11801 questions - funny fan noise and light

Ragnar S

Hi all,

I have some questions about a 11801;

- After it has been powered on for a while, 20 minutes or so, the fan starts to make interesting sounds, like if it is revving up one or a few times a second, only for a fraction of a second. Is this normal? Could it be a problem with the fan speed regulation, or maybe a mechanical problem with the fan itself?
Interestingly, if I remove the screws to the fan and just hold it in my hand it stops doing that, like if it had something to do with the resistance for the air it tries to move, or maybe a problem with how it is mounted. But I have not succeeded to make it do the sound by blocking the air path.

- There is a small neon (?) light in the power supply that can be seen through the fan or from the top when the lid is off, that flickers. Is it supposed to do that?

Thanks for any hints, and best regards,


Join TekScopes@groups.io to automatically receive all group messages.