# Hand held DC throttle?



## lincoln pin (Feb 24, 2009)

Hello Again, I posted a question about building a hand held DC throttle awhile back and got some great advice. http://www.mylargescale.com/Communi...fault.aspx
But now I have a slightly different question. Can I take an old HO transformer (say an MRC Tech series) strip out the innards, bypass the bridge rectifier, feed it 22 vdc from a power supply and cram the controls back into a small hand held case and run a single engine (bachmann shay or lgb DRGW #50) (no sound) with it? Will the 22vdc input blow it up? or worse hurt me or my engines? LOL Or should I just build a throttle with the previous data? 
Thanks,
Mike


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## Greg Elmassian (Jan 3, 2008)

Probably, and it's real easy to get the definitive answer: 

Try it, if it goes up in smoke the answer is no, hahahahahaha ! 

Very few things nowadays are made with a lot of extra margin, voltage, current, etc. If you have the old transformer try it, but look at the voltage ratings on the components first. 

I would not bother, build a new one or buy something substantial. 

Regards, Greg


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## krs (Feb 29, 2008)

I actually used an MRC Tech H0 throttle many years ago with small engines. 
Worked fine except that the maximum speed was limited because the DC output voltage was only around 14 voilts max. 

But I'm with Greg when it comes to feeding the throttle with 22 VDC. 
Don't do it unless you know exactly what you're doing - it's very likely that some of the existing MRC components are not rated to handle the higher voltage or current. 

Knut


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## TonyWalsham (Jan 2, 2008)

If the old transformer is using a 2N3055 power transistor, do not feed the system with 22vDC. Magic smoke *will* eventuate.


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## Del Tapparo (Jan 4, 2008)

If you can live with 20V max, take one of my "Simple Critter Controls" (20V max, 5A, $29), mount in a box with a DPDT switch for direction changing.


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## lincoln pin (Feb 24, 2009)

Thanks Guys, 
Just what I suspected. I have made lots of "magic smoke" while experimenting with electronics. Maybe that where I got my curly hair from?

Mike


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