# Help with P1k Wiring



## Switcher (Jan 29, 2013)

Hi gang,

Recently I inherited an older non DCC ready P1k F3A and while I know that in itself is no big deal, it is like new, runs like a top and I just like it. There is one small hitch though. The he4adlight does not work. Burned out bulb I thought, easy fix so I popped the hood. There was the bulb alright but with both leads detached from the circuit board. Hmmm, so I took out the bulb and tested it at 1.3 volts and found it to burn brightly. Why the previous owner disconnected it I have not a clue. Problem is I don't know which tabs on the circuit board to hook it back up to. I attached a screenshot of the board. It seems as though tabs WH1, FL1 and/or FL2 would be the likely candidates as that end of the board is closest to the headlight. FL2 goes to the negative side of the truck. So I put about 5 volts on the board and tried every combination I could muster between the light bulb leads and those three tabs but nothing. So now I'm lost as to where to go next and decided to open it up to the membership to see if there is someone that knows a whale of a lot more about this than do I. Just wish they would label this stuff so it made some sense.

Would greatly appreciate any thoughts or suggestions. WB


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## DonR (Oct 18, 2012)

I know absolutely nothing about that circuit board...but I won't let that
keep me from showing my ignorance. It's always fun to
make guesses...so until one of the guys who knows what he's talking
about posts, I'm game.

What I see in your pic seems to be a 300 ohm 1 watt resistor and several
what appear to be diodes. The diodes could be used to light the
headlight only when going forward. 

You said FL2 is the 'negative' truck lead. Which is the 'positive' truck
lead terminal?

To what terminals are the motor leads connected?

1.5 v seems very low for an incandescent bulb on a DC locomotive, they
are usually 12 V. Is the bulb actually an LED? They usually are of that
low voltage But work only when connected correctly. The resistor could
be in there to reduced the voltage for the headlight and would be connected
thru a diode to light when going forward.
So if your test was made when current was in backup polarity you
would not get a light. 

A multimeter set to low DC voltage probing the terminals should
give you a clue; powering the unit so polarity can be reversed.

Don


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## Switcher (Jan 29, 2013)

Well, I sure like your enthusiasm and your willingness to jump in and "get your hands dirty". 

The positive side of the truck reaches all the way over and is connected to the other trucks positive lead. The motor is attached to the pads on either side of the board in the V.

The bulb is definitely a 1.5 volt. That was typical of Proto's prior to them switching to led's. And I agree with you. I think that 300 ohm, 1 watt resistor is the dropping resistor for the bulb. And the diodes are to stop the bulb from coming on in reverse. It just seems to me that pads WH1 and FL1 would be for the bulb. Yet I have powered the board with up to 5 volts and mixed and matched the bulb leads between all three of those pads and gotten nothing. I even tried reversing the voltage to the board but that didn't do anything either. That's why I'm so befuddled. 

Thanks for your input and I would certainly welcome any other ideas or theory's you might have up your sleeve. It might be interesting to see how this mystery unfolds. Well, that is, if it unfolds.

Jack


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## DonR (Oct 18, 2012)

Jack

That 300 ohm resistor could well reduce the voltage for
the headlight below what it takes to glow if you are testing
with only 5 volts.

I'd sure like to know the voltages you get on those terminals
even with only 5 volts. But better, feeding normal track
voltage which is nominally 7 or 8 volts up to 12 or so, DC.
But keep that lil bulb away while doing the test.

If you don't have a multimeter, get yourself to the nearest
Harbor Freight, they all but give them away most days. $3.99,
and for layout purposes that's all you need.

By the way, you mentioned that the bulb burned brightly at
1.3 volts, was that in or out of it's 'socket'? Does it burn
when the bulb is in place and the wires are on an AA or AAA
battery? Possibly the bulb is not making contact in the socket
or there is a short or open in the fixture wiring. At that low
voltage a minor bit of corrosion could break continuity. Think
of how flashlights dim and brighten when you shake them.

If the bulb doesn't burn IN the socket, remove the bulb and
test for continuity of the wires to each contact of the 'socket'.

There must be a reason the previous owner had disconnected
the wires.

Let's see how far the blind can lead the blind, here. 

Don


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## Switcher (Jan 29, 2013)

Don,

Well, right now it kinda is the blind leading the blind, eh?

Unfortunately the voltage is 0 at 5 volts as well as 12 volts for that matter. It's as if they were dead but I do get high resistance between the two on the ohmmeter so something's going on in there...I just don't know what.

This P1K doesn't use a light socket. It's just a bulb with the pigtails soldered to the wires and a piece of vinyl tube for insulation. That was a good troubleshooting call of yours though.

Yep, no doubt the previous owner disconnected the bulb for a reason and I think I'm experiencing that reason as we speak.

If worst case scenario happens and I don't find a solution I can always change to an led with a dropping resistor and wire in a constant intensity circuit. just didn't want to have to go to the added cost and hassle if I can avoid it.

Thanks for hanging in there with me.

Jack


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## rrgrassi (May 3, 2012)

For that matter, you could put in a DCC Decoder as well.

Do you have test rollers so that you can run the locomotive, and test for voltage to the headlight part of the board?

If no rollers, disconnect power to the motor and then test for voltage at the headlight part of the board.


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## Switcher (Jan 29, 2013)

A DCC decoder is of course a viable option but an expensive one compared to figuring out the two wire hookup for the headlamp. The biggest problem I'm facing is I don't know which pads on the circuit board to usefor the headlight bulb. Right now the circuit is out of the locomotive. When I apply power to the board I get power to the motor tabs but not to the tabs that go through the resistor and diodes, no matter how I configure the bulb wires or if I reverse the polarity. More and more i"m beginning to wonder if this circuit is broken. I was hoping to see if anyone knows the correct hookup for the headlight before I convert to constant intensity or a DCC decoder.

Appreciate your input.


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## DonR (Oct 18, 2012)

Jack

Studying that circuit board pic it appears to be nothing but the
300 ohm resistor and several diodes, all of which appear
to pass current in one direction, and one in the opposite.

Sure would be helpful to see the underside of that board to
see how they are connecting the diodes to the tabs.

Can you check the resistor and individual diodes for DC continuity or are
they in parallel?

Since the motor tabs get power, then both sides of DC are on
the board. I would guess that the resistor and diodes are in
one side of the circuit, thus there must be a buss for the other
side. What do you see? If that is the case have you checked
the buss AND the various tabs for headlight voltage?

You say the bulb burns with 1.3 v...that is thru those wires...thus that
would eliminate any short in that area...right?

Hey...this is more fun than Charades. 

Don


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## Switcher (Jan 29, 2013)

Don,

Ask and ye shall receive. Attached is the flip (bottom) side of the circuit board.

Since we are having so much fun (right?) with this, let's break down the traces on the flip side of the board, should we? So, this much we know: 

- The tab behind P7 is + power in
- The tab behind P6 is - power in
- The tab FL2 is also - power in 
- The + power in from the left hand truck crosses over the board and is connected 
together 
with P7
_ The motor attaches to the two tabs in the V of the board and they get power and they 
get power.
- The suspected headlight tabs are WH1, FL1 and FL2. 

Now here's where it gets interesting. I don't know how well you can follow the traces in the pic so here's what I see. One leg of that big 300 ohm, 1 watt resistor is soldered to the trace line of P7, which is attached to nothing. The other leg of the resistor attaches to two trace's, one to FL1 trace and the other to the cathode of the diode closest to FL1. So it now appears to me that neither the big resistor nor tab FL1 are being used on this circuit board.

Now for the traces:

- P7 (+ power) traces to the + motor tab and ends there
- P6 (- power) traces to the - motor tab and then connects with the WH1 tab. *So that
should make WH1 negative for the headlamp *
- FL2 has a trace to the cathode of the diode closest to the big resistor. 

Bottom line is I don't see where the positive power is getting to the diodes. The only point where positive enters this circuit board is at tab P7. It then dead ends at the + motor tab. I don't get it. Somethings still missing obviously.

The bulb burns brightly at 1.3 volts when powered by an outside power source.

Wow. What do ya think? Still having more fun than playing Charades? 

Jack


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## DonR (Oct 18, 2012)

La tee da...all the world is waiting for the sunrise...
Zippidee doo dah...burble burble...

And if you do that the light will burn....

Jack

All that makes about as much sense as this circuit board...I agree
with your traces of the thing.

To make it easier, I printed out your 2 pics.

I have no idea what they had in mind. Apparently it was made to
use in various locos by using jumpers. 

But, it looks to me that if you put a jumper between P7 and
the adjacent tab that connects to the resistor you'll have the
missing + feed. Thus the headlight tab F2 would be powered thru
the resistor and the diode next to the resistor, the other wire, as you noted, to (-) WH1. (I can't see a direct 'power feed' to F2 but
correct me if wrong, looks like it goes thru diode)

FL1 with WH1 would seem to be a 'non directional' l.5 vdc. (cab light?)

Try with your meter and see if you don't get a voltage
on each of the 2 pairs of terminals. F2 would light headlight only when going forward.

I wouldn't connect that fragile 1.5 v bulb till it's all settled.

Meanwhile, even tho only 12:35P, I may need a mighty potent
libation to overcome the swirling electrons in my reeling noggin. 

Don


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## tr1 (Mar 9, 2013)

*tracing electrical pathway,trouble shooting ?*

I did not know that.


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## Switcher (Jan 29, 2013)

Don, 

Sorry for the delayed reply. I was tied up today to witness my beloved Huskers get destroyed by Michigan State. I just keep telling myself it's only a game, its only a game but, help it does not. The only remedy that does seem to help is a concoction of 5 parts Dewar's and 1 part soda water and I find it usually takes more than one to ease the pain.

Back to business. Yes, I wholeheartedly agree this board is designed for more than one type of locomotive which probably includes road switchers utilizing front and rear headlights.

And you would be correct sir. I powered up P7 that traces through the resistor and ends going into #3 diode. While that does complete the circuit to FL1 it only reduces the voltage from 12 to about 10. So I thought hmmmm, maybe it needs a load so I dug out a 12 volt mini bulb, tested it to make sure it worked and tried it in my make shift circuit. Wouldn't light. A 12 volt bulb should ignite with 10 volts, don't you think? Put the multimeter back in. It registers 10 volts. So now I have created a phantom circuit. Oh boy. Now what?

With regard to F2 and the diode. It is impossible for me as well to see if it is connected to a diode as the trace is obscured by all the diode bodies and by another trace super imposed over it but it appears that it is connected to a diode.

My mind is slowly but surely beginning to turn to mush over this circuit. It seems I have tried every conceivable combination of wiring with zero results. Frustrating. Ahhhh. I can tell it's time for another one of those concoctions. Care to join me?

Jack


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## golfermd (Apr 19, 2013)

Switcher said:


> The only remedy that does seem to help is a concoction of 5 parts Dewar's and 1 part soda water...


Why so much soda?! I really like Dewars on the rocks...


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## Switcher (Jan 29, 2013)

You bring up a valid point golfermd. For me, the "one part" is adjustable to a splash, on the rocks or straight up. It all depends on my mood at the time. Bottom line is any of the above combinations will help you arrive at the same destination, it's just a matter of how quickly you wish to arrive...


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## DonR (Oct 18, 2012)

golfermd said:


> Why so much soda?! I really like Dewars on the rocks...



Mine is a socalled vodka martini...(actually it's almost pure
vodka).

Jack

For untold decades I have used multimeters...and it was GunrunnerJohn who
had to set me straight on reading voltage after a resistor in an UNLOADED
circuit. You do get an incorrect meter reading unless there is
a load on the resistor.

Check your FL1 with the multimeter again with the 12 v bulb connected. 
You should see something less than 1.5 volts. If it is...winner!

Also, then, check FL2 with the 12 v bulb and meter.
Since I think it is thru a diode, you may have
to reverse your 'power in' wires to get the 'forward' polarity. 

If that also shows around 1.5 volts, and goes off when you
again reverse polarity, you would connect your actual 1.5 v bulb
wires to WH1 AND FL2. Bigtime winner!

I see the fat lady rumbling onto the stage, so I hope this puts
the finale to this opera. It's been fun.

Now I have to go and see what I can do to push our
Jaguars to win over the Arizona Cardinals today.

But if things still not kopacetic run the curtain up again.

Don


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## Switcher (Jan 29, 2013)

Don,

Eureka! I struck gold! WH1 and FL2 were the magic numbers along with running power through P7 to complete the circuit. Could not have done this without your help my friend. I'm afraid I would have given up were it not for your persistent determination to see this through. For that I am forever indebted to you:appl:.

I have only been in Jacksonville once. Very nice town and one in which I could certainly live in. I regret for not having known you then as I would have liked to stop by to shake your hand and perhaps share in one, two or maybe even three of those vodka martini's...on me of course.

So with that, the fat lady has sung, the final curtain has dropped and brought this saga to an end.

It was fun, challenging and I hope to run into you again on the forum sometime. Hopefully if I do, it will be me returning the favor to you. Thanks again,

Jack


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## DonR (Oct 18, 2012)

Enjoyed the challenge.

Now, if only getting the Jaguars on a winning streak were
that easy.

You know things are bad when Bill Oreilly uses a Broncos vs
Jaguars analogy to illustrate how poor MSNBC is
compared to Fox News. Aaaargh.

Don


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## Switcher (Jan 29, 2013)

It's frustrating, believe me, I know. Have faith...things will get better. 

Jack


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## ggnlars (Aug 6, 2013)

Basically, the light board is to give you directional lighting. These boards are similar to the long flat DCC decoders. The truck power wires attach to the out side pads. Left side truck wire to the left side pad, etc. The two side pads are the motor power points. The two inside pads on the end with four pads are where the light connects. I don't have the code for which wire goes left or right. If you connect it backwards it won't light. If that is the case just reverse the connections.

Larry


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## DonR (Oct 18, 2012)

Larry

Where wuz you when we needed you?

Jack and I traced it all down the hard way.

We had to discover what you knew.

We found that F2 and WH1 power the 1.5 v
headlight when there's forward polarity.

F1 and WH1 are always on with 1.5 volts.

Didn't see a connection for a backup light.

However, we don't have a clue as to
the purpose of the other diodes.

Don


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## Switcher (Jan 29, 2013)

Larry,

And you are right. The frame and weight on these is cast as one. I am used to working on P2K's where the weight is attached to the frame by screws so I just assumed the same would be true for the P1K models. Not. Makes it a little tougher to remove the trucks is all. It's like learning to ride a bike. Once you've taken one of these apart, the next one is a piece of cake.

Also appreciate the wiring scheme for this circuit board. As Don alluded to we seemed to have discovered the match up. In this case there is no need for a backup or rear headlight as it is an F unit. No doubt this same board is used for other P1K locomotives which require different wiring configurations as there are a number of other unused soldering pads.

Second opinions are always good for verification and this one in no exception. Your input and effort are valued and appreciated. Thanks for taking the time to respond.

And Don, thanks for chiming in. It makes my job easier.

Jack


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## ggnlars (Aug 6, 2013)

Don,
Sorry, I have been traveling and hadn't visited the site for several days. I actually drove past Jacksonville about the time you were discussing this. I spent a week in Sarasota and then drove to DC, and finally back to Indy. All for pleasure, but not much time to visit the site.
You did a great job of sorting thing out.
Larry


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## Switcher (Jan 29, 2013)

Don,

If you are still tuning in I just wanted to comment that while the loss to the Cardinals was I'm sure painful for you, at least the Jaguars came away with something. Jason Babin is now known as the Barber of Jacksonville. Oh my, that scalping must have been painful. Have a funny feeling we are now going to see a lot of that agoing on round the league.

Jack


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## DonR (Oct 18, 2012)

Jack

To watch the Jags play this year you have to well 
'lubricate' yourself before the game else you'll
be throwing things at the TV.

There was a measure of Run defense Sunday...actually,
both sides were pretty good at that.

I hear that the dreadlocks were sent to the man and he
plans to have them woven back into his 'do'.

I saw it when Babin came off the field carrying them...now it's become
an NFL must see. 

Don


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## Switcher (Jan 29, 2013)

Don,

One should well lubricate ones self prior to the kickoff of any sporting event, in my estimation. 

I, too, witnessed Babin parading about with the dreaded dreadlocks dangling from his paw. The real beauty was in the way he dropped them. Turned his hand upside down and spread his hand out kind of like he was dropping a dead rat or something. Go back and watch a replay if you missed that. And, yes, I had read the dreadlocks were returned to their rightful owner, Mr. Ellingsworth, who was quite lighthearted about the incident and pretty much said it is what it is and plans on having them interwoven back into his scalp. I would be very much surprised if they make it through the next game without being ripped out...again. 

Jack


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