The problems Phil Dayson reported about his Pedal-Electric Duo-Art (PEDA)
are both pretty typical.  I've put together a few ideas about ways to
improve things, gleaned from a number of UK Duo-Art experts as I
encountered the same problems.  I hope they are of use -- they helped me
when I needed it.

PEDAs often are sluggish to pedal.  I don't think it's down to the
reservoir design, as this is identical to the ordinary Pianola version.
Lack of accenting is most likely to be due to having reservoir springs
that are too weak -- possibly broken.  The effect is to give more
reservoir travel, hence more absorption of the foot accents.  If the
system had been modified at all for electric use, it would surely have
been to strengthen the springs, which would assist foot-pedalled accents.

There should be two steel V springs inside a Pianola / PEDA reservoir,
giving low-tension reserve which remains relatively constant as the
reservoir shuts, and keeps the wind motor going and notes playing.  There
should also be a stiff wooden spring outside, which provides a small
amount of high-tension reserve (which rises very rapidly as the reservoir
shuts) for accented playing.

The wooden spring should only cut in when reservoir is half-closed.
Owners of other players should note that this pairing of two types of
reserve, however achieved, is fundamental for effective foot-operated
playing.  You won't find it described in any service book!

If the wooden spring has broken, which can happen in electric
instruments, pedalling will be very difficult as you will get virtually
no stack tension until the reservoir completely shuts, then all of a
sudden you get no reserve at all.  If the V-springs break the wind motor
will shudder between foot strokes.

Another possible cause of sluggishness is a constriction in the wind
supply.  I have seen DAs where the supply cutoff slider in the expression
box hardly opens.  The high suction of an electric pump can drive the
system but the low suction from foot pedals won't.

A third possible cause of problems is the one-way valve between electric
pump and the rest of the system -- if this leaks, foot pedalling will be
difficult, and possibly the suction relief valve may be cutting in (on UK
PEDA uprights it is often a knife valve letting atmospheric air into the
motor line).

In any case, a PEDA should be just as easy to pedal as a Pianola (even if
a lot aren't).  Keep adjusting away until it goes! If all else fails,
bypass the expression box and connect the stack directly to the foot
pump, as that will at least prove the stack's easy to pedal.

The second problem, of accompaniment drop-out at low suction, is a well-
known design weakness peculiar to the PEDA.  The Duo-Art expression
accordion pneumatics pull down an intermediate lever which in turn moves
the shaft connected to the regulating knife valve.  Both the rotating
shaft and the intermediate lever have return springs to pull the system
back to zero level.

Setting the knife valve return springs strong enough is essential to get
quiet DA playing, because the return force must be enough to completely
close the knife valve to zero level against the friction caused by the
suction supply acting on a large flat surface.  The return spring for the
accordions only needs to be strong enough to move their own weight.

For any DA system, if the accordion intermediate lever lifts off the
rotating shaft when the expression level drops, then the knife valve is
not closing fully and the system will not play as quietly as required.
The return spring on the rotating shaft needs to be strengthened to
ensure it closes promptly under all circumstances -- this adjustment can
only be done effectively when the suction motor is working, as this
increases friction on the knife valve.  Watching a system when playing
makes this problem immediately apparent.

The stronger the knife valve return springs are made, the more force is
needed to close them.  This is the classic problem with PEDA adjustment,
as keeping the accordions shut at low suction supply levels may lead to
the electrically-powered DA failing to play quietly.  The compromise is
to slacken off accordion return springs until they are just strong
enough, and make sure the knife valve is as friction-free as possible,
which reduces the force needed to re-close it.  Well-balanced systems seem
to work OK.

I hope these points are of some use.  Other more experienced Duo-Art
rebuilders may be able to offer further tips.

Julian Dyer