[AMRadio] Step Start

John E. Coleman (ARS WA5BXO) wa5bxo2006 at pctechref.com
Mon Dec 11 13:18:21 EST 2006

Jack I would dispense with the startup circuit.  With the choke input filter
system and only 4mf of output capacitance you want need a start up circuit.
When I hit the push to talk switch is when my PS plate XFMR comes on.  The
heaters to the 866 are on all the time.


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Jack Schmidling
Sent: Monday, December 11, 2006 11:20 AM
To: Discussion of AM Radio in the Amateur Service
Subject: [AMRadio] Step Start

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.


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