Silence is Golden - Part 3
Well with the majority of the shack now MUCH quieter, its time to re-visit the Watson W-30AM. As some of you know this is a noisy supply in stock trim, the fan uses a current sense circuit to start the fan when under load - there are two problems with this. First the fan is supplied from the pre-regulator voltage of 22v (ouch) and also when using less than 3A (like when your radio is in RX) the supply never runs the fan; vausing the supply to become heat soaked after a few hours (read - damn hot!!).
I have tried a number of fixes for this issue, the winning combination appears to be;
1x 12v Regulator to provide a stable 12v for the fan 1x 22uF capacitor for smothing the output of the regulator 1x Arctic F8 TC Fan (thermo controlled fan) 1x 35 degree C thermal swtich (normally open)
So, at under 35 degrees, the fan is OFF, after 35 degrees the fan will adjust its speed based on the tempterature of the heat sync, and over 38 degrees the fan will run at full speed.
Once the fan gets the heat sync back down to about 28 degrees the fan will go back off.
Now the case stays cool, the heat sync (with the regulators and the rectifiers on it) stays at a reasonable temperature!! The only issue now is killing the mains hum!