Attention!!!! A PSU has soft start circuit. Turning on you can hear some stronger hum for some second. Please do not turn it on with load! Wait 20-30 seconds after turning off to turn on again. Fast turning on-off-on may cause the fuse blowing. Please replace by only with 5x20mm, 2-2.5A, glass, slow (time-lag) fuse. Do not use fast fuse because the start current will bow it out.