8-pin vs 9-pin decoder harnesses

Aug 31, 2010 4 Replies

A question from someone who is not decoder-savvy:



Why do some HO locomotives come with 8-pin DCC harnesses (for example, the Atlas SD35) versus some that come with a 9-pin harness (for example, the Walthers RS-2)? What's the difference in operation of the plug? How does that limit decoder choices?



Atlas SD35:

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"... NMRA 8-pin plug for DCC ..."



Walthers RS-2:

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"... factory-installed 9-pin DCC harness=85"


Mark Mathu schrieb am 31.08.2010 19:54:

The 8-pin is more common in Europe while the 9-pin is widely used in the US. In fact I would have serious problems to get a 9-pin decoder over here in Germany (except an US decoder imported by a special US model railroad store). The 8-pin plug has often only 7 line connected. PA1 and PA2 (green and brown) are often not or only green (PA1) is connected. The 9-pin plus is fine to have all lines and usually has all lines connected.

Can a person use an 8-pin decoder in a 9-pin socket? What are the results?

Mark Mathu wrote in news: snipped-for-privacy@4ax.com:

The form factors are different, the 8-pin is 2 rows of 4 pins, while the

9-pin is 1 row of 9 (much smaller) pins. The difference is merely physical, adapters are available to go from one to the other.

Pictures are available here:

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Puckdropper

Yes, with a 8 to 9 pin adapter harness. In fact I buy 'blank' eight pin male plugs and solder up my own harness. I use a lot of Train Control System T1 decoders which are 9 pin but they came with the female plug on a hardwire harness to be soldered into the model. But I take the eight pin blanks, color match the harness to the plug and solder it up. Voila

- 9 pin decoder on an eight pin harness. And of course you can buy those harnesses premade from TCS and others.

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