FiveFish Audio's Oscilloscope Add-On Turns a CRT-Based Scope Into a Fully-Functional Video Display

FiveFish Audio has released an oscilloscope add-on with a difference: The board lets you hook in any standard composite video source and use your scope as a monitor for video playback.

"I've seen other people demo movies/videos playing on their oscilloscope display, and it seems a mystery how they do it, and I can't find anyone that sells ready-made PCBs or kits either," FiveFish explains of the reason behind the unusual add-on. "An online friend recommended I look into a Video Sync chip, and also found plans on the Internet and tried them out on a breadboard but wasn't happy with it. The horizontal and vertical frame was distorted due to the use of a simple RC circuit. So I tried improve on it incrementally until after several hours of experimentation, and a couple of PCB prototypes later, I have this working."

"All parts are common and jelly bean variety so you can probably build this using parts in your junk bin or in your assortment kit. The only thing unique is the Video Sync Converter chip. The rest are just general-purpose NPN and PNP transistors, an NE5532 opamp chip (for 9V operation) or an OPA2350 opamp chip (high-speed, 5V operation). I will include the yellow RCA jack with the PCB."

The board, which is provided as a bare PCB with no components other than an RCA jack for video and a DC jack for power, is only compatible with oscilloscopes featuring an XY-mode and a Z-axis input — and it needs a classic cathode-ray tube (CRT) display, not a modern LCD. "The fast beam of a CRT scope and it's variable brightness and it's phosphor's persistence of vision is what makes this magic possible. I'm using an old Tektronix 2445A. Not all scopes have a Z-axis input (or XY mode), so check your specific scope model."

The board is now available to buy from the FiveFish Audio Tindie store, priced at $12.