Power Supply Considerations

[Richard Post]

Anyone try a choke input, possibly in the negative line?  The doubler 
nature of the HP-23 hi-volt complicates this a bit.  Anyone have 
access to modeling software?

Rich


At 8:49 AM -0400 4/11/08, Alan W. Fremmer wrote:
>Fellow Restorers/Collectors:
>
>I'm in need of your expertise once again.  I have a Harvey-Wells T-90  in
>need of a power supply.  I decided to try and use what's available,  namely a
>Heathkit HP-23B.  The T-90 requires HV B+ of 500-600 volts and LV  B+ of 300
>volts.  The power supply provides 820 volts, no load and 700  volts 
>at 250 ma.  It
>also provides the low voltage B+.
>
>Using a back of the envelope Ohm's Law calculation (I don't recall  what
>parameters I chose) I came up with the idea of putting approximately 
>a 500  ohm,
>25 watt resistor in series with the HV line.  The closest value I  had at hand
>was 750 ohms.  Well, everything seems to be working but I need  your
>assurance.  Here are my measurements: IR drop across resistor, 127 
>volts, plate
>current at resonance about 100 ma, total current through the 
>resistor, 167 ma,
>watts out 60.  The resistor gets VERY hot.  I'm  calculating 20 
>watts dissipation.
>
>Would very much appreciate any suggestions as to how to improve or modify 
>the setup, including getting a power supply with the voltages closer to those 
>actually needed.
>
>Thanks in advance for your past help and for whatever you can tell me about 
>the present circumstance.
>
>73, Alan - KB2HEI

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