Boosting tranformer output voltage

[underworld]

I picked up a small Lionel transformer at a show this weekend. The maximum output is 17 volts.

I have some pre war Marklin that I would like to run, but it is 20 volts. The loco will run but fairly slow. The transformer does have a whistle button that boosts the voltage to a little over 20 while depressed. Any ideas???

 

underworld

[Bob Keller]

Buy a transformer that can provide the power you need.

[underworld]

That's the idea, but right now I've got this one.

 

underworld

[Bob Keller]

We've done a few articles on using multiple small set transformers as a power supply, but you seem to want someone to tell you to leave the whistle button depressed (or some other workaround) to get a higher output. Not a good idea.

[underworld]

I didn't think leaving the button depressed would be good (probably overload). I included that information because I thought that there might be some circuitry in the transformer that might help in the solution.

 

underworld 

[Bob Keller]

Well, changing the internal circuitry of a transformer isn't such a hot idea. I don't think that Underwriter's Lab would think it too keen, either. Check our indexes. I believe that John Grams did a story between 1988 and 1994 about using multiple black set transformers (uh, 1044s I think - the cheapies with the lever on top) to combine their power. That would probably be a safer way to do it at less of a cost than a larger power supply.

[underworld]

Using multiple transformers would be fine. What I was thinking of was adding a few volts at the output...not really thinking about internal surgery. I remeber there is a way to add a few volts via a rectifier or something (many years since electronics classes) but if two transformers will give the voltage, that works for me.

 

underworld

[lionelsoni]

All three things that have been mentioned are possible:

The voltage of two transformers in series will indeed be the sum of their individual voltages (or the difference if they are out of phase with each other).

If you rectify the output and put a large enough filter capacitor on it, you will get about a 40-percent higher voltage (24 volts); but it will be DC, not AC.  However, the train will probably not care about that.  Use a bridge rectifier to keep the ripple voltage as low as possible.  You will need about 3000 microfarads per ampere of track current.  Use a capacitor with a working-voltage rating of 25 or more.

Getting a constant 5-volt boost out of a transformer is not hard.  Just bypass the whistle control and rectifier and put the whistle winding permanently in series with the output terminal.  For a 1033, for example, use point (6) in the schematic

http://pictures.olsenstoy.com/searchcd31.htm?itm=640

as the output instead of the U terminal.  Unfortunately, the transformer will start out at about 10 volts instead of 5, which may be higher than you want for low-speed operation.  Or not.

[underworld]

Thanks for all of the info!!!! I thought it would be something simple......too many years since electronics class!

underworld