In the days when I played Cordovox I would sometimes leave the amp/tone generator in the car, especially on multi-gig weekends ... Often, when I turned the unit on, I would get this sound like someone leaning on a bunch of keys at once ... the hairdryer became standard equipment ...
Now, I NEVER leave the gear in the car/truck overnight...

UD ... Wouldn't the blanket provide some kind of insulation from the cold? ... I don't know,, just asking...
t.