# Powering a LGB 51750 ?



## cape cod Todd (Jan 3, 2008)

Hello All
I recently acquired a LGB 51750 to power my electric switch machines. The unit came with directions but what I cannot decipher through the English and German wording and diagrams is how to connect power to this thing. I understand which connections to make for my paticular switch machines but not the transformer. I am using a LGB transformer 50171 that leads to a smaller handheld unit LGB 51750. The transformer pushes 20 volts out of it. Should the switch machine be connected to 20 volts? Seems high but the alternative is to connect it to the ohter side of the handheld that puts out a variable volt to the track. That doesn't make sense. 
On the switch box there is 2 male connectors and on the other side 2 female. I understand these are used to connect a booster and other units inline. Since I am only using the one unit should I make up plugs to connect onto the male ends and will that power the unit? 
The other choice and I think this is the correct one is to put power to the last 2 screw connectors on the 51750 unit. These are marked with a wiggly line and numbers 3 and 4 and also 17 and 18 on the screw terminal line. 
I am assuming that the black and white wire from the transformer will screw into these terminals but I would like to be sure before I fry the diodes or my switches. I would need to split the power from the transformer 2 wires to the handheld and 2 to the switch unit. 
If anyone can direct me to a good diagram or confirm my thoughts THANKS
Todd


----------



## krs (Feb 29, 2008)

I don't quite understand the problem. 
Do you have the user manual? 
If not you can download it from the Large Scale database: 
http://www.gbdb.info/details.php?image_id=2453 

The manual includes a circuit diagram of the 51750 and the information on the input power is this: 

_Electrical: The 51750 requires AC power from an LGB power supply. Power can be connected to the terminals numbered "3" and "4" on the screw terminal strip (Fig. 2) on the rear of the 51750. The green power indicator lamp lights when power is connected to the 51750. 
Use the male and female "piggyback" terminals on the sides of the box (Fig. 3) to connect several LGB con- trol boxes (e.g., 51750, 51800)._ 

20 volts AC on the input is fine. The AC gets half-wave rectified in the 51750 so one applies either a positive or negative voltage to the switch machine depending which direction you need to throw it.


----------



## cape cod Todd (Jan 3, 2008)

I believe you have confirmed what I thought KRS. I do have the directions that came with the switch box but they don't really tell where to pick up the juice to power the 51750. The #3 and 4 are colour coded black and white just like the connectors on the transformer so I will add wires to that to power the 51750. I figured that there would be something inside to handle the 20 volts but just wanted to make sure. I won't be using the piggyback terminals. 
Thanks for the info and handy link.


----------



## Dan Pierce (Jan 2, 2008)

Todd, the EPL drive has an orange and white dot. So does the 51750. Just hook up the colors for the EPL drives. 

Input power is 18 volts AC, and can be attached via a cable at the end of the unit, or terminals 3 and 4 (black and white). 

This unit was designed for the older 3 wire epl drives as well as the newer 2 wire drives. 

If adding a second unit, it just attaches to the first unit with the banana type connectors at the end. 

I prefer running the EPL booster as I get a much stronger/snappier pulse for the epl drives. 

So, my AC power goes directly to the booster and then the banana type connection has the 51750 attached without using any wires. 

Call me if you need more info.


----------



## cape cod Todd (Jan 3, 2008)

Thanks Dan and KRS for replying. 
It is all hooked up now and working well. I mounted the switch box and the throttle controller to a nice piece of wood ran 2 wires from the transformer to the terminals on the switchbox then used the male leads sticking out the side of the switch box to continue power to the throttle controller. My electric point throwers are the newer 2 wired ones so they were easy to hook up. A nice and tidy arrangement for my Christmas layout. 
Todd


----------



## magnetmb (3 mo ago)

Do not believe it's correct that you provide power directly to 3&4; that will not light the green indicator light on my 51750. Applying power to 17&18 will as indicated on the rear diagram. If you look at the rear diagram on the unit, it's pretty clearly indicating to connect the transformer to 17&18 and the instructions also show to connect those terminals to "Trafo" (German for transformer) with the circuit diagram symbol for AC. The references to 3&4 are to indicate that those terminals provide continuous AC power. For example, they show wiring a sephamore signal where the drive switch connects to switch terminals, and the light power source (needs to be constant) connects to 3&4. 3&4 pass through to the side terminals as well so you can connect other units. Just thought I'd share as I'm wiring mine and there seems to be incorrect info here.


----------



## Turbo4whl (5 mo ago)

magnetmb said:


> Do not believe it's correct that you provide power directly to 3&4; that will not light the green indicator light on my 51750. Applying power to 17&18 will as indicated on the rear diagram. If you look at the rear diagram on the unit, it's pretty clearly indicating to connect the transformer to 17&18 and the instructions also show to connect those terminals to "Trafo" (German for transformer) with the circuit diagram symbol for AC. The references to 3&4 are to indicate that those terminals provide continuous AC power. For example, they show wiring a sephamore signal where the drive switch connects to switch terminals, and the light power source (needs to be constant) connects to 3&4. 3&4 pass through to the side terminals as well so you can connect other units. Just thought I'd share as I'm wiring mine and there seems to be incorrect info here.



This post is 12 years old. The side of the switch box is labeled 3&4. They are common with 17&18 on the back of the switch box.


----------



## magnetmb (3 mo ago)

-deleted-


----------



## Turbo4whl (5 mo ago)

magnetmb said:


> Right. I know the post is old but it is easily found when searching for information about the 51750 so wanted to correct the record. My 51750 is , almost 30 years old and it's still relevant... lol.


Okay, I didn't say it but I will. Dan Pierce is correct. You are incorrect. Transformer 20V AC power should hook to the side pins 3&4. Yes you can hook power to 17&18 because they are common connections. Look at the diagram, 17&18 are feeding the track accessories with unswitched power.


----------



## magnetmb (3 mo ago)

-deleted-


----------



## Greg Elmassian (Jan 3, 2008)

SIDE PINS #3 & 4 - correct post #9
REAR PINS #3 & 4 - incorrect posts

Careful reading before you respond will avoid errors.


----------



## magnetmb (3 mo ago)

I edited my posts, feel free to remove. I guess it's LGB itself in the manual that seems to indicate the rear switch panel 3&4 should also work but doesn't seem to. That's what created the confusion. "Electrical: The 51750 requires AC power from an LGB power supply. *Power can be connected to the terminals numbered "3" and "4" on the screw terminal strip (Fig. 2) on the rear of the 51750.* The green power indicator lamp lights when power is connected to the 51750."

It's just a poorly written manual describing the connection. They should make clear that they are not referring to the actual terminal labels on the rear panel, but the sticker referring to 3&4 side pins for terminal labels 17&18.


----------



## Greg Elmassian (Jan 3, 2008)

Yes, looks like "side" got translated to "rear"... 

If you read German I'll bet it was ok. i have a Zimo system, and the translations make me want to pull my hair out.


----------

