The page describes modifying the circuitry of a camera, the risk of doing this is all yours, do not attempt this if you're not proficient at electronics.
Do you still use Panasonic's F15 cameras from 1991, and want to bring return video to the camera, but don't have all the parts you need? This page details how to manage it.
The camera has various ways of implementing line view (viewing a return video signal to the camera), each of them for different modes.
When you have the WV-AD37 RCU back on, a video signal can be fed back to the camera from the RCU, and a switch on the lens lets you switch the viewfinder over to view that signal instead of the camera. Of course, for those without those two accessories, it's next to impossible to see a return video signal in the viewfinder, for program production purposes (e.g. lining up a shot to fit into a video effect). With the RCU back end, but without the RCU, you could modify the back end to add a video input socket. Likewise with the WV-AD36 genlock back (you could modify it).
When cabled to a 10-pin VTR, through the VTR connector, the viewfinder will automatically show the VTR signal when the tape is played back. The 10-pin video line is bi-directional, either the camera signal goes out of it, or the playback signal back into it. This is no good to us, because you'd have to jury-rig a DC-biased signal to go into the camera, and power the camera from the 10-pin socket (as the power switch is also the mode switch), which would preclude the use of a genlock back on the camera (necessary for analogue video mixing), as that only works when powered directly (through it's own 4-pin or 10-pin sockets). And, of course, you want to view the line-view signal while the camera is still sending its own video out.
When cabled to a 14-pin VTR, one of the pins can bring a signal back, and pressing a button on the camera body will display it in the view finder. The camera has to be powered from that connector, too, to run in that mode. There's one switch for selecting the 14-pin mode, and it also selects the power source. This precludes the use of a genlock back, as it will only work (fully) when powered through itself.
The WV-AD36 genlock back doesn't provide any way to feed in a return video signal. Its 10-pin connector only handles power, camera video, genlock, and audio (NB: a camera is usually not a good source for getting audio for a multi-camera production). It really should have had line-view in there, but they didn't bother, even though there are unused pins in the connector, and the line view buffer circuitry is on the circuit board.
However, you can modify the back to bring in a video signal. You need to add a socket somehow (not easy, as there's not much room, and the genlock back is mostly thin plastic), or modify the 10-pin to re-use a couple of its pins for another use (e.g. remove the useless audio, and use those pins, instead), since the unused pins aren't actually present in the connector (they left empty holes in the plugs). Take video from your newly arranged socket, and connect it to pin 2 on connector 12, and join its ground to another video socket's ground. Connector 12 is the four pin socket in the middle of the edge of the board, next to the ribbon connections. It only has two of the four pins in use, pin 2 is the one nearest the ground wire. This will give you a working line view.
As an alternative, you could modify the viewfinder. Interupt the video wire leading to the monitor's video input (either in the monitor, or in the interface box between the camera head and the monitor), insert a SPDT switch to changeover between feeding the camera's signal to the viewfinder, or feeding a signal from an external socket to the viewfinder. Put a 75Ω resistor across the external video socket.
This would have the advantage that you could simply use one BNC cable from the camera for video out; another to the camera, for genlock; and another to the viewfinder, for line-view; without needing any special types of cabling, at all. Although it's more work to connect a camera (patching three cables, and working out which one is which), you won't need any expensive and hard to get multicores.
I did a modification based on the first approach: I removed the plastic 10-pin connector (that only has 8 pins actually present), and replaced it with a 10-pin CCJ plug as used on 1970s/1980s video cameras. Fortunately, these will fit through the hole left by the original connector, with a bit of careful persuasion. Being lucky enough to have some plugs with locking rings on them, rather than having locking rings that fitted between the plug and cable backshell, I could avoid having to use a socket (which would have left exposed pins with voltages on them if the cable was unplugged), and fit a plug to the camera. This meant that I could re-use our old camera cables between the camera and the other equipment, and without having to rewire the cables, as they have sufficient wiring on the right pins to handle everything. And unlike many camera cables, these cables are generally set up with a plug at one end, and a socket at the other, so you can extend cables by plugging them into each other (as you'd do with XLR leads). Now, only one lead goes between the camera and everything else, rather than a bundle of leads loomed together.
For once, life is made easy. Every CCJ plug and socket that I've ever seen has the pins numbered on them.
The asterisk marked pins are different than the original 10-pin wiring on the WV-AD36 back end. They're omitted on the original wiring, and there's no information suggesting that they would have been used for anything. The 10-pin plug on the side of the camera is wired differently, yet again.
We have a small patch lead that goes out of an (extra installed) socket on the back end, connecting to the box on the viewfinder mounting bracket, where we've installed an interface for the tally lights.
We, also, opted to break the audio line out to a separate socket. There's little point in taking audio from the camera, the quality isn't that great, and it's usually not a good location to take sound from, anyway. So we can, now, use it for an intercom line.
NB: The “RET” (return video) button on the camera head, below the lens, only functions when the camera is connected through one of the VTR connectors, and in in the VTR mode. It's useless to us.
Be very careful not to break the locating pins on the plugs and sockets, that only allow you plug them together the right way around. Without the pin, the plug can be inserted upside down, and supply reversed power to the camera, and damage it. The camera has no real protection against reversed power.
Warning: Because there's a plethora of variations on how different cameras use the 10-pin plug, you should only ever connect equipment together that you know will work together.