The Retro Channel's Video Debug Board Provides Easy Scope Probing for Vintage Hardware

If you've ever juggled oscilloscope probes and a video cable while diagnosing faulty hardware, this is the board for you.

Gareth Halfacree
27 days agoRetro Tech / Debugging / HW101

Mononymous vintage computing enthusiast Mark, of The Retro Channel on YouTube, has designed a board that aims to make it easier to diagnose video problems in vintage hardware — or to reverse engineer unexpected signals.

"The main purpose of this board is to simulate the 75 ohm termination for analog video signals. This allows for analyzing video signals from most common analog video connectors with an oscilloscope," Mark explains of the Video Debug/SCART Breakout Board. "From there it can be determined what signals are present and if the signals conform to standard specifications."

The board includes video and audio inputs, including a chunky SCART connector — also known as Péritel or EIA Multiport — for devices that use it. Each signal is brought out to loops to which oscilloscope probes can be connected, allowing for any combination of signals to be observed. "Anyone who has tried probing video signals while they are connected to a display will know how difficult it can be," Mark explains of the board's usability, "especially if the cable itself contains passive components. And probing analog video signals at the source without termination is a pointless exercise."

The breakout board allows for composite, RGB, and YPbPR signals to be tested from RCA, SCART, and S-Video inputs, along with luma, chroma, sync, and the SCART blanking and function-switching pins. The audio connections, meanwhile, are scopeable but lack the jumper-selectable termination resistors — "as it makes little difference for line level audio and isn't the main focus of this design," Mark explains.

"As most of the video and audio signals are shared between the connectors, only one input should be used at a time," Mark notes. "However this does allow the board to function as a SCART to RCA (or S-Video) adapter by removing the 75 ohm termination jumpers. Keep in mind this isn't the main purpose of this board and is not intended to substitute a purpose-built SCART to RCA adapter, but it may get you out of a tricky situation where you only have a SCART cable and your display has RCA or BNC connectors."

Mark is selling fully-assembled versions of the board on The Retro Channel's Tindie store at $35.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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