Codan 8727 info?

VK3ZYZ

Moderator
Does anyone have a service manual or even just a circuit for a Codan 8727 set?
I am getting one of these going again. It had broken switches on the front, and I have changed the mic connection to a 4 pin "standard", not the Codan 7 pin version.
After I get it working again, the next step will be to change to the VFO in place of the crystals.
I will post more info of the progress as it goes on.
 

VK3ZNA

New member
Does anyone have a service manual or even just a circuit for a Codan 8727 set?
I am getting one of these going again. It had broken switches on the front, and I have changed the mic connection to a 4 pin "standard", not the Codan 7 pin version.
After I get it working again, the next step will be to change to the VFO in place of the crystals.
I will post more info of the progress as it goes on.
The Codan 8727 is a crystal locked version of the Codan 8528 radio.
Geoff VK3ZNA
 

VK3ZYZ

Moderator
Codan8727_TestVFO_01.jpg
I am still battling with this one, but here is the set with the test VFO running it.
No mic TX yet, but otherwise ok.
 

VK3ZYZ

Moderator
The receiver ran very well on tonight's 80M sked. And I actually did a tx test with whatever managed to squeeze through and it worked but quite distorted and very low power. When switching to Tune, it outputs plenty of power.
I am still baffled as to what is stopping the tx running with the mic.
 

BillC

Active member
Also if there is a Tx / Rx c/o relay there might be diode in series with the PTT, a polarity protection diode in that position could protect the whole Tx stage from reverse polarity, if the diode was OC there would be no PTT function .??
 

VK3ZYZ

Moderator
I have put some code into an Arduino VFO and am in the process of growing it into the Codan 8727.
Codan8727BandSelect2.jpg
A resistive network is connected to the band switch and now selects the band on the Arduino.

Codan8727BandSelect1.jpg
This also shows the coax feeding the VFO in.
Later, I will clean all this up, but for now, it is just a quick test setup.

I'm pleased that my spreadsheet worked out well.
A few of the values had to be made from a couple of resistors as I did not have them but I think they are all standard 1% resistor values anyway.
BandResistors.png
BandResistorsODS.png
 

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VK3ZYZ

Moderator
The 8727 now has the OLED display installed (on a slant).
The code below will compile for OLED or LCD as desired.
For a 2x16 LCD, change the line....

// comment out line below for LCD
#define USE_OLED
to
// comment out line below for LCD
// #define USE_OLED

Now that this code is working well, I may start on the 7727 set and see if I can make that one transmit correctly.

Front20210725_01.jpg
The red film is matt, and it would be better to just be clear red.
OLED_Matt_film.jpg
 

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