Take a Big-Breath, and get ready to Dive-Deep...

Dear ???

First-off, interesting challenge as a "first go" DCC conversion!
I have to ask, what is it about the existing ex-factory SoundTraxx decoder which is prompting this rather-large "voyage of discovery"? Most modellers find the ST decoders to be more-than capable, reliable, and sonically-acceptable as-is?

Anywho, you asked some deep questions, so let's dive in...

Per the NMRA DCC Wiring Spec:

Orange = Motor +ve
Grey = Motor -ve
Black = Left Rail
Red = Right Rail

(Now, here's the bit that matters to your 6-wire loom)

Blue = Function Common (+ve volts)
White = Front Headlight (F0f)
Yellow = Rear Headlight (F0r)
Green = "Output 3"
Violet = "Output 4"
Brown = "Output 5"

NOTE! The decoder acts as a massive "Input> Output matrix",

IE Fn Command IN --> Decoder "matrix" --> Physical (specific wire color) "OUTput n"

which means that while we can predict that a "logical output" does to a given Physical "Wire color",
(EG "the Green wire flashes like a rotary beacon")

what we do NOT know, without further investigation,
which "F-key" (Function Input Command) controls what "Wire Color" output...
(IE when you press the "F?" button on your DCC throttle,
which of the colored-wires reacts/changes/does something?)

That said, to address some of your questions in-order of appearance:

Let's nail down some "knowns":

Firstly, keep the following in mind: Whenever a Light can independently do something, it must have it's own specific discrete physical output wire. This Is Important to keep in mind, so you don't get tangled further down the line...

Moving on...

- In the DCC world, "F0" (Function Zero) is the "Headlight control".
It is commonly logically-broken down into "F0f" (Function Zero Front)
and "F0r" (Function Zero Rear)

Hopefully it is clear from this that Logically , One "F-key" (F0) is controlling TWO Physical Function Output wires,
with each wire being programmed so it only operates when the loco is in the appropriate "Direction".

As above, per NMRA Wiring spec, we KNOW that

White = Front Headlight (F0f)
Yellow = Rear Headlight (F0r)

(See, TWO wires, one for each of the "Headlights",
despite both being turned On/Off by the ONE common "F0" function key)

NOTE! I'm not mentioning the "Blue Common (+ve volts) because, well, it's common and connected as the "return path" for all "Function outputs".... it's kinda "just assumed to always be there, and along for the ride"...

So, go back, take your time, read it again til it makes sense,
then we can continue... (We'll wait...   ).

Now, onto the next bits...

- We do NOT know (you have not stated) which "F-keys" on your DCC throttle control the "Ditch Lights" or "Number boards", so there will necessarily be some holes in the next comments which you are the-best-placed to answer. However, what we DO know is:

- The "Ditch Light" behaviour is another "Single Logical F-number key INPUT controls Multiple physical wire color Outputs" (particularly if the Ditch lights FLASH alternately in response to a Horn blast or similar)

- The "Cab Light" feels like a "Single Logical F-number key INPUT controls a SINGLE physical wire Output"

Therefore, with "White" and "Yellow" wires taken (Front and Rear Headlight respectively),

and THREE (3) LEDs/Bulbs to control with the THREE (3) remaining "Function output" wires
(2x "ditch lights" + 1x "cab light")

It's pretty safe to assume that the "Green", "Violet", and "Brown" wires feed the Ditch (x2) and Cab lights.
I'm assuming that it's:
- Green = Ditch Left
- Violet = Ditch Right
- Brown = Cab light

but that is an educated assumption, which really should be tested in-situ with a multimeter or similar...

but to gather them all together in table form:

Function Key           Human-name     Wire-color/Output    Task/Location-on-loco
F0 (+ DIR = Fwd)    Headlight           White                        Front Headlight
F0 (+ DIR = Bkwd)  Headlight           Yellow                       Rear Headlight
Fx                            DitchLight          Green                        Left Ditchlight
Fy                            DitchLight          Violet                         Right Ditchlight
Fz                            Cab light            Brown                       Cab light

NOTE! "F(letter)" Function keys are unknown/unconfirmed at this time
NOTE! I may have the Ditch and Cab Light <> color-wire assignment completely wrong,
and I do not own one of these locos myself to confirm here.
CHECK THOROUGHLY BEFORE PROCEEDING!!!

2 things strike me:
- You'll note that the Violet Function Output wire is conspicuous by it's absence on this pic
(Where did Violet go?)

- The brown wires seem to have a connector on the end, where does that Connector go to?
(Hazarding a guess, it may be connecting to the Cab light? If YES, then the choice of "2x brown wires" may be an attempt to make them less visually-intrusive thru the cab windows?
Alternatively, they may be SPEAKER wires, in which case, you MUST go-back and do some serious investigation of exactly where the Green, Violet, and Brown Function wires actually come-from/go-to!!!)

Note that there are some labels on the Decoder Buddy Aux board, which gets us started:
- "U+" = Function Common (+ve volts)

...now, where have I seen that before???
Oh yes, That's the BLUE wire...

- I see "0f" at Bottom Left and "0r" at Bottom Right of the pic...
...I'd guess they match the "F0f" (White) and "F0r" (Yellow) Headlight lines...
(...but c'mon, honestly, you were already waaaaaaaay ahead of me here, weren't you....   ).

Now, this is where it gets tricky, and We as the Modeller have to make some decisions.

- As above, there is no Official Specification or "Hard and Fast Rule"
RE "which F-number turns Ditch Lights and Cab Lights On/Off"

- The decoder Does Not Care, and can be configured to map (almost) ANY "F-key" INPUT to control any of the available "Wire color" Physical Outputs
(IE it could be "F1", or "F28" which turns the Cab light On/Off, or any "F-key" in between...
...the DCC system just issues the "Fn command",
and the Decoder works out which-if-any Physical-wire Output should respond...)

- That said, if we assume that the NixTrainz terminology of "An" terminals lines right-up in sequence behind the "F0f"/"F0r" Headlights, then _I_ would go with the following Physical Wiring config:

Task                         Wire Color      DB Aux board terminal
Front Headlight        White              0f
Rear Headlight         Yellow             0r
Left Ditch                  Green             A1
Right Ditch                Violet             A2
Cab light                   Brown            A3

...and then program the new 21-pin decoder so "Output 3"/"A1" (Left Ditch), "Output 4"/"A2" (Right Ditch),
and "Output 5"/"A3" (Cab Light) respond to the required "F-key" Input commands...

Given what you've learned above, I would hope you've already worked-out that 3-wires
(Red, Black, and White) are not-enough for even a basic DCC "Motor only" install,
which means that the Atlas locos you are looking-at are either Analog (NOT DCC-equipped),
or have some hard-wired connections you are not seeing/identifying...

In the DCC world, the BLUE wire is explicitly and specifically defined as "Function Common (+ve volts)",
so Yes, "U+" can be safely assumed to be "the Blue Wire"...
(Unless someone has done something very silly, and Very Not-DCC-Spec!!!)

See above, although the term "Function Slot" does not match any known DCC terminology?

What we can say is that, for each individually-behaving Light/LED,
there must be a matching discrete physical Output (color) Wire.

Um, close, but not-quite:

- YES, the Front Headlight is "F0f" (NMRA DCC Term) / "0f" (NixTrainz DB term)
- YES, the Rear Headlight is "F0r" (NMRA DCC Term) / "0r" (NixTrainz DB term)

- NO, in the NMRA DCC world, the Headlights are NOT the Red or Black wires!
(Again, if you have a loco which claims to be "DCC Ready" or "DCC Equipped",
and yet uses Red or Black wires for ANY of the Headlight or Function Outputs,
then someone has done something very silly, and Very Not-DCC-Spec!!!)

See above:
- the Headlight ("F0") function key on your DCC throttle simply sends a "F0 ON/OFF" command to the Decoder
- The Decoder recieves this "F0" command,
- the Decoder reads the "Current Direction" state,
- then enables the appropriate "Output wire" in consequence
(IE One "Function INPUT" is routed/mapped by the Decoder config to control TWO "Output wires")

- The Cab Light (Which Function key?) on your DCC throttle sends a "Fn On/OFF" command to the Decoder
- The Decoder recieves this "Fn" command,
- then enables the appropriate "Output wire" in consequence
(IE One "Function INPUT" is routed/mapped by the Decoder config to control ONE "Output wire")

- The DitchLight (Which Function key?) on your DCC throttle sends a "Fn On/OFF" command to the Decoder
- The Decoder recieves this "Fn" command,
- then enables the appropriate "Output wires" in consequence
(Simply turns any "Ditch Light" configured output ON or OFF)
- When the HORN (usually F2) command is received by the decoder,
it invokes an "flashing" mode on ANY OUTPUT which the decoder thinks is a "Ditch Light",
with ALTERNATE flashing for LEFT and RIGHT "ditch lights"
(This is why the TWO Physical Ditch lights each need THEIR OWN individual Output wires,
a SINGLE "Ditch Light Output" wire feeding both bulbs/LEDs would mean they could only flash TOGETHER,
not ALTERNATELY...)

I hope this helps...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Deep diving

is right Professor. After reading your explanation I may have to go to helmet diving on mixed gases to stay down that long.

Thanks very much for that extensive -  hopefully initial - evaluation of my project. I will attempt to elaborate though the danger has been that the more I explain the more I need to explain until I've written a model railroad version of War and Peace.

My name is Kent. That usually shows up on my signature block but didn't, so I went back and did that again and saved it.

This was also true for me. This was my first sound loco and it was good enough in all respects except for crossing my unpowered frogs which caused it and me grief. So I thought I will just install a current keeper and all will be well. But where? The board is dated 2011 and so I guess precedes the plug-in version of current keeper. Everything else on the board is plugged in.

I could find no place to put current keeper but knew that Decoder Buddy had easily visible spots. At the same time I had done a speaker install and plugged in a 21 pin Tsunami2 in a different locomotive. This revealed that a superior motor control and better prime mover sound was available. So I put those ideas together and decided to update this GP60 to have Tsunami2 and Current Keeper.

I want to take your observations and questions in order but have to clear up about the Atlas locomotives because it is part of the context for all my wire discussions. I have three, DCC ready, GP40-2 locomotives:

They all look like this inside (I did the speaker installs, they came without):

I was wrong about the wires as there is in fact a 1/2 inch green wire from the front LED board to a nearby plug, but there are no other colors than what you see. They have no blue wire, anywhere. Nor yellow, etc. They run great and all the functions work with that Tsunami2 21 pin decoder in there, but Atlas appears to have eschewed several NMRA wire color standards.

That comes into play later as the Walthers locomotive seemingly arbitrarily changes 4 of its wire colors enroute with splice jobs. This includes the grey motor wire being spliced to orange half way to the board and vice versa!

I'll have to come back and need to be excused at this point. In keeping with the theme of electrical issues, my vehicle is due at the shop to have its electrical problem analyzed.

Thanks for your patience and I will try to take up where I left off.

Multi colored wires part II

Dear Professor,

I have returned to help you help me isolate what I need to do next, I hope.

Got it. That helps. The decoder will tell which wires to activate though they will be on individual function tabs of some kind, not physically combined on one.

The way this thing is wired makes it a bit difficult to reconcile some of the wiring knowns. The rear headlight is an LED board that has only two wires coming from it, red and black. They plug into the control board at the front position labeled BL. You can see it on the first photo. No yellow.

The yellow wire, and the violet, seen on the plug in first photo; both are spliced halfway into black wires that continue each one to a separate ditch light plug. A brown wire comes out of each of those and goes to the small control board up top.

Blue, green, brown, and white continue in same colors also to the small control board as shown in 2nd photo.

I don't know if this matters much, but right now F0 is both headlights, F5 is both ditch lights (they do not operate independently), F6 is number boards only.

I do see that for this application, blue to U+ is going to be correct. On the rear LED board, since it has two wires independent of all other wiring, it must mean that red=blue and black=yellow for wiring purposes, and connected to those function tabs on the control board accordingly.

Remember that the existing yellow wire turns to black halfway and goes into a ditch light plug, so doesn't seem to have anything to do with rear headlight.

 Do you think that six wire plug is just where they are drawing power, and the actual (on/off) function control is within the small board shown in 2nd photo? All six of those wires (color change notwithstanding) leave the plug and terminate (directly or through a ditch light plug) on that small top mounted control board (2nd photo). That might mean that connecting them to the function board on the buddy would confuse the situation even more. Might that put the two control boards in conflict? 

My explanations may be adding to the confusion at this point rather than helping to illuminate, but your comments have made some things more clear to me.

I could put this all back together and let it ride, but I'm aiming to improve all my modeling skills...if you know what I mean.

Sidenote: OEM ST decoder and adding-a-KA

Dear Kent,

Just a quick sidenote before we jump back into the fray:

...ah, unpowered frogs, never a good idea...
(microswitches are cheap and simple, cross-compatible with both Analog and DCC,
and with AWP locos, should alevate most pickup issues before a "tactical patch" SA/KA/CK is required...)

When it comes to pre-"plug in KA" decoders, arguably the best guide to finding where to point the soldering iron is Marcus Amman's "Main North" DCC page
http://www.members.optusnet.com.au/mainnorth/alive.htm

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Chasing wires

Dear Kent,

Ah, the fun of OEM wiring...
(You can see why many modellers take the "rip and tear" approach rather than trying to knit old-and-new-together...)

anywho, in order of appearance...

Kinda makes sense, "BL" is common shorthand for "Backup Light",
aka "Rear Headlight". If Walthers have elected to save $ on the internal wiring by wiring eveything from the OEM ST decoder's connectors with red/black pairs, then we have to observe-closer to determine "what comes/goes where"...

...but that "6-wire loom" certainly looks like it's wired to DCC "Function Output" color spec to me...
(If the HL and BL are connected direct to the Decoder, then where does the 6-wire loom fit in?)

...at this point, any info is good info, as long as we keep it solidly in "diagnostic context"...

Just to confirm,
- F0 ON + DIR : FWD = FRONT Headlight ON/REAR Headlight OFF
- F0 ON + DIR : BKWD = REAR Headlight ON/FRONT Headlight OFF

is this correct?

We do NOT expect BOTH FRONT _and_ REAR Headlights to be ON/at-common-brightness by default,
IE the decoder seeming to disregard the current DIR(ection) state...
(...Unless you got this loco 2nd-hand, and someone has messed with the decoder CV settings already?

IE "Rule 17" lighting mode can Look Like "both Headlights are ON" at a common brightness when the loco is Stationary, Irrespective of the current "Direction setting",
with the "leading headlight" getting Brighter when the loco starts moving...

...but it's Very Unlikely to have a loco "ex-factory" ship with "Rule 17" headlight mode enabled by default....)

F5 may well turn both Left and Right Ditch-lights ON or OFF,
(IE looks like "One F-key controls both lights)

but if you have them ON (F5 = ON),

and then blow the Horn (Typically F2 on a factory-default ST sound decoder),

do the ditchlights Flash for a period of time?

If YES, and they flash alternately

IE Left Ditch = ON, Right Ditch = OFF
Left Ditch = OFF, Right Ditch = ON,
repeat ad nauseum

then the individual ditch lights absolutely must be fed by physically seperate outputs/wires
(and thus, would be seperate colors, IF the install followed correct NMRA wiring color code)

NOTE! Even if, in the current setup, they do NOT Flash when the Horn is blown,
they are still likely wired with the ditchlights on seperate outputs/wires,
as "alternate flashing ditchlights" is a commonly modeller-desired behaviour,
(even if the specific prototype ditchlights did not flash...),

and having them "pre-separated" in the physical/electrical domain means "adding flashing" is only a simple CV tweak away...
(If Walthers wired them "both ditchlight LEDs on a single wire output",
then the ability to "turn on alternate flashing" would be impossible,
which would be considered by many modellers to be an unjustified limitation of the model).

Good to know...

...but where does that leave the "cab light"?
(or, is the "cab light" just bleed from the "number board" light source?   ).

Given the other "what the?!?!?" things we're seeing, I'm loathe to assume that

NMRA-spec "Blue" wire = Function +ve
Red is usually used for +ve volts
Therefore, "NMRA Blue" = Walthers Rear-Headlight "Red"

(logical, but not something I'd blindly bet the life of a fresh paid-from-my-own-wallet decoder on)

but a few seconds with a multimeter should confirm with confidence...

Confusing, but OK...
(This is the first time we've had mention of the actual ditch-light wiring color?)

No, the 2nd board does not appear to have any "smarts" on it from the pics provided, just resistors.
All of the "On or Off" smarts is definitely directly under the control of the ST decoder.

I do have to wonder though, I see a "Rotary" label on that little board,
and a check of the ST and Walthers sites suggests the GP60 came with a Rotary Beacon?
What specific Walthers Part # is this loco?
(or failing that, what roadname/number/paint scheme?)

I think what we can say with any certainty is that, while that 6-wire loom looks to be wired per NMRA spec,
it's doing to take actual manual wire-chasing to confirm with any confidence exactly what goes where...
(pass the multimeter...)

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Clues...

Dear Kent,

Some documentation clues for reference...

https://soundtraxx.com/content/Reference/Factory-Installed/Walthers/Diesel/walthers_ho_gp60.pdf

Hint: check
CV39 and 40 (Function mapping),
CV49 - 52 (Function Mode)

Use https://soundtraxx.com/content/Reference/Manuals/Tsunami/tsunami_diesel_technical_reference_0213.pdf
/> to interpret the Values for each CV listed in the GP60-specific doc...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Look at the locomotive and....

there are two wires from the front truck and two wires from the rear truck.  The truck wires come from the left side or the right side of the truck and must be kept separate, left to left and right to right.  Two wires come from the motor and may or may not make the locomotive go in the correct direction.  They can be changed easily at a later time.  Two wires from each speaker.  If more than one speaker is used it is important to know about polarity.  
 

Now the fun detective part.  With a 9 volt battery that has a 1000 Ohm resistor in line make all the LEDs light.  Depending on the person who assembled the wires and the colors they had available that day, you might be lucky and find the blue wire is the + side and the rest of the wires when connected to the -side of the battery light up.  You will not hurt any LEDs with the battery/resistor combination if it does not light an LED.  
 

At this point you should be ready to rewire the locomotive.  The locomotive may go backwards when told to go forward.  Change the motor wires and that will fix the issue.

Larry Linger, Solo Contracting on YouTube has some absolutely excellent decoder installation videos that I recommend most highly.  Here is his latest to test drive.....  https://youtu.be/RmbPOLgnmYk. 

Hope this helps.

Progress

Dear Professor,

You are a man of admirable patience. I believe your line of questioning has steered me in the right direction and motivated me to check some things further. Many formerly arcane things are falling into place.

Along with Nick's 9 volt test regimen I think resolution is near. Nick, I saw that LED installation post you did on MRH and wondered if that would be something I could try for this problem.

In my second photo one can see there is a protective film over the solder points for the six wires. I was hesitant to mess with that but in the interest of mankind I pulled it off. It flaked away as ancient substances sometimes do. Underneath there are labels which provide further useful clues. I think.

From front to rear on the board, with wire color as soldered to each:

H+, empty

DLL+, brown wire (goes to left ditch light plug, black wire leaves plug, gets spliced to yellow, goes to six wire loom)

DLR+, brown wire (ditto to right, black wire leaves plug, gets spliced to violet, goes to six wire loom)

P7, blue wire (goes to six wire loom) (loom, good word)

Rotary, green wire (there is no rotary beacon on the engine, goes to six wire loom)

Num, brown wire (goes to six wire loom)

Head, white wire (goes to six wire loom)

To your latest:

- unpowered frogs. I haven't learned much about that yet and was leaving it alone because I 1) didn't want to mess up my nice scenery pulling track and 2) the other 4 locomotives sail through the switches no problem. This is the only engine to balk.

- Marcus Amman's "Main North" DCC page. In all my web searching for such things I never found that. Now bookmarked.

Exactly. Where indeed?

Affirmative.

- flashing ditch lights with horn. Did not check that specifically and can't remember, but in any event it's clear as you've noted that each ditch light has its own solder pad on the small control board. As you say, I expect CV programming would deal with it if wanted. I don't plan to reassemble just to check that.

Yep. Exactly right. The F6 is number boards and there is no actual light just for the cab.

 This is really good to know and makes a lot of sense when you describe looking at it in that way.

It's this one. https://www.walthers.com/emd-gp60-tsunami-r-sound-dcc-union-pacific-r-2005-ssw-tm-patch

I got a good deal. I think it was on the shelf for years. The Walthers/Soundtraxx decoder is labeled year 2011 on the back.

- documentation. Check. Good to go with all those documents. I've been through them. They do not provide actionable drawings or information particularly germane to my wiring project.

If blue really is U+, then I should be able to check each other wire with Nick's 9 volt field testing unit, then attach to decoder buddy according to function number, right?

Nick, if you are still here do I need the 1000 Ohm resistor given that you looked at the LED boards, verified the presence of individual resistors, and sent me a "0" Ohm Decoder Buddy, or can I just direct test since the resistors are accounted for?

Thank you gentlemen, for your time.

Sidenote: Walthers GP60 pickup issues

Dear Kent,

Just a sidenote:

Adding microswitches (or Frog-Juicers, if you're a pure-DCC layout and have the $$),
does not require wholesale lifting or replacing of entire turnouts,
unless the turnout itself is a Plastic Frog unit (IE can never be powered).

Further, assuming the turnouts you have are already metal-frog units,
adding a frog-wire and feeders to your track buss is a simple wiring task,
(I mean, dang, if you were/are considering the SMD-level soldering required to do a non-plug-n-play KA install, or replace a OEM ST decoder, then the "human hand sized" track soldering should be a doddle!)

and can be "stealth" installed using basic hand tools...

This concerns me greatly, as a "only one loco in the fleet has a problem" symtom really is a call to check the basics on The Specific Loco-in-Question as a First-Option,
rather than "patch over the issue with a KA" or "rip and tear" the guts out of the loco.

Walthers/Horizon-era Athearn/Proto2k diesels are known to frequently have excess lube/film on the contact-plates, leading to "iffy" wheel<> contact-plate contact. The contact plates also can use small plastic "pickup wire retainers" rather than actual solid solder joints. Cleaning the contact plates and wheel-surfaces of excess ex-factory lube and checking/soldering the pickup wires to the contact plates can be a "simple quick user fix",
which eliminates the fault-condition, and avoids massive (and commonly un-necessary) rebuild projects.
(something about "throwing baby out with bathwater" x "kill a mosquito with a howitzer" comes to mind).

Indeed, simply casting an observant eye over the "basic power paths" could well uncover a "30 second break/fix" situation which changes your entire opinion of this loco...
(take THIS thread, https://model-railroad-hobbyist.com/node/38895
/> which will live in hive-memory as a classic example of an entirely-predictable root-cause fault condition GOING UNDETECTED for Waaaaaaaay Tooooooo Looooong, due to lack of Basic Observation!)

ST decoders are not generally known for "finicky" behaviour, unless there is some underlying issue between the rail and the decoder (IE the Pickup power path),

and those pair of large silver capacitors evident on the board already give a measure of "Keep Alive" protection...

...if it's not too late, I really would reccomend taking a step-back from the soldering iron,
and taking a good look at the Basic "power pickup path" from all-wheels thru the contact-plates and pickup wire feeds, to the decoder...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

PS not to harp on too much, but I really implore Everyone to Read and Heed that thread linked above,
it is an object lesson in sooo many ways...

Progress cleanup

Dear Kent,

Gotta say, you're really kicking goals here, and that's heartening to see, Well Done!

In order of appearance:

'tis amazing what one might find hidden under blobs of hotglue and suchlike...  

Interesting...

- Given that we've already established that that "Rear Headlight" has it's own direct-connect Red/Black loom from Decoder --> Light, it would seem that the "DCC 6-wire color loom" has "shuffled everything up one",
thus "repurposing" the (typically F0r/Rear Headlight) Yellow wire for the Left Ditch Light (DLL)...

From a typical electrical-engineering P.o.V,
I guess this makes sense, you "save a wire" and use a "standard part",
but from a "User Reverse Engineering" P.o.V, repurposing what are commonly "specified and known" wire colors for "alternate tasks" can make for serious confusion...

It also kinda makes sense insofar as all of these outputs/lights are heading from the decoder towards the Front of the loco, (bundle them all together, they're all heading the same way),
while the Rear Headlight is "headiing off on it's lonesome" towards the Rear of the loco shell...

- Given this new info, I need to revise my previous wire-color "truth table" for this particular loco

Task                         "6-wire loom" Wire Color      DB Aux board terminal   F-key On/Off control
Front Headlight        White                                     0f                                       F0 (+ DIR = Fwd)
Left Ditchlight           Yellow                                    A1                                      F5
Rotary Beacon(?)     Green                                    - (Not Connected)
Right Ditch                Violet                                    A2                                       F5
Number board          Brown                                   A3                                       F6

- BTW, I'm intrigued by the nomenclature "DLx+", that "+" may lead someone to think that it's a "+ve Volts" feed... which doesn't necessarily make sense. The Yellow and Violet wires are typically "-ve" discrete outputs,
with the "+ve feed" being common to both Ditch lights, fed from the Blue "Function Common" line...

...but now that you're gettng comfy tracing out the wires and testing-for-polarity, I'm sure you'll work out "which wire is what polarity" in short-order...

Um, respectfully, they actually do. Maybe not "wire color <> light function", sure,
but they help flesh out the "F-key --> Decoder --> Physical Output" mapping that you'll need once the soldering-iron is powered-down...

- The "walthers_ho_gp60.pdf" gives the "ex-Walthers" CV default values,
admitedly sans-context, but when you start from zero, any info is good info...
- ...and the "Diesel Tech Reference" allows you to look up the CVs, provides context for each one,
and interpret the "ex-Walthers default values" in context.

First, let's get something perfectly clear,
for as long as there are MiniBulbs and/or LEDs used for Lighting,
there MUST ALWAYS be a resistor-per-bulb/LED in circuit...

No Ifs, Buts, or Maybes... This files under "Rules to Live By"...

I suspect that Nick has provided a "Zero Ohm" DB on the basis that:
- the "little board" has Resistors
- If the new decoder wiring config is

Decoder 21-pin Output line --> DB motherboard (+ "Zero Ohm" Aux board) --> "little board" (inc OEM resistors) --> Bulbs/LEDs

then the Rule "Thou Shalt Always Have Resistors in Circuit" is obeyed, 
and all should be well...

Now, IF you REMOVE/OMIT the "little board" from the circuit,
and wire the various bulbs/LEDs direct to the decoder (via the DB),
then there will be NO resistors (using the "Zero Ohm" DB option),
and those "once-worked OK" Bulb/LEDs will have a Short-but-Really-Bright life...

This is Important, because randomly-probing around on the "LED side" of the "little board" with a "fresh out of box" 9V battery poses Exactly The Same Risk,
IE "I was just testing" = "dammit, all bulbs/LEDs are now blown up".

THIS is why Nick reccomends 

Probing around directly on the bubs/LEDs with a 1000Ohm-resistor-equipped battery is "safe",
and if you happen to be probing around one the "decoder side" of the "small board",
the worst that willl happen is that the bulb/LED will only glow very faintly 

NOTE! while we're focussing on the "little board" and it's resistors,
we've already established that the Rear Headlight is seperate, on it's own 2-wire Red/Black "loom",
with no obvious Resistor in circuit. 

Now, I would suspect that the Rear Headlight resistor is actually located somewhere on the OEM ST decoder board (IE upstream from the small white "BL" connector),
but again, if you 
- remove the OEM ST decoder,
- and use the "Zero Ohm DB"
(because the majority of lights on the loco are routed thru the "small board" and it's resistors)

then you Will Absolutely need to manually add/install a 1000Ohm resistor for the "Rear Headlight",
in addition to the "small board"...

Looking forward to seeing your progress...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Clean up continues

Dear Professor,

Thanks for the latest.  

 I should put this on the list. My modeling pattern is the possibly classic, train set> DC layout> DCC conversion> DCC with sound> not sure what stage is next...

So I come to things one after another as a perpetual rookie. I've seen photos of switches with one wire hanging down from the frog and you're right that I could manage that, but then what happens to the one wire? Where's the other one? Do I wire it to an existing track wire? That doesn't sound right, and sure enough it isn't. One needs microswitches, or juicers, or something I just haven't looked into yet. I'll probably hit you up on that one someday. 

Yes. I had seen some reporting about this along with cracked axle sleeves so I checked all that. This loco has nice metal, helical gearing with no issues, but did have a lot of old grease in there and on the contacts that I cleaned out. I suppose that helped but wasn't enough to make the problem go away. Nevertheless you have inspired me to look at all that one more time just to be certain.

 Given all that we've covered so far this has bothered me. I was looking for that blue wire to end at something with (+) on it, and all I get is P7. Not helpful. Then the yellow and violet going to ditch lights DO END at a (+) instead of a (-). It all leaves a shadow of doubt.

There also was not much wire saving if the green one goes from doing nothing at one end to doing nothing at the other end. I guess it is always there to be energized if needed for a loco that does have a beacon.

I don't want to portray the documentation as though it is not useful, but I have read all that and I understand what I'm being told. I can and have programmed CVs, used the calculators, get the picture on all the interrelationships, etc. I suppose what I was hoping for was one simple schematic drawing with labels of my decoder board that would have shortened the war, saved thousands of lives, etc.

It's been awhile and a lot of words at this point, but I noted upstream that the rear headlight does have its own little board with resistors incorporated. Still, your admonition is sound. I should just go with a resistor in the path regardless, so as to be safer than sorrier.

I heard it from you first, and that's the plan.

This locomotive is loaded with potential cautionary tales so in that respect has been a good one to learn from. Painful though. If everything under the shell looked like it's "supposed to", the project would have been too easy with little new having been learned.

I understand the broader theme too. Power your frogs, ensure good electrical path inside locomotive, T1 factory decoders are not bad, the engine does work ok so is this trip really necessary?

Now that I'm fairly confident I can pull this off maybe I won't.

People around here are usually not so young anymore so maybe they remember The Three Stooges? Lot of good one liners there, to include "don't you dare hit me in the head, you know I'm not normal".

Thoughts

Dear Kent,

As the thoughts occur:

I guess I can see "P7" being some reference to "Positive, splits 7 ways" (IE "common connection"),
but I absolutely agree with your, it's a weird nomenclature where much of the rest seems at-least vaguely logical...

More likely, it's "one loom, which handles all variants of the model" production/assembly saving,
and is cheaper/less-error-prone in assembly to "just leave the Rotary Beacon wire unterminated if the model doesn't have a Rotary", than have 2x explicitly-different "lighting looms"
which need to be correctly selected/installed ex-factory to suit the given model-in-question...

< FFwd some years from now, in a Model RRer's bar somewhere,
Prof passes Kent a Libation of Kent's choice,
wraps an arm around Kents shoulders, 
and laugh-slurs into his drink...
"...you remember, ha ha, that one time, te he he, you know,
when we firsht looked inside a model loco, har har har,
and phought that there would actually be some ushable wiring schematic documentation provided?
I mean, what were we thinking?!?!?! LOLOLOLOL!!!!..."

Seriously, rest assured, we've all been there...
...most modellers take the approach
"..it's not worth the time to Reverse Engineer, just take it back-to-bare-wires, and start from scratch..."

FWIW, stash this one in your "Useful Bookmarked Webpages" 
https://tcsdcc.com/installations
/> https://tcsdcc.com/installations/wowsound

Happy Modelling,
Aim to Improve,
Prof Klyzlr

. . .

Here is my solution for testing leds.

This is  a couple of dental floss  boxes, .30thou stiff music wire and a CR2032  coin batt. The CR2032 has sufficient internal resistance  for this use.

Perfect  led tester.  No need for a  resistor or other gizmoes.  And the long leads can act as probes or tweezers.

This also helps determine if a resistor IS present in circuit.  Probe one end of loom, if led does not light but does if you probe direct at the led, you know you have a resistor present somewhere.

Marc

MRH is a great place

Joe Fugate has done a real public service by creating this venue, where people that know will share with people that don't.

Thank you Professor K for your time and attention to detail in helping me understand my current undertaking. Thanks into the bargain to Nick of Nixtrains (outstanding website, dude) for the advice and review of my circuit boards, and Marc for that cool homegrown testing apparatus. I have to put in a plug here for George Bogatiuk at SoundTraxx too, who never hesitates to answer the call of "what do you think about this?" when the subject involves SoundTraxx equipment.

Professor, I've seen your commentary many times at MRH and I really appreciate your methods for problem solving. Thorough. One hesitates to lay out everything in an initial post about an issue because - TLDR, but you keep driving until it's all out there.

The pros here freely share what they've learned, which makes the hobby more enjoyable and probably expands it; but sometimes they've learned so much over the years that they tend to forget what it's like to be ignorant.

You have sympathy for the ignorant and I'm grateful.