"Sylvia Else" wrote in message
...
Arfa Daily wrote:
"Sylvia Else" wrote in message
...
The sustaining pedal on my Yamaha electronic piano is become rather
flaky. Sometimes it doesn't sustain when pressed.

So I disassembled the piano enough to get at the mechanism, (removed 12
screws, and 6 bolts), and was rather surprised to see that the business
end consists of a potentiometre.

I'm not really surprised that it's failing. In fact, the surprise is
that it's lasted so long. When a piano is played, the sustaining pedal
is in constant use. I can't help feeling potentiometres were never
designed with that kind of use in mind.

The design seems rather primitive.

Sylvia.

It's not unusual to find pots in such applications, and there are types
which are specifically designed to have very long mechanical lives. Using
a pot keeps the circuitry simple. As an alternative, many guitar effects
pedals use an optical arrangement instead, where a shaded or shaped
'shutter' mechanically connected to the pedal, passes between an LED and
a phototransistor or diode, the varying DC resistance of the device
caused as a result of this, serving as the equivalent of the varying
resistance of your pot.

The latter seems a beter solution. Take a typical piece of Piano music -
Beethoven's well known "Moonlight Sonata" - it involves about 60 pedal
cycles. Apart from wirewound (and horribly expensive) pots, the best I've
found claims 100,000 cycles. I'd get through that in a year and half,
easily.

Sylvia.

So how long has the original lasted ? If it seems to have done reasonable
service, would it not be best to just replace it with a genuine one from
Yamaha ? They are very experienced in the field of keyboard instruments, and
I would have thought that they knew what they were doing in terms of best
cost / performance ratios when choosing components for their designs. The
only alternative that I see, is to use one of the 'horribly expensive" types
to improve on the original specification. If you are that bothered about the
lifetime of the standard device fitted, and having to replace it
periodically, then I would have thought that the one-off additional cost was
worth it ?

Arfa