[Boatanchors] Chokes & audio XFMRs

[hwhall at compuserve.com]

Drew wrote:
>
An audio or power transformer used as a choke would, as pointed out, have  
trouble with low inductance due to core saturation.  A transformer could be  
modified to saturate at higher DC current by disassembling the core laminations  
and reassembling so that all of the E's are in one stack and all of the I's are  
in another.  When reassembling the core into the winding, space the E stack away  
from the I stack with a piece of paper to provide an air gap. Less gap gives  
higher inductance and lower core saturation current; More gap gives lower  
inductance and higher core saturation current. This would be easiest with a  
bobbin-wound transformer. 
>
 
Drew, since audio xfmrs normally are stacked with separate Es & Is 
(not interleaved), I've been wondering whether it wouldn't be possible to use
an audio xfmr core to construct a choke. I see some biggish 70-volt audio xfmrs
at the surplus store. I suspect the original windings to be insufficient henries
for a power supply but they look easy enough to take apart, rewind on the old
bobbin, and then tinker with the E-to-I spacing for final inductance vs saturation
current. Actually, some understanding of that could be gotten with the original
windings to assist with estimating the turns needed for the final choke design, yes?
Noodling around the internet didn't turn up anyone that had tried this, just a lot
of folks that played with winding audio xfmrs on old power supply cores.

Wayne
WB4OGM