sealant. I also replaced the foam gasketing along the front and pack panels. Because the case acts like a traditional acoustic suspension enclosure for the single speaker, some degree of air sealing is needed for best effect from the speaker.

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KLH 21 Out of Case for Alignment
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Front View of KLH 21 without front cover, re-‘gummed’ speaker

Since those replacement knobs are still so fragile, I held off from pushing them on until I was completely  done working on the radio. Alignment was completed with no issues. I did such a nice job, my girlfriend thought it was way too nice to abandon in the bird room. So, it shall be a gift to my parents for the formal living room.

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All done – ready to play

Would you like see a master’s work on this radio? See Phil Nelson’s KLH 21 here. Enjoy!

An Autronic Single Paddle Morse Key (2016-17)

I have been solely a single paddle key guy, and was taken with the look of the Autronic after looking to upgrade from my current key. But with the positive reviews, they now can go for quite a bit. I searched around – and found this small heritage vegetable seed company selling one of these keys, with the nice looking conical lock nuts. BUT – it was missing one of the contact posts entirely, as well as both of the springs. Eh, I think I can find somebody to help.

Here is what we are starting with.

But why is a seed company selling a key? The seller said this:

The history of the key is it was my Grandfather’s.  He served in the Navy many years ago.  He passed away in 1982.  My parents inherited the estate and this was part of all the stuff.  I just recently was given a bunch of items from moving my parents to a new location and the items I didn’t have a need for or sentimental attachment to , I put online.  So the missing parts, sorry to say, are long gone after all these years and moves.  I sure with your skills you will get back in top notch shape!

The package finally arrived, and after clearing off dinner from the table, took my new key to pieces and looked at what we had to work with.

We are missing parts these parts: contact post, contact screw, 2x plastic washers, 2x springs. Everything else looks nice; the plastic paddle finger pieces are in good shape, as is the paint on the cast aluminum base. Even the rubber feet are still sticky enough to keep from sliding around my stainless steel table. The bones here are good but some work is needed.

My original idea was to buy some similar parts and adapt them as needed. I would have the plastic washers 3D printed. While looking for those parts, I found the website of 2BRadioParts.com (Donnie WA9TGT). Since his original work supporting the Drake radios, he has moved onto the fabrication of MANY replacement parts for bugs and keys, including replacement finger pieces for the Autronic. So, I wrote him an email.

To my surprise, Donnie offered to perform a restoration. He had a similar Autronic to compare to.

His plan was to:

1. Fabricate TWO new contact posts and conical lock nut from 6061 aluminum
2. Fabricate a new pair of plastic washers. The two original ones would be placed ‘top side’ and these new ones below.
3. Convert a stainless steel screw into a replacement contact screw
4. Find similar springs and modify into replacements of the correct length and end tapers, modelled from his own key

Surprisingly, he was already mostly done in just two days!

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Autronic Key Restoration In Progress

My key on the left, his on the right. You can see the conical lock nut in progress in the center. The springs and contact posts are new. In a couple more days, it is all done and ready to ship.

The replacement contact screw is machined from a 6-40 stainless screw, with the same flat notch that all of the other screws.

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Replacement Contact Screw

And here it is, all done…

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What do the 2 adjusters that stick out from AUTRONIC labelled part do? They do different things. Its an interesting mechanism, using a center paddle arm and asymmetric yoke to produce the required self-centering without limiting the adjustability for dit and dah motions. Besides what you can see in the image, the top left side adjuster is a centering adjustment and the top right side is the dit spring force.

The patent and drawing may help: https://www.google.com/patents/US3098898

Here is a quick video of the key’s unique adjustment mechanism.

What remains to be done is to add a cable that will match how nice this looks. What would be really nice is some super-flexible stuff that will lay flat on the desk and matches the grey of the cast base. Maybe something like EcoFlex, or a fabric braided cable used for audio. I have some digging around to do. So, more to come.

Update Sept. 2017: I found a braided-jacket 1/8″ TRS audio cable from my local electronics store, with a grey tone that matches the wrinkle paint.

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This was my first project working as ‘project manager’ – I did some stuff but when it comes to the details, finding the right person with the skills, experience and tooling made all the difference.  This was made possible by the fantastic work of WA9TGT. Donnie is the man! At least from his website, restoration isn’t main business – he usually make up parts and replacement finger pieces for many keys – but when he does it, it is done VERY well. Be sure to check him out.


Thanks to Charlie WA2ONH, here are some related links:

Autronic Paddle

Later Autronic Ad for “Perfect Code”

N2FQ Autronic Cleaning Video