Power supply for Railroad Signal

Trains Magazine General Discussion
1

I am restoring a 3-lamp signal for my grandson’s model train room. On teardown, it looks like the signal ran on low voltage DC? power. The bulbs inside are listed at 10V, 18 W. I am looking for an AC/DC power converter that I can plug into the wall and hard wire to the signal with throw switches to run the lights. Anybody out there work on these? Is it DC powered as I suspect? Any ideas on sources for a power pack-A/C-D/C converter? Thanks.

Millster

2

Just run down to Radio Shack and get a 12v transformer. Since its for your son’s room be sure its the “Wall Wart” type, ie: enclosed with a 110 plug already there.

John

3

Also make shure the power supply is of sufficient wattage to handle the load. If you plan on running all three bulbs at the same time you will need a 60 watt supply. Chances are you won’t find a wall transformer that will work, most are rated in milliwatts. Also if you are just running the bulbs then you can use AC, there is no need to rectify to DC.

And welcome to the forum. [8D]

4

Instead of wiring it with three toggle switches, consider a rotary switch of sufficient capacity. That way only one bulb will be on at at time, which will help you with your power issues. It’ll also be more prototypical.

The bulbs would be DC (although incandescent bulbs really don’t care all that much), since many signal locations ran on batteries (and probably still do as a backup).

I doubt a self-contained plug-in-the-wall transformer will work. By my math, you’ll be drawing an amp and a half or so.

On the other hand, an HO power pack might work…

5

Just walked over to a shelf behind me and there is a 12v 1amp transformer (wall wart type) lying there. I don’t think you will find to many 12v bulbs using 1 amp unless you are after large application type bulbs. The newer auto headlight bulbs come to mind. But you don’t need a large bulb in the signal anyway as the fresnel lens will amplify the light. Not sure what type of signal head you have but I believe most have bayonet type mounts. I’d take that to an auto supply store and see if they have a bulb that fits. Unless the signal still has working bulbs. If you live near me (Delaware Water Gap) I can help you fix this as I did a Drwaf signal some time ago (sold).

John

6

I’m going to assume you’re talking about a 3-light dwarf signal here? And I’m going to assume you’ll only operate one bulb at a time. Even though they’re rated at 10 volts DC (you can also use 12 V. car headlight bulbs with the right pin mount), do not run them at more than 8 volts…they’ll last longer that way! The bulbs pull around 1.5-1.8 amps depending on how bright you want them. Do NOT use a model RR transformer to run the bulb(s). Not only will the bulb only stay on for around 5 minutes before tripping the transformer, you could also burn up the transformer itself…permanently. Those things are simply not capable of handling such a load for extended periods of time. You can find some good heavy duty DC power supplies on eBay or elsewhere. A good one is not cheap however, so be prepared to spend a little $$$.

In the photos below, I’ve got a single searchlight signal plus the blue “lunar” aspect and a third (and fourth) bulb running together on a dwarf signal at the top of our driveway. I was fortunate enough to h

7

Nice setup !!! and nice pic Joe !!!

8

Here are some possible power supplies.

http://www.bb-elec.com/product_family.asp?FamilyId=394&TrailType=Sub&Trail=695

http://www.bb-elec.com/bb-elec/literature/MDR-20-spec.pdf

http://www.ab.com/en/epub/catalogs/12768/229240/1151309/1151313/tab6.html

9

While we are on the topic of rewiring railroad artifacts, I have a question.

I have my fathers telegraph bug (horizontal moving telegraph key), a standard telegraph key and a sounder ( the thing that clicks when you move the key) and I was wondering what kind of power supply will I need to make it work?

Thanks in advance.

AgentKid

10

Whatever voltage it takes to ‘click’ the sounder, try 12 volts DC. Then if that doesn’t work step up the voltage till it does. If you are not sure about polairity(+ / -)try both ways before you up the voltage.

11

Have an ex SOU three lamp cast iron signal. Each light box has its own transformer and hooked each transformer with 16 guage wire and it plugs directly into my 110v outlet.

12

Thank you Chad. By the way though, all three pieces use cloth wrapped insulation on the wiring, is twelve volts still going to be OK? The key and sounder are both very early twentieth century vintage and my Dad bought the bug in 1947. It was not standard issue equipment on the CPR. Thanks again.

AgentKid

13

How about using a low voltage power transformer for outdoor lighting… I think they put out low voltage AC but not sure.

14

AgentKid:

The wiring should be able to handle 12VDC with no problem, though I’m not sure about what the sounder needs. A quick way to find out is to get a model train power pack, start at 0V and turn up the voltage (throttle) until the sounder clicks - measure the voltage and use maybe 25% more to make the sounder work reliably.

I’m also guessing that the bug was made by “Vibroplex”, the bugs were also commonly used by hams.

  • Erik
15

Thanks very much Eric. I’ve wondered a long time about using a model train transformer. And yes the bug is a Vibroplex, and yes it was brought at Smalley’s Electric, the supplier to the ham radio community in Calgary for many decades.

AgentKid

16

Actually the model rr power supply is not a good way to determine voltage, most are current limiting and will alway show 16-18 volts reguardless of the setting. Plus model rr power packs have little if any filtering (except the $$$ ones).

17

I was proposing that he use the track outputs on the power supply as a way of getting variable DC voltage. Since the sounder is an inductive load, it probably doesn’t care about the 120 Hz ripple coming from the power pack.

When it comes to current, there’s a pulsed RF amplifier at work using a 4CX35000 for the final - filament power for that beast is 10V at 295A.

18

295 amps ??? or milli-amps ?

For AgentKid, why not call Smalley’s and ask what they recommend for a power supply for the bug ?

You may also find the following of interest:

http://www.faradic.net/~gsraven/telegraph_tales/drgw/instruments/tg_instruments.html

which is the “Telegraph Instruments” page within the “Electrical Communication Equipment Used by the Denver and Rio Grande Western Railroad” webpage; and also -

http://cs.trains.com/trccs/forums/p/130991/1473255.aspx#1473255

= thread on “Trackside Phones”, which includes some other links that I dug up. One of the other posts there by csxengineer98 says that he recalls a trackside phone box that used 4 “D” size batteries (which would be 6 volts). You may find it useful to check out the other links on the D&RGW site and the Telephone Tribute site.

Anybody else rem

19

I’d bet one or two 6 volt lantern batteries would probably cover your needs for the sounder. No 110AC to worry about then.

Edit - Just went out and searched telegraph power supplies myself. From what I can see, there was no “standard” voltage. The same site that suggested the 120VDC supply also had a schematic for a 30/60VDC supply.

It appears that the answer is “whatever makes the sounder work.”

20

Larry -

Just curious - which schematic was that ? Because I sure missed that ! Unless you’re “reading between the lines” and just using a portion of one of them ?

Just playing around a little with Fig. 2: it appears that he bases it on a current = I of 50 milliamps = 0.050 amps, as limited by the 40 watt, 120 volt light bulb.

In that figure it also appears that he used 120 ohms as a typical resistance for / “across” each of the sounders.

Since V= I x R, and inserting those values, V = 120 x 0.050 =

6 volts across each sounder. Yeah, Larry, it looks like you’re exactly right - one or two 6-volt lantern batteries ought to do just fine.

I infer that the rest of the 120 volts in the upper half (for simplicity - it’s essentially symmetrical) depicted circuit is lost across:

  • 6 volts across another similar sounder;

  • 100 volts across the RL1 variable resistor (potentiometer ?) at 2,010 ohms;

  • 8 volts through the half of the 20 miles of No. 9 iron wire at 300 ohms = 150 ohms;

6 + 6 + 100 + 8 = 120 volts Checks !

Corrections, comments, etc. welcome as always !

-Paul North.