Purpose of the fibre shoulder washers

[Bourney]

Hi all,

Hoping someone can educate me on the purpose of the fibre shoulder washers used to mount the OT3s.

I can see they are insulating the screw from the chassis, but then we connect the OT3 and the screw to the main ground lug anyway.

Is the aim to achieve a single point of ground? Or are we trying to insulate from possible vibration from the transformer?

Thanks for any guidance you can share.

[Paul Joppa]

Yes, it's to provide a single point chassis (safety) ground. It kills one of the many possible causes of hum and/or radio interference.