Ranger Filter Capacitors - RT's Radio Home Page
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Ranger Filter Capacitors
Amateur Radio > E.F. Johnson Restoration
High Voltage Supply (600 VDC)
Viking Rangers seem to have a little more hum than other Johnson gear. The HV power supply filter capacitor is 10uf @700 VDC. I believe this was a compromise due to the expense of that component in the 1950's. The filter value can be brought up with currently available capacitors in series. **Resist the urge to go signiciantly higher in capacitance; the resulting B+ voltage will exceed the ratings of other components. I tried using a pair of 100uf @ 450 VDC capacitors (50uf result); the result was B+ was so high, R15, a 30K, 20 watt resistor overheated and failed. A pair of 33uf @450 VDC capacitors in series (16.5uF Result) works well in my Rangers.
Low Voltage Supply (300 VDC)
The factory installed a 30uF @450VDC. I use a 47uF @ 450VDC.
Late Ranger I with keyer platform:
The pair of 15uf @150VDC (C90A and C90B) can be replaced with a single axial 33 uF to 47uF.