Author Topic: Hum from new MkII  (Read 921 times)

Offline jbowers

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Hum from new MkII
« on: April 01, 2010, 08:36:14 AM »
Hey all,

Brand new rhodes owner. Just picked up a Mk2 stage piano in pretty good nick. I've just finished voicing it and its sounding great. However there is a hum which seems like it just appeared while I was working on it. It is remedied by putting my finger on the jack, as well as on various parts of the harp. Any idea on what this might be and how I can fix it.

Also, in the upper register the two notes either side of the 'split' where the brace goes seem to buzz a little. Any ideas on how to stop that?

Cheers,
James

Offline Steve in CA

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Hum from new MkII
« Reply #1 on: August 04, 2010, 02:12:15 PM »
James -

A "hum" which goes away when touched is indicative of a bad ground somewhere between your amplifier and the pickups in the keyboard.

(could even be your patch cord !)

Anyway - the Mk 1's I worked would pick up some corrosion and it hampered good electrical contact at the phono connector which was located at the left side of the instrument.  A grey molded RCA plug connected to the jack and a shielded cable carried signal to the volume control and tone control and finally the output jack - - THis jack and plug combination was a problem in some older instruments.

Examine all - look for signs of corrosion - wiggle (gently) wiring and any components.  

The "buzzing" you describe at the "split" is a common problem resulting from the tone bars of the associated keys on either side of the brace, ever so slightly touching the brace itself - - they then "vibrate" against the brace.  Try just grasping the tonebar of each (one at  a time) and twisting the assembly - ever so slightly - away from the brace.  This will confirm the problem - the next problem is to prvent the tonebars from coming back in contact with the brace if they do so . . . . play each note several times with vigor to see iff they drift back in contact.

Good luck

Offline Ben Bove

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Hum from new MkII
« Reply #2 on: August 05, 2010, 02:10:50 AM »
Steves right on about the ground, especially in a stage only model.

With the buzzing on the high notes, bending the brace is a quick fix. Feel free to forcefully pull on the metal brace that goes between the tonebars, pulling left or right in the middle of the brace until buzzing stops. If you can wiggle your tonebars left and right though a good distance, then Its probably best to replace the grommets, the black rubber things between the screws and the tonebars. They help hold the tonebars in place.
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