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Messy MDC DCC install (Circuit Advice Please)

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Messy MDC DCC install (Circuit Advice Please)
Posted by SpaceMouse on Friday, October 9, 2020 7:17 PM

The 2-6-0 came with a 9-pin harness, and I have bunch of Digitrax decoders that plug right in. The problem the harness is too short for the decoder to fold back on itself, so even though there's enough room for the decoder, I can't get it to the empty spot. 

When I tried, I broke loose a power pick-up from the rear truck. Look at the rear truck. It's melted to ____.

That led you guys to suggest I get rid of my pencil and get a soldering station. I now have replacement trucks. 

Here's a photo.

Now when I flip the board over, I find an eight-pin harness. I have an NCE N-scale decoder that would plug right in to that sucker. 

I figure that the board is like the light board in Diesels. 

The problem is that the rear light connects to that board and the board gets power from both sides of both tender trucks.

And someone got a great idea to wire the harness Goth style--all black.

I'm open to suggestions.

Chip

Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.

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Posted by SpaceMouse on Saturday, October 10, 2020 3:05 AM

It seems I've had this conversation before:

http://cs.trains.com/mrr/f/744/p/268319/3046174.aspx#3046174

The consensus is to rip out the board and hard-wire an 8 pin harness.

Not a problem. Sort of. The wires coming from the engine are still all black. I guess I have to trace the wires from the engine.

Randy

2 right rail pickups tie together, go to the red decoder wire.

2 left rail pickups tie together, go to the black decoder wire.

blue wire from the headlight plus blue wire to the backup light tie together and go to the blue wire on the decoder.

white to the loco for headlight, yellow to the other wire of the backup light.

Either tie the pickup wires together then tap off, or just make a 3 way splice with the approriate decoder wire.

Or use a strip of copper PCB - saw cuts to make a series of parallel bu unconnected pads, solder all right side wires to one pad, left wires to another, etc. That way you cna shorten the truck pickup wires in the tender (just glue the little PCB on the tender, and the only wires that need to be slightly longish would be the ones to the decoder itself, to give you enough slack to lift it up and pull the 9 pin to remove it.

                                  --Randy

Chip

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Posted by trwroute on Saturday, October 10, 2020 7:48 AM

That's what I've done before...just remove the board and hardwire a decoder.  It's easy to trace the wires if you have an ohm meter.

Chuck - Modeling in N, HO scales and anything narrow gauge

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Posted by SpaceMouse on Saturday, October 10, 2020 9:53 AM

Chuck
It's easy to trace the wires if you have an ohm meter.

That's the thing with the LED readout and the nob that you turn clear to the right and use to test your solder connection when it beeps.

Chuck
...just remove the board and hardwire a decoder.

Right now I want to make one of the ten or so decoders I have work, then when I can afford a sound decoder, I want to be able to plug it in. The loco already has an 8 pin harness that connects the board.

Okay, here's my plan:

I have an 8 pin to 9 pin adapter for one of my Digitrax decoders. I could plug that it to the existing 8 pin and use the color on the adapter to identify the wires wires on the existing harness. I could then modify the wires I need to--power and lights--and use the existing adapter to use the Digitrax decoder.

That leaves two problems:

I'm assuming the people who wired it did it correctly. I've heard of at least one story of a professional installer plugging in a decoder only to have it short the locomotive. The person who wired it used the frame to conduct DC power. This is the that same make, model, and road number. 

And I have no idea what size resistor to use. After my last post about LEDs, I don't know if DCC is:

1) a 28v square wave

2) 14v AC

3) a 7v ionic storm burst

Chip

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Posted by Mark R. on Saturday, October 10, 2020 10:01 AM

The function output to your LED is 1.4VDC less than your track voltage using PWM.

Mark. 

¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ

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Posted by SpaceMouse on Saturday, October 10, 2020 10:16 AM

Mark

The function output to your LED is 1.4VDC less than your track voltage using PWM.

Mark. 

So if R=I/V and V=x-1.4V...

the answer to Life, the Universe and Everything is still 42, right? 

HmmConfusedConfused

Chip

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Posted by Overmod on Saturday, October 10, 2020 10:27 AM

SpaceMouse
And I have no idea what size resistor to use. After my last post about LEDs, I don't know if DCC is: 1) a 28v square wave;  2) 14v AC;  3) a 7v ionic storm burst

Buzzer!!!

Correct current answer is 'none of the above'; to your decoder it looks like fast pulsed 14V DC (no matter which way the locomotive faces on the track).  Just add 17 to 20% to whatever resistor value you were using for 12VDC if you want to play safe.

As you trace the wires put a corresponding dot of paint or color on the black insulation near each end.  That may help the 'next time' you need to troubleshoot or adapt something.

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Posted by Overmod on Saturday, October 10, 2020 10:38 AM

SpaceMouse
So if R=I/V and V=x-1.4V...

It's so simple... So very simple... That only a child can do it!

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Posted by SpaceMouse on Saturday, October 10, 2020 12:51 PM

Overmod
Just add 17 to 20% to whatever resistor value you were using for 12VDC if you want to play safe.

I'm 99 to 101% sure you are specifying a 1200 ohm resistor. However, I have no idea those are 3v LEDs in the loco. I can find the part number, but not the specs.

I know I have 1000s and 240s and several others, but I'll have to get a color chart out to see what they are. I don't want to daisy chain them. I may have to order some.

Chuck
It's easy to trace the wires if you have an ohm meter.

I'd love to know how to ID the wires with an ohm meter.

Chip

Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.

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Posted by SpaceMouse on Saturday, October 10, 2020 12:56 PM

Rich--I want to thank you again for the replacement parts you sent. They will come in handy. It took me a while to put 2 and 2 together as to who you were.

If I'm right, I can use the insulated wheels from the damaged truck on my 2-6-2T project to get power from the pilot and trailing trucks.

Chip

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Posted by rrinker on Saturday, October 10, 2020 1:11 PM

 It looks to me like there is plenty of wire attached to that 9 pin to fold it up - maybe bunch the wire up in front of the decoder instaead of trying to flip the decoder upside down. Or use a smaller 9 pin decoder.

 I wouldn't put any sort of 8 pin plug in if you hard wire the decoder, the decoder already has a 9 pin plug with wires, so you can remove the decoder if necessary. No need to add yet another plug and socket.

 Or, here's an idea - desolder the wires going to the 9 pin plug, and solder the wires from the decoder into those same holes. Easy peasy and you can leave the wires as long as you need.

 The answer for LEDs on DCC is almost always 1K. If they are too bright (but you won't blow one out), use a 2.2K. You have a 50/50 chance of getting the polarity right, the LED won't blow if backwards, just won't light up - as long as you didn't forget the resistor. If it worked before, and now doesn't, you probably just have it wired backwards.

                                  --Randy

 


Modeling the Reading Railroad in the 1950's

 

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Posted by Lastspikemike on Saturday, October 10, 2020 2:28 PM

Overmod

 

 
SpaceMouse
And I have no idea what size resistor to use. After my last post about LEDs, I don't know if DCC is: 1) a 28v square wave;  2) 14v AC;  3) a 7v ionic storm burst

 

Buzzer!!!

 

Correct current answer is 'none of the above'; to your decoder it looks like fast pulsed 14V DC (no matter which way the locomotive faces on the track).  Just add 17 to 20% to whatever resistor value you were using for 12VDC if you want to play safe.

As you trace the wires put a corresponding dot of paint or color on the black insulation near each end.  That may help the 'next time' you need to troubleshoot or adapt something.

 

Is that fast as in 9,000 Hz fast? Or am I lost in the DCC world again?

Alyth Yard

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Posted by SeeYou190 on Saturday, October 10, 2020 8:53 PM

SpaceMouse
the answer to Life, the Universe and Everything is still 42, right? 

Yes, 42 is the answer to everything.

That is about the best answer you will ever get from me in a DCC thread.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by SpaceMouse on Saturday, October 10, 2020 9:17 PM

rrinker
I wouldn't put any sort of 8 pin plug in if you hard wire the decoder, the decoder already has a 9 pin plug with wires, so you can remove the decoder if necessary. No need to add yet another plug and socket.

I know the sound decoders I will eventually--hopefully soon--be putting in  will use an eight-pin harness. It doesn't make sense to me to hardwire a decoder or the 9-pin harness then have to do it all again. I'm not that proficient yet.  

Chip

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Posted by rrinker on Saturday, October 10, 2020 9:44 PM

 TIme has passed that by, the common format now is all turning to the 21 pin format, so you might want to repalce the stock board with a 21 pin motherboard - Nix Trainz has the DecoderBuddy Mini which is a small one that will fit. Comes with the resistors (though they are not built in to the board like the larger ones). All you need to do is figure out which wires from the loco are which and solder them to the pads on the motherboard. Plug in a 21 pin motor decoder - good to go. Swap out later with a 21 pin sound decoder.

https://nixtrainz.com/description

                                  --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 SpaceMouse on Saturday, October 10, 2020 10:11 PM

Randy
 TIme has passed that by, the common format now is all turning to the 21 pin format, so you might want to repalce the stock board with a 21 pin motherboard - Nix Trainz has the DecoderBuddy Mini which is a small one that will fit. Comes with the resistors (though they are not built in to the board like the larger ones). All you need to do is figure out which wires from the loco are which and solder them to the pads on the motherboard. Plug in a 21 pin motor decoder - good to go. Swap out later with a 21 pin sound decoder.

When I was in college, I kept up with the PC world. Then somewhere around Windows 7, I started to care less and less with keeping up. 

Right now, I'm not hearing as well as I used to, so even the cheap decoders sound good to me. The cheap ones I've been looking at are 8-pin.

And I have a lot of 15 year-old decoders. I'll put them in until I get sound.

But this will be case by case. Who knows what I'll do with the Climax A. The other two 2-6-0s are wired with 9-pin. I have a couple that are hard-wired. 

Chip

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Posted by rrinker on Sunday, October 11, 2020 10:32 AM

 Which ones? Even if you don't care about the sound quality, you don't want to give up on the drive quality. Might as well not bother with sound, really. But keep in mind a lot of 8 pin decoders are actually 9 pin decoders with a harness included that goes from 9 to 8 - which can be unplugged at the decoder end so the decoder plugs directly into a 9 pin. 

                                               --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 SpaceMouse on Sunday, October 11, 2020 11:06 AM

Subject change: I have a bunch of bread boards with 18 x 24 holes. I was thinking that using one with 4 x 10 holes might neaten things up. Is it worth doing? I'm more inclined to do a 9-pin if I thought it was just a matter of doing a couple desolder resolders.

Chip

Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.

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Posted by richg1998 on Sunday, October 11, 2020 11:37 AM

Some years ago I jusst unsoldered the 9 pin and the tender light plug. Soldered in a SoundTraxx Micro plus 1k resistors for the LED's. Did it with the 2-8-0. Strange they both use the same boiler. Same with the 4-4-0. That came with an MRC sound on board. Lousy. Removed it.The gearing is nice and they run well, though.

Plaine Jane's next to Bachmann steamers. No real detail. Athearn no loger makes them I believe.

Rich

If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.

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Posted by SpaceMouse on Monday, October 12, 2020 10:17 AM

Okay, it's not a breadboard. My bad.

It's a generic circuit board with holes on one side and a circle of copper for soldering on the other. If you know the term for it, I'd appreciate it. It calls itself PY-5CM*7CM. Coincidently, it seems to measure 5 x 7 cm.

Here's my plan.

   

I plan to mount this in the front part of the tender, insulated from the frame. 

I've never done this before so I could use some clues. Since I don't know what it's called Professor Google couldn't help me.

I numbered my questions.

(1) What do you call that board?

(2) What's the best way to cut this down to size?

(3) I'm assuming I solder jumper wires on the bottom to connect things, right?

(4) The dead spot on my frogs measure 1 3/8" long. The tender wheel separation is much longer. I don't think I need a Keep Alive, do I?

(5) To solder, I plan to use a needle tip and 0.8 mm No Clean Flux core solder. What would be a reasonable temperature setting? 

(6) Advice?

Chip

Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.

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Posted by Overmod on Monday, October 12, 2020 11:18 AM

(1) I would call this 'perfboard'.  To me 'breadboard' implies more specific layout and labeling, not necessary for your intended use.

(2) One way is 'score and snap' -- if the perfboard isn't cheap and you find the pads popping off as you snap Surprise.  A thin cutoff wheel or thin-kerf razor saw also work with care.  Clean up edges with a file or fine sandpaper afterward.  Others will have suggestions from their experience.

(3) You can solder to the pads, but often using projecting component leads or even one or two turns of wire-wrap on those leads is useful too.

(4) "suck it and see"!

(5) Temp will be determined by your solder's alloy.  I recommend the lowest temperature that gives clean shiny joints.  I still advise you have external no-clean flux in addition to the solder core; others will have a different opinion...

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Posted by richg1998 on Monday, October 12, 2020 11:57 AM

I have done the same. Over the years. All good advice. Use plenty of light and an Optivisor if eyesight issues like me. Inspect carefully.

I did many electronic projects the past twenty five years with perf boards.

Check the loco and tender on a program track FIRST. That saved me once.

Good luck.

Rich

If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.

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Posted by richg1998 on Wednesday, October 14, 2020 9:02 PM

Some years ago I used Vero board with an App to design electronic layouts. The App was not necessary but helped.

Vero board has strips of copper you can cut with a sharp knife. Really convenient. Amazon sells it now.

I bought it kind of cheap at the time from ebay from the UK.

Rich

 

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Posted by SpaceMouse on Friday, October 16, 2020 5:43 AM

I was thinking about the rear LED. It's the little yellow 1mm square on the end of the lead going off to the right.

  

That lead plugs in to the rear lamp frame as is. 

Now notice the cylindrical shape leading to it. I think it's possible that there is the correct resistor in there for the small LED. The whole assembly plugs into a 2-pin harness on the light board.

Is there any way to tell what's going on there without messing it up. Have multimeter. Will try to use it.

Rethink--okay maybe over-think. 

The LED plugs into the white 2-pin harness in the left center of the board. Click photo to enlarge.

One lead goes to the blue wire of the nine pin harness. The other goes to the round black gizmo with 100 printed on it, lower and just right of the harness (marked L1). From there it goes to the yellow wire on the 9-pin harness. (I think.)

There's another round black gizmo that is just to the left of the other one (marked L2). The top is cracked open a little and you can see part of a coil of thin wire like you would see wrapped around the armature of a motor. 

The resistor (R1) two gizmos to the right of L1 measures .972K. 

I'm assuming that I can ignore all my ramblings and just use the 1K resitor I had originally planned. 

Anyone want to try to explain what's going on in that circuit?

 

Chip

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Posted by rrinker on Friday, October 16, 2020 8:43 AM

 The square black things with coils in them are inductors - they are probably in series with the wires to the motor, orange and grey. The little blocks that are yellow are capacitors, the ones to the left of the wires going to the 9 pin connector are probably between the motor wires and ground. All that stuff is for RF suppression and can be bypassed - the capacitors can be just cut off, but the inductors need to be replaced with jumper wires. These same things are on Bachmann locos. They interfere with better quality decoders using BEMF motor control.

The small black squares are resistors, the 100 marking means 1K. One if the front headlight, the other is for the reverse lights - so it is not likely there is a resistor under the shrink wrap at the LED.

The big black squares are diodes. Those are used in the motor circuit for continuous lighting - basically restricting the voltage to the motor so the LEDs can come on when using DCC before the loco actually moves. Those are likely bypassed if the decoder is plugged in to the 9 pin connector. 

In short - the only thing on there needed if a decoder is installed are the 1K resistors. If you supply your own, everything including that entire board can be removed.

                                        --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 SpaceMouse on Friday, October 16, 2020 11:29 AM

Randy
In short - the only thing on there needed if a decoder is installed are the 1K resistors. If you supply your own, everything including that entire board can be removed.

I think I'll steal that 2-pin harness. I don't think the light leads will reach the far end of my board where they need to connect. 

Chip

Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.

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