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8 pin or 9 pin decoder, what's the difference?

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  • Member since
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8 pin or 9 pin decoder, what's the difference?
Posted by Joe HO Fan on Thursday, September 26, 2013 11:33 AM

This forum has been an invaluable source of information and help.  I'm still a bit of a noob, so bear with me.  I bought all my decoders way back in 2002, then all sat unused until last summer, when I finally retired and had time to work on my layout and stuff.  All those old TCS decoders still do what I need.  It has come time to purchase some more decoders.  I notice that some locos "dcc ready" advertise that they are for 8 pin decoders, all my other decoders are 9 pin.

What's the difference other than the obvious number of pins.  Note that for the most part, I only run basic locos, lights and forward and reverse.  Will a 9 pin decoder work with a loco advertised as "dcc ready for 8 pin"?

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Posted by Mark R. on Thursday, September 26, 2013 12:19 PM

The only real difference between the two is that the nine pin has functions 5 (green) and 6 (purple) within the plug, where-as the eight pin plug only has function 5 on the plug and function 6 is a free hanging wire.

The next step will be the 21 pin plug which has been a European standard for some time. The new factory equipped engines with Loksound decoders now have this 21 pin technology.

Think 8-track to cassette to CD technology ....

In order to use your 9 pin decoder in an engine only equipped with an 8 pin plug, you have two options. Cut the plug off your decoder and hard wire it to the board, or get some adaptor harnesses from TCS that convert the 9 pin plug on your decoder (sounds like you have T1's) to an 8 pin with a free wire.

Mark.

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Posted by jeffrey-wimberly on Thursday, September 26, 2013 12:41 PM

You could use something like THIS or it's shorter version THIS. They're made for Digitrax decoders but I've seen some friends use them with TCS decoders without a problem.

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Posted by gregc on Thursday, September 26, 2013 6:09 PM

greg - Philadelphia & Reading / Reading

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Posted by rrinker on Thursday, September 26, 2013 10:29 PM

 Both are standards, so you can use harnesses from any manufacturer to adapt one to the other. TCS has lots of different harnesses wwith different wire lengths and different orientations of the wires to the 8 pin end, but a Digitrax 9 pin to 8 pin harness will work fine in a TCS decoder.

 

 Now, about those TCS decoders - those 2002 vintage ones don't have BEMF. They're good decoders, but the newer ones are much better.That's the downside of stockpiling too much in a rapidly changing high tech field. I use the newer ones in everything - always work great, and the lights work great with LEDs.

                    --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by Joe HO Fan on Thursday, September 26, 2013 10:52 PM

Ok, good info.  I actually have a couple of those adapters.  When I bought the original TCS decoders, I also bought a couple Lenz decoders and one of them came with the adapter.  So, I should be good.  Thanks for helping me out.

Joe

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Posted by wjstix on Friday, September 27, 2013 8:53 AM

Except for the rectangular decoders that have an eight-pin plug permanently attached underneath them, or light-board-replacement "drop-in" decoders, I think all the other decoders are nine-pin-connection decoders. It might not look that way at first glance however. Many come with a harness attached that ends in just wires (for a "hard wire" installation) or with an eight-pin plug. Sometimes the area where the nine-pin plug is, is covered by the plastic covering the decoder, so it isn't immediately visible. For example, with the old Soundtraxx "LC" sound decoders, they came with just wires sticking out. But if you took a hobby knife or razor blade, you could remove about 1/8" or so of the plastic "tape" like covering where the wires came out, and remove the nine-pin harness and plug in a nine-pin to eight-pin harness in it's place.

Stix
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Posted by rrinker on Friday, September 27, 2013 9:37 AM

 Some just have wires soldered right to the board, they are becoming rarer, at least in the larger size decoders, but for smaller ones, that 9 pin socket takes up a significant amount of space so it gets left off - you wouldn't have anything like the tiny Z scale decoders that are smaller than the head on a dime if they had a physical connector on them.

                    --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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