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8-Pin DCC in Proto 2000 E7 - Which One is Number 1?

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    January 2020
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8-Pin DCC in Proto 2000 E7 - Which One is Number 1?
Posted by MooMooHolyCow on Wednesday, January 29, 2020 7:34 PM

Hello. I have maybe a mid-1990s Proto 2000 that's DCC ready with an 8-pin, 2-row socket. And.. like a dummy, I pulled out the plug without looking at the orientation. Can someone tell me which pin is #1 so that I can put my encoder in the correct way? 

My plug is at the very aft-end of the engine (just in case there are different versions). Right by the socket, the board reads 294-X008 E7. There is a deceptive "J1" on the board by the row cloest to the front, poart side, second column, but this can't be Pin #1. 

Thanks, in advance.

 

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Posted by RR_Mel on Thursday, January 30, 2020 9:46 AM

Place your locomotive on a piece of track so that the engineer side is forward (right rail).  Pin 8 on the NMRA connector is pin 8 (Red) Right Rail.
 
Measure between the right rail and the connector and pin 8 will measure close to 0 ohms.
 
 
 
 
 
 
Mel
 
 
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
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Posted by rrinker on Thursday, January 30, 2020 10:07 AM

 Good news is, if you plug it in backwards, it won't fry anything. It will run backwards, and the lights won't work.

                               --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 mbinsewi on Thursday, January 30, 2020 10:38 AM

rrinker
 Good news is, if you plug it in backwards, it won't fry anything. It will run backwards, and the lights won't work.

Yep, I learned that.  Smile, Wink & Grin

Mike.

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Posted by wjstix on Thursday, January 30, 2020 11:51 AM

Ya, based on my experience, no matter how hard you study the issue, the decoder will go in the wrong-way around about 75% of the time. Not worth losing sleep over, just plug it in and try it. As Randy says, if it goes backwards when it should go forward and the lights don't work, remove it and rotate it 180 degrees.

Stix
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Posted by gmpullman on Thursday, January 30, 2020 12:13 PM

Hello,

MooMooHolyCow
Right by the socket, the board reads 294-X008 E7.

If you study the socket very closely you will see that one of the solder pads (top row, right) on the board is square, the other 7 are round. Normally this would designate "Pin 1". Sometimes there is a little triangle pointing to it with screen-printing but this is not the case here.

 

 L-L_E7-8 board1 by Edmund, on Flickr

 

     You can easily follow the trace from Pin 5 to the motor minus

(M —) wiring pad.

 L-L_E7-8 board-W by Edmund, on Flickr

 Oddly, there is no mention of the socket in the stack of L-L or Walthers documentation that I have collected on my fleet of E-units.

Also, you can easily follow the traces from Pin 4 and 8 to the rail-pickup pads on the board (Life-Like has them marked + and for some reason).

Hope that helps, Ed

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Posted by RR_Mel on Thursday, January 30, 2020 12:49 PM

Constantly learning on the Forum, Thanks Ed.
 
My Proto SD-9 has a 1 next to pin 1.  When I first started into DCC I put a red dob of paint next to pin 8 on all of my 8 pin NMRA connectors for quick ID.
 
 
 
 
 
 
 
Mel
 
 
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
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Posted by Overmod on Thursday, January 30, 2020 12:54 PM

Use of something like "J1" is a common convention on circuit boards for either 'jacks' or 'jumpers' -- in either case where something external to the board is going to be plugged in.  Usually the numbers refer to specific jack/jumper-socket locations, not to wire arrangements or numbers of wires in the connectors themselves.  On the other hand, I'm familiar with connectors having at least some of the pins/sockets overmolded having identification of numbering  by at least a couple of digits (cf. the typical 40-pin IDE/PATA hard-drive connector) where there is potential ambiguity...  

Lest you think this connector layout is a weird anomaly, see this discussion of the matter from stackexchange.com which, in the comments, explains why the numbering in the socket part of the connection runs as it does.

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Posted by Canalligators on Saturday, February 1, 2020 8:37 PM

So why didn't the designers use keyed connectors?  Pet peeve...  I once raised a stink with the board designers at work about not keying the connectors on prototypes.  I shouldn't have to get out the schematics to check connector orientation.  It costs $0 extra.

End rant.  Sorry.

Genesee Terminal, freelanced HO in Upstate NY
  ...hosting Loon Bay Transit Authority, run through Amtrak and CSX Intermodal

CP/D&H, N scale, somewhere on the Canadian Shield

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Posted by rrinker on Saturday, February 1, 2020 9:02 PM

 Because they didn;t have to - backwards doesn't break anything. They are just off the shelf connectors, the NMRA didn't design them or anything. You plug it in, see if it works, if not, slip it around. Nothing is damaged.

                                                --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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