Codan 8525B Arduino Si5351 VFO

VK3ZYZ

Moderator
ModdedFront.png
I have the Codan 8525B running with full frequency selection now. It is making use of the original front panel buttons. I'm pretty pleased with it!

After failing to drive the existing PLLs, and popping part of one somehow, I went with an Arduino Nano driving an Si5351 triple digital VFO board.
The Arduino Nano and Si5351 are mounted on a board that replaces the original front.
CodanVFO.jpg

As mentioned above, my attempts to drive the original PLLs was less than satisfactory, so they have been disabled, then the Si5351 board is used to generate the first mixer, second mixer and side-band frequencies.
To limit the mods to be fully reversible, the front is just the same, with a white .9" OLED display in the place where the 2 digit LED was. Also, each original VCO has a short from the gate to gnd to disable them, and the coupling resistor was cut at the VFO end and now has the Si5351 signals coupled to the cut resistor end with a 10nF cap instead.
There is one cut on the main PCB to disable the original USB/LSB signals.
All theses mods can be reversed quite well if needed.
I have not made use of the call tone option, and it was removed as the proto version was installed in that place. But there is no reason why it could not be incorporated if wanted.
The nano is up to 90% full, and I am looking into using a Teensy or Nucleo board that has the same pin out as the nano. Level shifters from 3.3V to 5V will be needed then.

This is a work in progress.

For those interested in more info, the files are below...
 

Attachments

VK3YNV

Moderator
Looks great, congratulations on a very neat conversion. That Oled display fits perfectly, it looks like it was made to go there!
 
Last edited:

VK3ZYZ

Moderator
As mentioned in my post about trying to drive the PLLs directly, that option has been abandoned for now.
This is the next Codan 8525A mod. Similar to the earlier 8525B one shown above, but a slot was cut in the box side and the tab bent down to solder the coax onto.
VFO_Mod1.JPG

Here is the coax connected.
FirstVFO.JPG

Second VFO likewise...
SEcondVFO.JPG
OneLidOn.JPG

This Time, I have disconnected the +5V to most of the chips on board..
Disconnect5V.JPG
then added a choke to feed the couple of logic chips still needed...
5VToIC9.JPG

Finally, the Si5351 board is mounted on the radio, not on the controller PCB.
Si5351.JPG

That aim is to port the 8525B code to the 8525A, and also use the "VFO Delux" ESP32 board in place of the Arduino Nano.
I will update this as I work it out.
 
Last edited:
Top