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Hum from Empire 698

Hi guys.

I'm having a hum problem with a 698 that was given to me. The motor is not completely quiet either.

When it was given to me the headshell was broken so I replaced it with a standard removable type. This required trimming the length of the arm about a .5 inch and rewiring the arm. The internal wire was replaced with van den Hul. The arm works great and is quiet on it's own. I did have to add a ground wire from the chassis to the tonearm ground to stop a loud hum from occurring.

When playing a record there is a constant hum until the arm is returned to the armrest. As long as the arm is in the rest it is quiet. As soon as the arm is raised from the rest there is a hum. There is also some noise from the motor but it can't be heard from a couple of feet away.

I took the circuit board out and looked at the caps and it appears the power switch capacitor has been changed to a Sprague .2uf 600v.

Any ideas?
rwwear

Showing 1 response by normansizemore

normansizemore
601 posts
 
rwwear,

Sounds like the cartridge is picking up a open ground loop from the motor.  
When the stylus is moved over the platter (i.e. in closer proximity to the motor) your getting hum. 60hz I would imagine.  Try placing an additional rubber matt on the platter and see if the hum is reduced or disappears.  I am flying blind here, but I would think that your issue is in the motor, since you properly rewired the arm.

If the hum experiment above is sucessful, then a motor rebuild or replacement is in order. Being that it's making noise (is should be dead quiet), that is where I would look. 

Good luck, the 698 is a wonderful table and worth the effort to sort matters out.
Norman
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