Effects of sagging mains voltage on amplifier current draw

[ncgrove]

So the other day I played an outdoor show where the whole setup... my bass rig, guitar amps, PA, sound board, and lights were being run off one generator. Suffice it to say there were oodles of power strips and extension cords. Certainly not optimal.

About halfway through the show, the power amp in my bass rig (an old Carver PM-350) decided it had enough and shut down. Luckily I was plugged in direct to the PA, so there wasn't a huge catastrophe. My pre-amp and compressor survived unscathed. Turns out the Carver just popped the fuse. I threw a new fuse in when I got home, and it works just fine.

My suspicion is that with all of the crap being run off of one generator, there was a voltage sag occurring. I have the idea that as the AC voltage drops, the power supply in the amp draws (or tries to draw) more current to maintain constant power to the rest of the amplifier. And this increased current draw kills fuses.

I've tried to find some good information on the internet about sagging mains voltage and power supplies, but it looks like there are a lot of misconceptions (probably including mine) about how all this works. And since I come here for no bologna information, I'll ask yall to either set me straight, or tell me I'm on to something.

[Bill Fitzmaurice]

When voltage goes down current goes up. Fuses are current limiting devices so yes, low voltage will pop fuses. It also creates a lot of heat along with that current, which can damage gear. That's the purpose of the fuse. When doing a generator gig specify the size required, and don't accept no for an answer. Walk if you have to. No gig is worth ruining your gear.

[Israel]

we at least double the power needed when on generator and specify the gen is only for music gear (if not youll see peeps plugging in fridges and inflables, etc) even we specify how loud the gen should sound