Watson W-30AM Power Supply

I've had this great linear power supply for a number of years now and it has served me well. Since getting higher powered rigs I've come to the conclusion that the fan noise is now unacceptable.

Supplying 10 Amps to the FT-450D whilst it was
transmitting 35 watts.

The Watson W-30AM is a bench power supply supplying 30 amps continuous (35 amps peak) at 13.8 Volts.

It has a number of outputs

• Terminal binding posts giving up to 35Amps
• A cigarette lighter socket supplying 10 Amps
• 2 pairs of spring terminal sockets supplying 6 Amps

The full specification is this:

• Output Voltage 0 - 15V DC 
• Output Current 30A (35A Peak) 
• Over current protected 
• Dual Meters 
• 3 sets of terminals 
• Cigar socket 
• Rubber feet 
• Front Panel Fuse 
• Supply 230V AC 50Hz 
• Size 240 x 150 x 230mm 
• Weight 8.6kg 

Built to a very similar specification as the W-25AM, the W-30AM offers an increased power capability providing a full 30A output at 50% duty cycle and up to 35A peak current. An efficient internal transformer keeps the case size exactly the same as the W-25AM. As such it is able to power a very wide range of electronic items including most radio transmitters and transceivers. Professionals will appreciate the extra margin of power output available, and ham radio operators will find it able to cope with heavy duty cycle transmissions demanded by FM.

The adjustable voltage has a detent at 13.8 volts. It also has large analog meters for volts and amps.
In the UK the mains fuse is 4 Amps.

I saw it still on sale in the UK for £122.56 from radioworld.co.uk recently (September 2015) so it is still in production.

The cabinet is steel and recently has been developing a loud resonant buzz when you initially switch it on from cold. After a few minutes that disappears.

Operation

In operation I find that a rig taking less than 3 amps (all of my older rigs) will not trigger the auto sensing cooling fan into operation. Sadly all my new rigs trigger the fan. I have had to put the power supply under the desk but still that does not quieten it enough.

There is a modification circulating on the internet for a similar power supply the Watson W-25AM, where people have lowered the voltage being fed to the fan with a 27 ohm 1 watt resistor. There is also talk of replacing the fan with an 80mm fan from a PC.

Future

I have bought a switched mode power supply (Moonraker badged PS30SWII 30 Amp power supply) for the HF rig which has a noise tuner built in. Essentially a knob that moves birdies (if they are present) out of the current band you are operating on. This power supply appears to be exactly the same as the QJE Dx PS30SW II power supplies which gets great reviews on eHam.net.

A lot of people don't like switched mode power supplies because of the RF noise that sometimes are generated. I might make the voltage lowering mod to the Watson if the Moonraker one does generate RFI - watch this space.