# 751 D switch



## rph (Mar 1, 2021)

Installing 751 D switch from Ken Stapleton for dc ho system The switch (Atlas snap switch) works fine but can't get the LED lights in dwarf signal to work. Bought dwarf signal off Ebay; two aspect red over green, have three wire leads with resistor on common lead, said they are prewired to work with 9-12 volt dc. Am using a 12v dc 3A transformer to power switch. Am I using the wrong type of LED, if so which ones should I use and where do I get them? 
Thank you
Ron


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## DonR (Oct 18, 2012)

It would seem that
the power source you describe would be correct for
751D and the dwrarf signal that you have. if
it's not working there is a wiring error somewhere.

You should recheck your Dwarf signal manual
to determine whether the common that includes the
resistor is negative or positive. If negative, connect
that to DC source negative wire... the
the positive source wire should go to the center tab
on the 751D (check it's manual for wiring). If the dwarf
common is positive, connect it to source positive,
then the negative wire would go
to the 751D center tab.

In either case, the other two drarf wires go to
the outer tabs of the 751D (see manual) Check to see which wire
is Red so you get right aspect when points throw.

Don


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## rph (Mar 1, 2021)

DonR said:


> It would seem that
> the power source you describe would be correct for
> 751D and the dwrarf signal that you have. if
> it's not working there is a wiring error somewhere.
> ...


Don, 
Thanks for getting back to me. I bought the dwarf signals off Ebay so there was no manual and I don't know if the common is negative or positive The 751 D switch has a wire harness, no manual but a circuit diagram which I don't understand. The signal came with a red and a green wire and a black wire with a resistor which I assume is the LED ground. I followed the 751 D instructions for the colored wires: violet to led a, blue to led b, green to led ground, orange to supply ground, yellow to supply 12 v, white to coil common, red to coil a, black to coil b. The snap switch will work but the led lights don't.
At this point I don't know enough to know what to do next. I would greatly appreciate any suggestions and help you can give me.
Thanks Ron


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## DonR (Oct 18, 2012)

Ron

We'll take one thing at a time.
First the drarf signal. We have to know
whether the black wire should get positive
or negative connection.
You can easily
check it's wiring plan with your DC
source. Connect the negative DC source
wire to the Dwarf black wire with resistor.
Use a wire from the DC source positive.
Touch the Red Dwarf Wire. Does it glow?
Touch the Green dwarf wire. Does it glow?
If they glow then the Black wire should be
connected to the DC source Negative
Then we move on to how to connect
to the 751.
If they don't glow, then:
Connect DC source Positive to the dwarf black resistor wire.
Use a wire from the DC source Negative.
Touch the Red Dwarf wire. Does it glow?
Touch the Green Dwarf wire. Does it glow>'
If they glow using the black wire as Positive
then we know how to wire the dwarf.
Let us know which connections worked.

Don


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## rph (Mar 1, 2021)

DonR said:


> Ron
> 
> We'll take one thing at a time.
> First the drarf signal. We have to know
> ...


Don,
When I connected the black wire with the resistor from the dwarf to the DC positive wire (red wire from transformer) the LEDs work. When I connected black wire with resistor to negative power source LEDs did not work. What's next?
Thank you,
Ron


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## DonR (Oct 18, 2012)

Your test shows that the black wire with the
resistor is the positive source for your dwarf. Therefore,
the negative DC source must be connected to the
middle terminal of the 751 light connections. The red and
green dwarf wires would go to the 2 remaining terminals.
I see that Stapleton has added a multicolor wiring harness
to the old 751. This, is a complication.
I couldn't find the color codes for this. Could
you show a copy of the 751 wiring instructions and a
close up of the 751 that you have. We have to be able
to connect the middle tab of the 751 light switch to the
negative DC source. That should then let the 751 flip 
the point, and light the red or green dwarf LED. Apparently,
now, that center terminal is getting the positive DC source
thus you lights don't work.

Don


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## rph (Mar 1, 2021)

DonR said:


> Your test shows that the black wire with the
> resistor is the positive source for your dwarf. Therefore,
> the negative DC source must be connected to the
> middle terminal of the 751 light connections. The red and
> ...


Don
Attached is picture of switch and all instructions received with switch. The wiring harness is aligned as it would be when attached to switch. As you look at wire harness, from right to left- violet, blue, green, orange, yellow, white, red, black. Hope it all comes through, if not I will get my son to help.
Thanks,
Ron


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## DonR (Oct 18, 2012)

I tried to enlarge the pages but the Forum system doesn't help
much with that.
So, let's just go with what we know. You have the device, and
the harness, and the table that identifies what each color wire
does. I believe the only wire we need be concerned with
is the CENTER tab of the 751 light switch section. Your DC NEGATIVE
should go to it. You should be able to identify it's wire in
the harness. From your past posts you have said that the
points work...and my guess is that you already have the dwarf
red and green wires connected to the 751 harness. So don't
bother with those wires of the harness. (you may have to reverse
these if the aspect doesn't match the points)

I think your whole problem was simply that Stapleton didn't know
that the dwarf signal common was Positive...it seems they expected it
to be negative. 
The 751 was simple to wire..,.this new harness seems to have
made it more complicated.

Give it a try and let us know.

Don


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## rph (Mar 1, 2021)

DonR said:


> I tried to enlarge the pages but the Forum system doesn't help
> much with that.
> So, let's just go with what we know. You have the device, and
> the harness, and the table that identifies what each color wire
> ...


Don,
Had a chance to try to get the 751D switch with wiring harness to work with the common anode, no luck, think I burned up the switch. I have sent two emails to Ken Stapleton asking for help but have not received any reply. Is this lack of response usual, or is he just mad at me for asking questions?
Could the switch work without the wiring harness, or is it only for common cathode LEDs?
Do you know anybody that got my situation to work, or has experience with Ken's products?
Where can I find common cathode LED dwarf signals? 
Thanks, Ron


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## vette-kid (May 2, 2020)

I had the 751K. Ken was very responsive and communicated a lot with me. Unfortunately I was never able to get them working and have moved on. I was excited about the prospect of them, but reality didn't match up. 

Sent from my SM-G781U using Tapatalk


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## DonR (Oct 18, 2012)

Ron

Stay in contact with Stapleton. We couldn't even guess
what has happened to your 751D. I suspect the wiring
harness has something to do with causing the problem.
There had been no problems reported prior to it's
coming on the scene.

Don


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