[AMRadio] Step Start

Jack Schmidling jack at schmidling.com
Mon Dec 11 12:20:21 EST 2006

I just ordered a trans for my pwsup and need to work around the hi/low 
step start designed into it.  It uses the 220 line to provide 110 or 220 
to the transformer.  The new one is 110 so I do not have this option.

I plan to reroute the hi/low switch to a resistor or better yet a light 
bulb to reduce in input voltage at start up.

The original was limited to 110v but with a resistor, I can provide any 
start up voltage I want so I need some help figuring out what resistance 
would be best.

There is a time delay relay that precludes putting any voltage on the 
primary for one minute to allow the tubes to warm up so I presume the 
hi/lo is to reduce the surge upon charging up the caps.

This is a choke input with two 4 mf in parallel across the output and 
somewhere it seemed to imply that the step start was only needed for cap 

As far as I can get with the heavy math, it seems like the resistor 
required would only be a few watts as it is only dealing with the 100k 
bleeder as a load.

Thoughts please.


PHOTO OF THE WEEK: http://schmidling.com/pow.htm
Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com

More information about the AMRadio mailing list

This page last updated 17 Dec 2017.