After recently purchasing a Robbe F14 Navy from a friend of mine, I wanted to do a dual analog / digital conversion, as I sail both boats and a submarine. Along with the radio came a Corona DIY conversion kit, which my friend had intended to install, but never got around to, the following is how I carried out my conversion, for anyone who wishes to do the same in the future.
The first photo, "F14 Navy Digital Conversion - Insides" shows the right hand side of the circuit board, this is the analog radio section, it is connected to the left hand side with four wire links, the first of which is a negative connection, this is a silver wire, at the front edge of the board, just to the left of the two capacitors, there is an identical one at the very back of the board as well. For this install I connected the digital module ground, (Brown wire) to the negative of the unused trainer socket, this is the brown wire connected to the board, just to the right of the word, "Train".
The second wire link in from the front edge of the board, which has been replaced with two yellow wires in the photo, is the PPM signal line, information travels from the left side of the board, to the right side to be transmitted, so the left hand of the two yellow wires in the photo, goes to the centre terminal of the DPDT selector switch.
The third wire link in from the front edge of the board, which has been replaced by two red wires in the photos, is battery power feeding the radio circuit, disrupting this feed and the signal ensures that the analog side is completely isolated when you are in digital mode.
So, with the left hand pair of signal and battery power wires connected to the centre terminals of a sub miniature DPDT switch, a pair of yellow and red ran back to the analog board and another pair, from the opposite side of the switch, are connected to the Corona unit.
Now, with both analog and digital receivers setup on the bench, with power and a servo, switching on the TX will, all being well, will drive one RX only, flicking the change over switch will then give control of the other RX, with no response from the other.