17 July 2010

Anatomy of a presumed parallel cable

The cable pictured blow (the bottom one) was being sold in eBay (UK) as "Parallel Printer 25M/25M Cable 3M - Switchbox DB25" by a professional dealer. I got one of these to drive some project, no joy, nothing worked at all. I even fried a NetMos paralell port pci card in the attempts.

Signals didn't happen where expected, spurious voltages and interference were all over the place, and the said cable looked suspiciously thin (5 mm diameter, bottom) when compared to some real, well worn and proven parallel port cable (7.5 mm, top). Time to rip up its plastic belly. O surprise, o wonders, what do we have here?

Inside only 11 teeny wires are to be found. These connect pins 2, 3, 4, 5, 6, 10, 11, 12, 13, 15 and 25. Nothing to do with IEEE 1284, and no way this would ever work.

BTW one may wonder which drugs the guys who "set the standard" for this mess were high on.

As for the incriminated cable, I am asking the seller for a refund.
I got from the usual sources a nice stock of used, well worn and well tested paralell cables. They are centronics ended though, so they will require some handling...

UPDATE: The seller was very quick and responsive, and issued a full refund. He started testing his (unlabeled) cable stock...

In the mean time, I retraced that particular cable pinout to a "Laplink cable". Seems everybody has forgot about those, hadn't seen one in more than 15 years!

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