Akai AP-100c picking up motor hum

[Wee Beastie]

Hey, I just bought a used Akai AP-100c turntable in great condition except...the stylus seems to pick up the hum of the motor. It is not a ground wire issue, nor an RCA cable issue. There is no hum till the needle touches the record. The hum continues if you manually stop the turntable from spinning. It stays the same pitch if you switch from 33 to 45 RPM. I am certain that it is a loud motor (it is all relative...the motor isn't "loud", per se, but when transmitted through the stylus, it can be heard as a steady hum, not loud enough to get in the way of a busy track (and I didn't crank the sound when I tested it before buying guess I shoulda), but definitely loud enough to, say, ruin "Speak to Me" from Dark Side of the Moon.
How do I fix this?

 

[rhagen]

Hello! Did you solve this issue? I have the same on my Akai AP-001c

 

[kels83]

Following up for people with this table who experience this issue in the future. My symptoms were an audible him only on the left channel with the motor on, and a loud hum with the motor off and the headshell removed. I was able to isolate the problem by removing the bottom cover and hooking a wire with alligator pins as a temporary jumper-to-ground with one end clipped to the phono ground. With the TT on, I then hunted around with the other end of the temporary ground wire on the internal ground point, tonearm, and motor. I hope this is obvious, but DON'T TOUCH IT TO ANYTHING ON THE POWER BOARD OR MOTOR WIRES containing live current. Touching my ground wire to the motor BODY eliminated my hum.

I noticed the motor body had one screw with a clean, unused solder lug. I soldered a permanent jumper from that lug over to the center contact point on the audio board. I soldered the other end to the contact point where the external ground wire comes into from the back. There are 5 little raised pins ordered R+, RG, 2 tiny grounds that run into the tonearm, LG, L+. I soldered to the middle contact with the 2 tiny ground wires, adding a third that jumps the motor ground over to the phono ground. It took about 6-7 inches of wire.

If you don't have a solder lug, you could easily clean the finish to bare metal and solder directly to the body, or you could remove a screw and add a metal washer or a crimp terminal under the screw to connect to.

I realize the motor ground is AC and the phono ground is DC. But after researching, I don't believe the earth cares what type of current it returns to its home. This completely eliminated my hum with a headshell plugged in even at high volumes. It also reduced my hum with the headshell removed by 95% (was loud previously) to basically inaudible unless the amp is turned way up. I've played records on it for several hours now and it works perfectly. The motor also seems to run cooler when I touch it than before. Preamp is also nice and cool. I'll report back if I have any issues with it.

Best of luck!