[Boatanchors] Patterson Power Supply Help Needed

[Al Klase]

Hi Joe,

Start with the '59 tube datasheet: 
http://www.mif.pg.gda.pl/homepages/frank/sheets/021/5/59.pdf

Working from the Class A1 power amp pentode column:

1)  Plate should be about 250 volts
2)  The screen grid should show 250 V or less.
3)  "LOAD RESISTANCE"  - You'll need an out put transformer with a 
primary impedance of about 6000 ohms
         Primary goes "horizontally" between the top two speaker 
terminals on the schematic.
4)  "SELF BIAS RESISTOR" - 410 ohms.  Schematics shows a 500 cathode 
resistor, that's OK
5)   "Grid #1 Voltage" -  -18 volts:  Adjust your substitute for the 
field coil to get +18 volts on the cathode resistor, assuming about 250 
volts on the plate.
         Feeld goes "vertically" between the right-hand two terminals.

I'd look around for a real output transformer if possible.  The PA 
line-to-voice-coil transformers were not designed for DC in the 
windings, but they're better than nothing.

I'd use a resistor for the field, and increase the second filter cap to 
47uF or more.

A choke, and caps near the specified values,  is the other alternative. 
Most (10 henry'ish) filter chokes are going to only be a couple hundred 
ohms, you could use one of these plus some resistance, and not worry 
about the caps.

In any event, keep the first filter cap near 8 uF.  Making it too big 
will increase the system voltage, and put extra stress on the power 
transformer.

Good luck,
Al - N3FRQ


.
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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