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MMD > Archives > July 1997 > 1997.07.31 > 15Prev  Next


Suction Boxes & Motor Controls
By Craig Brougher

Thomas Henden started a thread that concerns me, also.  I am a little
concerned that no one sells a decent suction box and solid state control
unit.  50 years ago the late Welte Mignon designs and I think some
Kimballs and a few others used an electric suction box that was almost
perfectly quiet.  I don't know who built these, but they were dandys,
stuffed in sawdust, if I recall!

Today, we put these "Screaming Mimi" blowers -- that turn probably 15,000
rpm and made from vibrating thin aluminum and these cheaply built, insane
little motors with no chance of being balanced -- into boxes and try to
quiet them down with felt.  Ridiculous.

I am going to put the blame for this squarely where it belongs -- on
the head of the lowly housewife who never makes a peep about her vacuum
cleaner that her neighbors can still hear ten flats away.  Vacuum
cleaners are like the Trouble Light -- they never worked that well when
they were new, so they decided to keep building them that way.  (There
are no Housewife Lobbies, so I'm safe).

 [ The cleaner salesman said to me, "Just *listen* to the power of the
 [ motor!" I replied, "Huh? I can't hear you!"   Then I think the same
 [ conversation happened again, but with a man selling a new nickelodeon!
 [ (They both seemed to be former used-car salesmen!)   -- Robbie

I discovered a fairly simple way to make the _old model_ PPC #650 suction
box work pretty well, however.  After rebuilding a pump player, they
would all be tight enough that the motor didn't have to turn fast, so you
could set it to 15% or so and it would just kinda growl silently and play
the piano moderately loud.

It was always the reroll in that case which gave me the problem.  I had
to turn the reroll knob all the way off to get it to do that slow, if I
recall now, so I never had quite enough poop left to get it started going
back.  What I did then was to modify the control by bringing out three
wires to the microswitch instead of two.  By adding another fixed
resistor in the circuit, I had separate control of reroll and play and
could set it where I wanted it.

Now we got a problem: The fellow responsible for this junk has changed
his circuits or components or both again -- this time the motor won't
even start to turn until you have the controller set to about 80% of top
end (a discontinued triac, I am told).  After it starts of course, you
can turn the motor down, but the controlling circuit is highly unstable
and weak, and will probably burn out without enough noise quenching in
the gate circuit.

Nobody at PPC knows anything at all about them anyway.  I strongly
suggest boxing them back up and returning the whole thing to PPC.  It's
the only thing they understand, for sure.  Then they just give them back
to (this fellow) and he makes it good to PPC.  I have tried to speak to
him about it, and he simply turned on his heel and walked off.  I doubt
that he really cares to make anything work 100% right.  Whatever stays
sold is a vote for him in his mind.

If someone would build a properly designed dual speed controller with a
low profile that will mount under a keybed and ask a reasonable price,
they will sell thousands of them, I'm sure about that! There is no trick
to it except keeping your costs low, the circuit simple, and the
appearance convenient and desirable.

Also, those Grainger motor control units are not ideal either, even
though they at least control the motor well! They are not designed to
hide or to operate without looking, and don't provide two separate
controls.  I would also suggest slide controls instead of rotary knobs on
opposite sides of the control box with the on/off switch planted in the
middle so you don't have to even look.

Somebody needs to do it right, once!

Craig Brougher


(Message sent Thu 31 Jul 1997, 12:19:57 GMT, from time zone GMT.)

Key Words in Subject:  Boxes, Controls, Motor, Suction

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