Making your own analog video cables - Page 1
Forum section: electronics / general

author: Unknown
author_rank: Unknown
timestamp: January 12, 2015, 07:00:35 am
content: I'm making up some video cables for a number of my vintage computers that either didn't come with any or have crappy el-cheapo composite leads.The question I have is when we're talking about analog video (either composite or component/s-video output), is there a particular type of cable I should be using? Does impedance matter?

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 12, 2015, 07:05:44 am
content: If your (unidentified) vintage computers have composite video output, then the quality of the video, at its best, probably won't be materially affected by the type of cable unless you use really terrible cable or you are running long distances (many meters, etc.) I make my own BNC and audio (RCA, XLR, TRS) cables, but DIY S-Video (Y/C) and component just seem more trouble than any benefit you might derive from the exercise. Especially when you can probably find those kinds of cables free by a bit of dumpster-diving, etc.

author: Unknown
author_rank: Unknown
timestamp: January 12, 2015, 07:08:46 am
content: At the moment I'm focusing on my Commodore 64 but I have others. It uses an 8-pin U-shaped DIN connector (not the more common DIN 45326). It has separate pins for Y/C so I was planning to patch those through to a CRT broadcast monitor that I have (with BNC connectors). There is also a mono audio pin. So essentially what I need is an 8-pin DIN which breaks out to 2x BNC (or 3x if I want to include a composite video out) and 1x BNC/RCA for audio.I find BNC easiest to work with as most of my monitors (CRT and LCD's) have BNC inputs but I also have a stack of adapters which I can use if need be.

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 12, 2015, 02:59:13 pm
content: Still not sure what is your "8-pin U-shaped DIN connector"?But if it is like most DIN connectors, it is too small to take several RG-59 size conventional 75-ohm cables.So you would probably find it much more convenient to use a "miniature" 75-ohm coax like RG-179/UActually for such a non-critical application and short distance, the impedance of the cable is not all that important.One of the miniature 50-ohm coax cables (which are probably easier to find) would work just as well.

author: Unknown
author_rank: Unknown
timestamp: January 12, 2015, 06:06:47 pm
content: Quote from: Richard Crowley on January 12, 2015, 02:59:13 pmThanks for that.The connector I'm talking about is a standard DIN sized plug but has the same kind of pin arrangement as the DIN 41524. Lumberg make the exact plug I'm after (http://au.element14.com/lumberg/sv80/plug-din-straight-8way/dp/1321482?ost=1321482). They also make the more common SV-81 (DIN 45326) which is still an 8-pin plug but pins 7 and 8 are curved around the plug in more of a circular layout (this is what you normally find on your older audio gear) whereas on the SV-80 the pins represent more of a 'U' shape. It's a subtle difference but one will fit where as the other doesn't (without being forced into the socket). I've included an image of both below.That connector will also accept cable diameters of 4-6mm. There is a larger one which will take 6-8mm cable.

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 12, 2015, 07:43:54 pm
content: I would make a "break-out" box to go on the back of the monitor with one of those female DIN connectors, and broken out to RGBHV (or whatever) short coax cables to connect to the BNC connectors on the back of the monitor. Making a multi-coaxial cable for such a small connector is a thankless job.

author: Unknown
author_rank: Unknown
timestamp: January 12, 2015, 07:46:34 pm
content: Yeah I agree, a breakout box seems the way to go. I guess I could buy a pre-made cable with the DIN plug I want, cut the other end off and solder it to BNC plugs on a breakout box. That way I just have to use standard BNC leads from the device to the monitor.

author: macboy
author_rank: Super Contributor
timestamp: January 12, 2015, 08:18:07 pm
content: Quote from: Richard Crowley on January 12, 2015, 02:59:13 pm75 ohm mini coax is cheap and easy to find. Just hack apart an old VGA cable. If the VGA cable is of any decent quality, the coax in there should be good for well over 100 MHz over several meters.

author: Richard Crowley
author_rank: Super Contributor
timestamp: January 12, 2015, 08:21:31 pm
content: Quote from: macboy on January 12, 2015, 08:18:07 pmSure, no problem FINDING it. But terminating 3 or 4 or 5 miniature coax cables into a DIN plug (even the "full-size" variety) is a very tricky thing to get right because everything (including the pin terminals and all the clearances) is so very small.