TENTLABS-VANDERVEEN E-CHOKE Protection
We encountered some broken E-chokes in the past. The transfer of high voltage worked fine, but the hum reduction had gone. We have analyzed the problem and solved it.
Figure 1 show the application of the E-choke. The high voltage is rectified and buffered in the internal capacitor C1 = 330 uF/450V. At the output of the E-choke is the second buffer capacitor C2 of the actual power amplifier. In my UL40-S2 this C2 also equals 330uF/450V.
What happens when we switch on the mains? C1 is very quickly charged through de diodes D1-4. The capacitor C2 is charged through the E-choke. With an extra diode we control the charging current to C2. Now the E-choke stays in its safe operating area.
The new diode (1N4007) must be soldered at the bottom side of the PCB, just below the time-selector jumper, parallel to the 1M resistor, with its cathode (white ring) facing to ground. See the photo for more information.
Starting 2011 we delivered our E-chokes with this extra diode. Earlier E-chokes don't have it. We advise you to place it to protect your E-choke.