PianoDisc hum

[Larry Fisher RPT]

A one year old system would be the current design PianoCD if I remember your post correctly.

Humming could be coming from the powered speaker.  It has a separate power switch (if it's a AV570 or PDS100).  Pull the plug for the speaker or turn it off and see if the hum goes away.

Check for ground braid as posted by another tech.

The torioid transformer in the black power supply (usually mounted on the rim) doesn't start humming until it starts working hard  ..........   loud volumn covers up the hum.

Audio jack plugged in the wrong socket or not plugged in enough.  

Audo jack damaged.

Audo cable damaged.  The only real way to check this is to replace it.  Some damage occurs internally and can't be seen visually or measured with an ohm meter.

In a rare instance, the plug used to power the entire system was the culprit.  It was on the same circuit as the heater in the motorhome and so everytime the heater would come on, the piano would hum.  The only real way to check this is to use a suitable extension cord (12 guage) and plug in the system to a different circuit in the house.

Is the piano's audio plugged into any household stereo systems?  There may be a ground differential between the two systems.

Is it 60 cycle hum?  (a sharp B flat as I recall) or is it a faint noise like a fax machine?

Lar

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