[Boatanchors] Patterson Power Supply Help Needed

[WA5CAB at cs.com]

Group,

  Joe is NOT looking for and doesn't need an audio transformer.  The one in 
the radio is probably still good.  The field coil on the missing speaker 
has nothing to do with the output transformer.  It is an electromagnet that 
doubles as a filter choke.  Only one winding.  NOT a transformer.    What Joe 
asked was what would be a reasonable resistor value to substitute for the 
field coil in the DC supply so that with a permag speaker he could find out 
whether the receiver works or not.  Before going to the trouble to find a 
suitable voice coil speaker or a physically and electrically suitable filter 
choke with which to convert the receiver for a permag speaker.

Robert D.

In a message dated 09/07/2013 18:08:11 PM Central Daylight Time, 
ark at ar88.net writes: 
> On 9/7/2013 2:56 PM, Joe Connor wrote:
> >I just picked up a nice Patterson PR-10 receiver but there is no speaker. 
> Originally, it had an electrodynamic speaker and a field coil. "LOAD 
> RESISTANCE"The schematic is here:
> >
> >http://www.nostalgiaair.org/PagesByModel/091/M0013091.pdf
> >
> >I want to substitute a PM speaker because I don't have much choice. The 
> schematic lists the field coil at 1.5K ohms. My plan is to change the filter 
> caps and substitute a 3K/10W resistor for the field coil just to see if 
> the receiver works. Does the sound reasonable? The two original filter caps 
> are 8 mfd. Should I up the second one to 22 mfd for better filtering now 
> that there is no field coil or am I better off adding a second 3K/10W resistor 
> and a third 10 mfd filter cap?
> >
> >I've read about these types of substitutions but have never had to do 
> one.
> >
> >Thank you for your help.
> >
> >Joe Connor
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