Weird power-up behaviour of my Velleman amp kits...

[LBuzzer]

Hi all,
I'm doing initial power-up testing of my just-completed amp kits. The transformers I'm using (2 monoblocks) are the ones recommended in the kit brochures, and the wiring all matches up fine.

I'm also doing what the brochure suggests: putting in a light bulb in series with the power cord's HOT wire to see if I have shorts anywhere.

Both of my monoblocks do the same thing, which leads me to believe that it's normal but this is what happens: I flip the switch and the light bulb lights up only to fade off again after half a second. The bulb is not burnt out as I've done this a few times now. Nothing smokes or gets warm on the PCB. I've also doubled the power supply capacitance. Could this behaviour be caused by the caps charging up? Please note that I've already blown a 1A slo-blo fuse they recommend using in the amp kit brochure. Should I up-rate the fuse? I suppose, if it can't survive the charge-up phase....

No input signal connected, no speaker connected, either. Only the transformer to the bare, completed PCB. The kit # BTW is K8060.

Thanks muchachos!

[richie00boy]

LOL that's what is supposed to happen! The bulb only light up when a surge is happening, such as inrush current at turn on, or a fault with the amp.

[Jan Dupont]

It seems like your amps are ok...
The light bulp showing normal inrush current when charging caps, and since nothing gets hot, I think it should be ok.
Measure for DC at the output, and try connecting one of the amps to a speaker and a low level input signal (still with the light bulp in series with the main).