What is it?

This board serves a single purpose: Once the switch connected to the switch input gets closed, current from the AC input to the AC output is limited through large power resistors (effectively 45 Ohm). After a delay of approximately 1sec (longer for 110V-AC), an onboard power relay engages and directly connects the AC input to the AC output.

An onboard LED lights up, once the relay, capable of a load current up to 5A at up to 250V-AC, is closed.

Why should you use it?

The PSU Slow Start was intended as an important addition to the power supply of a DIY audio amplifier or other transformer/rectifier powered applications. When turning on the toroidal transformer of such a power supply with very large buffer caps, a large inrush current flows through the transformer which can be harmful to the transformer as well as other circuit elements.

Using the PSU Slow Start allows to limit the maximum current and therefore protects the transformer and other circuit elements of the expensive transformer based power supply.

Additionally, the "turn-on thump"-noise of the speaker system disappears! :)

How do I connect it?

(check out the wiring diagram image in the product photos at the top)

But it's as easy as... - connecting a suitable switch (voltage & current rating according to application) to the switch input - connecting the AC mains socket or cable to the AC input - connecting the primary winding of your transformer to the Trafo output of the board

... and you're good to go!

How large is the board?

For the outer dimensions as well as hole sizing and spacing, check out the technical drawing up top in the product photo gallery!