Constant buzzing when charging from solar

I use my EB3A to charge my laptop when on the road. I generally charge the unit via the 12V plug (cigarette lighter) in my van and recently purchased a 200W solar panel.

I am very familiar with the sound of the fan and the odd ramp up noises it produces when charging from 12v or from AC. In those cases, the fan spins up presumably when a temp threshold is reached and then spins down when the temp has been reduced. However, when connected to solar, a loud hum starts almost immediately and never goes away until solar is removed. Is this constant loud hum normal? Am I at risk of damaging the unit? The noise is not coming from the fan.

I think you are hearing the fan driver circuit making noise. This noise is typical of the model and usually starts out as an annoying electronic hum which diminishes somewhat once the fan get running faster.

I am familiar with the sound as you described. I head that when connected to AC power. What I’m hearing here is different. This is a loud buzz that starts right away and does not go away.

@travelingzebra Can you take a video so we can check the noise?