ODS Eyelet Boards

[martin manning]

SSS Bipolar supply board has been updated to include a current limiting resistor at the bias tap input, and a resistor across the positive output.

The 33 ohm AC input resistor reduces the peak charging current pulses by about half, and reduces the RMS current drawn from the PT by about 30%. As far as I know, no one has lost a transformer using this driver supply circuit, but it seems worth the effort to add this feature, and it may help reduce noise. The output voltage drops a few volts on each side, but there is still more than enough for the circuit to operate. The complete adjustable bias supply network is also shown, with values adjusted to recover the original design bias voltage, and reduce the current draw slightly.

The 330k resistor across the positive side partially balances the current draw from the bias circuit, and also acts as a bleeder. It could be located anywhere, but it"s convenient to place it across the output eyelets on this board.