I have some catching up to do in terms of the full story here so this time I’ll start with the bottom line, a fully working radio.

The KY-67 was designed as a super heavy duty 30-76 MHz FM military pack set with built in encryption.  Since encryption devices are not allowed to be surplussed out, the crypto boards have been removed from all of these radios which made it out.  Unfortunately, for a number of reasons hardware and software, the radio will not operate as a regular radio without those cards.

I read out the microprocessor code and after disassembly was able to patch the code to allow it to run without the crypto cards present.  Removal of a FET allowed the processor to run with missing hardware.

The last part was that both receive and transmit audio go through the missing cards.  To solve that I had to build equivalent circuitry.  Here is a picture of the top of the card I made:

Here is the bottom:

And here it is in the radio:

With this done (and a few jumpers on the backplane) the radio operates as it should.  Volume, squelch and squelch disable all work as intended.  Those functions and both transmit and receive audio amps and filtering are on the new card.

Oh, and one more fun thing:  another very smart engineer joined me later on in this project (very pleased to meet an engineer of that caliber!) and located in the code where it could be patched to extend the low frequency limit from 30 to 28 MHz.  So now the radio will do FM on 10 meters as well as 6!