Sony DXF-3 Viewfinder

An interesting aspect of older analog video cameras is that the earliest iterations of the viewfinder used very small CRT displays, just as more modern cameras use small LCDs. Because of the fact that an analog viewfinder module would need to contain an entire mineaturized CRT television, they were often detachable in order to make the camera more portable.

Analog video cameras can be readily found in surplus stores and thrift shops, though often in semi-functional condition. The side effect of this is that it becomes relatively cheap to acquire these types of mineature CRT modules.

Furthermore, it's quite easy to interface with them, as their connection to the main camera will typically consist of a supply voltage and a composite video signal, meaning that a composite video signal can be directly fed to the display once the pinout is identified.

Above are the labels on the Sony DXF-3 Electronic Viewfinder. This particular unit was manufactured in July of 1983, which makes this year its fortieth birthday!

The Sony DXF-3 has eight fasteners; four on the rear (seen at right), and two on each face (seen at left). The rear screws must be removed first, followed by those on the sides - though only one side needs to be removed for a decent look at the electronics.

Above, the interior of the Sony DXF-3 can be seen. It is indeed just a mineature CRT television, albiet designed to run off of 12 volts DC. The top board includes the boost converter and flyback circuitry, and the bottom board contains the analog electronics that receive the composite video signal.

From this angle, the screen can be seen, along with a few indicator LEDs. Because the display sits perpendicular to the user, a mirror can also be seen positioned at fourty-five degrees.

Also visible at this angle is the solder side of the PCBs, allowing the wire harness connections to be traced in order to determine its pinout. This gives us the following pinout:

RED - Composite Signal
YELLOW - Composite Ground
BROWN - 12VDC Supply
BLACK - 12VDC Ground

With the pinout, I was able to make the following adapter with a barrel jack connector and BNC connector, to make powering and connecting to the display easier. The device originally used a U-style eight pin DIN connector, which I removed early on in favor of a JST connector.

Of note is that there are four other wires (white, gray, blue, and orange), three of which control the indicator lights built into the viewfinder, positioned around the display:

GRAY - "BATT"
BLUE - "REC/WB/TALLY"
WHITE - "LOW LIGHT"