Ground Hum - Rhodes 73 mkI

[soul]

Hi all,

I need a little assistance getting rid of some annoying ground hum that all of a sudden appeared on my Rhodes 73 Stage mkI. 

I had my friend replace a couple of tines, and since then Ive had some issues, including a buzzing noise that I can't get rid of. When I touch any parts inside the piano the hum gets louder. 

I am assuming this is a ground issue.  I have checked/cleaned the little grey RCA connector from the output jack to the board using Tronic Clean.  No difference.  Looking for some other suggestions ideas for troubleshooting.

...Also what the heck is thing I found rolling around the bottom of the piano?

[pianotuner steveo]

That is the pedal pitman.

It goes between the pedal rod and the big aluminum damper bar. When you press the pedal, it pushes that piece up and that piece raises the bar. You will need to remove at least one side of the damper bar to drop it back in place, but be sure it has good felt on BOTH  ends first to reduce noise.

The ground wire that goes to this bar may be disconnected also

[AFeastOfFriends]

I believe that if touching any parts increases the hum, the ground is bleeding into the signal. I'd check the pickup wires and anything involved in the signal line from the pickups to the wire on the ouput on the rail.

[pianotuner steveo]

Yes, but a broken ground wire at the damper bar is a common cause....

[soul]

Thanks!  So, it looks like I need to take the whole thing apart to see whats going on with the aluminum damper bar, find out if the ground wire is attached.  Ive never taken it apart.  Is it a straightforward process?  Anything to be cautious of?

[AFeastOfFriends]

The ground wire goes from an area near the RCA connector to the top of the damper bar in the rear left of the piano. You should only have to take the top off to see it.

That is, if I'm thinking of the right wire or mine is stock.

[pianotuner steveo]

I believe we are talking about the same wire. On either side of the damper bar us a set screw and a metal pin that holds the bar and holds it so it can pivot. By loosening one screw enough to slide the pin in,you can carefully lift the bar up and access the spot in the middle where you need to drop the pitman back in. The pin through the middle helps guide it.

Check for the ground wire being loose,missing, or broken at this point.

[Ben Bove]

An easy test is to take a metal screwdriver, and bridge the harp frame with the sustain bar.

make sure the screwdriver is touching the gold metal frame for the harp at the back of the piano, and also touch the silver aluminum bar that's under the harp way in the back of the piano. 

Because the dowel was detached and loose inside, my initial feeling too is that the ground wire that goes from the harp to the sustain rail is missing.

[David Aubke]

Just a note: I've got four pianos and I think only one of them (1973) included the sustain rail grounding wire. Since I believe I am the first owner of my Fifty Four, I'll venture to say that it wasn't always included from the factory.

Whether it was original equipment or not, don't rip your hair out looking for it inside the cabinet.

[soul]

I think I got it fixed now!  Put the pitman back in place.  Only has felt on one side.  I don't have a ground wire connection there.  There is a spring that hooks on the sustain bar and to a rod beneath.  It was hard to tell but I think I got it, the hum has disappeared.  Thanks to all of you! 

BTW:  Does anyone wanna sell me that metal rod that connects the pedal to the sustain bar?  Mine broke right at the threads.  Ive been trying to find a way to fix it.  Looks like I'll had to take it to a machine shop/welder.  Prob cheaper to buy another.

[pianotuner steveo]

I hope you put the felt side up so it touches the aluminum bar.

I always add felt to the other side too.

[soul]

Can anyone show me a photo of what the ground wire looks like?  I dont think I have one.  I thought I had this solved, but the output is full of hum and low level. The only way I can hear the piano is to crank up the mixer and that makes the hum really loud.

[Sarahvisjes]

http://i.imgur.com/PfLezIq.jpg?1
http://i.imgur.com/AnPpelO.jpg?1

This is a 1975 Mark 1 73 Stage