x

motor grounding issues

jamesshipp 11 April 2014

Hi All-

I am having some grounding issues on both of my vibraphone motors since I had some work done on them, wondering if anyone can suggest remedies that don't involve returning to the busy shop that did the work for me in the first place?

Went to record myself the other day, and I'm getting a buzz on the recording whenever I turn on the motor. With this, my 'house' vibraphone, I would assume this is due to the grounding post in the plug for the motor having fallen off at some point in the last 18 years I've owned it. But I have the same buzz issue with my younger vibraphone (which HAS a grounding post) on certain gigs in the house system, especially if anyone in the band is using internal guitar mics or active pickups.

I had both motors altered a few years ago so that their speed is expression pedal-controlled instead of the knob, and I assume the issue is new since then. Is there anything I can get to act as a buffer between my motor's plug and the wall socket or power strip it's going into that will ground it so this buzz isn't an issue, or is this something that has to be corrected in the control box itself?

thanks-

JAmes

Comments

IndianaGlen Fri, 04/11/2014 - 19:41

I have a bunch of questions and a few comments.

First where is the sound coming from? Is it coming The body of the motor or is it introducing electrical noise (EMF)? If you push the motor from side to side does the sound change or go away? Does the pitch change with when you change the speed of the motor?

Which motors are they? Are they the newer small motors that are in the M-55 (Oriental Motor)? First of all eliminate anything mechanical. I am assuming that the motor itself is buzzing, and not causing electrical hum on a mic etc. Another quick test is to loosen the mounting bolts/screws until the motor is almost sloppy in the frame and see if the sound goes away, if it does, then perhaps replacing additional rubber on the mounts etc may help.

I am not a sound guy, however I know that ground loops can drive sound guys crazy. You may have an electrical problem that makes the mechanical problem worse. Maybe a sound guy can add some info regarding an isolation transformer/power strip.

It is possible to introduce electrical noise (EMF) if you have longer runs of wire (e.g.) adding an expression pedal. They do make electrical shielding that's kind of like tape. It may be possible to safely shield the wires and ground the running to the pedal, but I'd do that as a last resort.

I may be able to talk you through shielding and grounding but first it will be helpful to know which motor you have.

If you have a missing ground plug fix it. The main purpose for the ground is to keep you from getting zapped if something goes wrong with your equipment.

--IG

jamesshipp Sun, 04/20/2014 - 14:27

Hi Glen- thanks so much for your advice. I have a 20-year-old motor/control box on one vibraphone and a 5-year-old one on the new vibraphone, and they are both apparently capable of causing this problem, which is not acoustic or mechanical in nature; it is through the electrical system I am plugging it into that it is somehow causing buzzing on PAs and recording converters when using microphones. The buzz is only there when the motor is running, not just when the power switch is turned on. This had never happened with either instrument until I had the modification done.

Current plan is to take one of the motors back to the guy who did the work for me, and see if he can figure out what's going on.

thanks all-

JAmes

Steve Shapiro Sat, 04/12/2014 - 22:34

James,
Probably a ground loop. Make sure you plug everything into the same outlet. But do yourself a favor and fix that plug! The ground is important, and I've gotten some weird shocks from those old motors. All you need is a $2 replacement from a hardware store with some screw terminals.
SS

Forums

x
⇡