Rotex RO125 Making Grinding Noises - (Video Attached)

[TheSergeant]

I recently picked up a used RO125 that has literally went through 9 pieces of paper and is in basically in mint condition.  I'm noticing some pretty loud grinding sounds coming from sander when it's running in either random orbit or rotex mode.  It's noticeable at slow speeds as well as high and when sanding and when holding the sander in the air. 

Is this normal or does this need to be serviced? Does a bearing need replacing?  I'm very comfortable working on tools so if this is something that can be fixed I'm all ears. 

Thanks guys!

 

[Rick Christopherson]

Nope, that's the normal sound. It's coming from the PWM speed control, and that is why you hear it more pronounced at the lower speed.

 

[AlexThePalex]

It's just the normal sound, due to the gears and mechanism of the Rotex. Don't see what the PWM speed control has to do with it as the noise persists at any speed, just higher pitched at a higher speed which is also normal. At higher speed the noise of the motor itself is also louder so that's why the grinding noise stands out more at lower speeds.

The Rotex certainly is something to get used to, and the noise not the least.

 

[Rick Christopherson]

Don't see what the PWM speed control has to do with it as the noise persists at any speed.....

________________________________ But it is due to the PWM control, just as it is with the track saws. It is the pulsed motor output interacting with the drivetrain.

 

[TheSergeant]

Thanks for the quick response guys!  You put my concerns at rest.  My ATF55 has the same groan to it but I guess I didn't realize that the Rotex had a speed controller.    Good to know.  Thanks again!

 

[ear3]

Yeah, totally normal, as people have already said.

This a good reminder for me of a game/test I've thought about setting up and posting to the FOG, but have never had the time to do.  Basically: Name that tool noise.  Can post it to one of those survey sites with multiple choice answers and see how many people can get.