DIY 300B and PX25 (in a single chassis)

Chassis: 鈴蘭堂 SL-990
Rectifier Tube: U18 / 274A
Driver Tube: WE437a
Power Tube: WE300B / PX25
Power Transformer: Tango CT-250
Inter-stage Transformer:Tango NC-15
Output Transformer: Tango X2.7

Yamamoto socket fits for either WE300B or PX25

WE437A self bias by using 120ohm resistor

Selector for WE300B or PX25

Selectors' Inside - Cathode resistors with heat sink

Back

Front

My 300B / PX25 project was completed in June 2013

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Because power supply for WE437A is built by using a resistor to reduce the voltage from 450VDC to 200VDC, the voltage will be very high in the beginning.  In mid 2014, I added a timer that lets the WE437A have a soft start power supply.

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Rare WE437A with square-getter and tip top