Mike Knudsen wrote in 010730 MMDigest:

> I'm the character who bought the Dynavoice keytop piano player at
> the Wabash rally mart.  A week later I got home and tried it out.
> It's not in bad shape: everything works except about six notes are
> stuck on due to the nipples having broken off on the valve blocks.
> I've read through all the MMD Archive articles on the Dynavoice, and
> this seems to be expected.  Also the playing is weak and not snappy.
>
> Mine is a Model PL51, serial #2150, with the transposing tracker
> bar, valves in the roll tracking system (which looked like a 4-hole
> Simplex but uses only one hole per side), and a triac circuit for
> continuous control of the turbine motor.

You are extremely fortunate to find the PL51 with the transposing
tracker bar!  This unit also has the plastic pneumatic units which
are the easier ones to disassemble, (easier than the later models
which used a different glue that's murder!).

> The "Volume" knob is marked for three loudness levels, but the
> knob rotates quite a ways on either side of those.  Might the triac
> motor speed circuit be a retrofit?

The triac is original.  Three loudness levels on dial are relative.
Prior (1st) model did have three fixed speeds.  This model (2nd) is
variable speed; a definite improvement..

On the underside of the volume control is an additional trimmer to set
the overall range.

Be careful with exposed wire connections; the whole works is at 110
volts.  Marking the power cord for polarity and installing a master
switch on the power line input socket is highly recommended for
convenience and safety, especially while working on the unit with the
covers off.

> The roll drive is impressive and solidly built: separate motors
> for play and rewind, with the pinball machine type of
> self-disengaging armature on the play motor.

Oil everything!  Motor bearings and gear housing all have access holes.
Oil the take-up roll shaft ends, the roll holders.  Lubricate the
slider thingy on the right spool holder ( part of the centering
system).  At such time you remove the vacuum motor, take the motor
apart and soak the two bearings with 30 wt oil.

> There's one extreme treble pneumatic unit with no striker or
> tracker bar tube, just open to the air, with a micro-switch.  It
> seems to be intended to throw the switch when vacuum is attained.
> Maybe it shorts out the speed-control triac when the unit is first
> getting up to speed, and also if a big chord kills the vacuum.

This is a safety switch that interrupts the rewind circuit, until the
vacuum drops off the nil.

Re rewind:  Any roll that isn't absolutely perfect will trigger the
auto rewind system.  Also, until you upgrade the Dynavoice's tracking
system, you will find it tends to wander a great deal, which will
trigger the rewind.  The rewind port on the tracker bar should be taped
over or otherwise disengaged at the pneumatic on the left of the roll
frame.  Trigger the rewind manually.  Believe me, it will make you a
lot happier in the end!

> Also I have to remove the fallboard key cover to get the unit
> far back enough on the keys.  Maybe Duo-Art keys aren't quite full
> length front to back; this has been discussed lately regarding
> Steinways.

The unit perches on the front of the key-bed.  I does not push back all
the way to the fallboard as you would think.  Notice two clip thingys
at each end.  Push them back and they then fall down in front of the
white key faces at each end, with a tang that drops between the key face
and the front cover board.  This positions the Dynavoice correctly on
the keyboard and sort-of locks it in place.  The front row of strikers
will be right out on the very end of the white keys.

> The foam filter blocks above each valve outlet are turning to
> dust and will have to be removed before they clog the workings.
> All pouches, valves, and pneumatics seem to be still flexible and
> working.

Use a powerful tank vacuum with a crevice tool.  Place the vacuum as
close to the foam filter blocks as possible while teasing the block
with a dental pick or whatever.  The foam will disappear at the speed
of light.

> How can I repair the broken nipples?  Their inside diameter is so
> narrow that even if I could find brass tubing thin enough to stick
> in the hole, the inside diameter would be reduced to less than a
> tracker bar opening, which would stifle the playing response.

I found some small steel tubing I scavenged from an old vent line from
a gas valve that was just right.  Though the resultant inside diameter
was a bit smaller that the original, it did not stifle the response.

The larger vacuum nipples if broken, can also be replaced with 1/4
copper tubing, for a perfect pressure-fit..  Use a piece 3/4" long.
Insert only 3/8" into the block. Place a 3/8" piece of shrink tubing
over the exposed end to increase the outside diameter as needed.

> There's no easy access to drill out the holes, due to other parts
> above the valve blocks, and it's nearly impossible to remove the
> valve blocks from the one-time clamp washers that hold them to the
> frame bottom.

Use a small sharp chisel or screw driver to pry a side of the Tinnerman
speed nuts up from the frame.  Use a small diagonal cutting pliers -
make one cut on the nut where it is thinnest.  Gently remove with
needle nose pliers.  Do not destroy, as they can be reused, even after
being cut!  Or, the bottom of the strikers can be threaded with a 7/16"
die, and bolted back on.

> I'm hoping that Tom Lear or Michael Stehney are still around and
> will reveal their secrets of removing valve blocks from the frame.
> And of disassembling a valve block, though I don't know that it will
> be necessary except to reduce the valve travel and save air and
> speed up repetition.

It will be necessary to disassemble each block unit to reline the top
of the valve.

This will give a better seal and reduce the travel just the right
amount.  All that is required is to glue a 1/2" round of 3/32" gum
rubber sheet.  Care must be taken to use the minimum amount of glue
evenly applied to avoid warps in the new seal.

Further detailed information about how to disassemble the striker
units will be forthcoming.

> I wish there were some way to stop rewinding once it's started, to
> save the roll or just to go back and play some part over.  But the
> mechanical flip-flop arrangement between the rewind pneumatic and
> the roll feeler on the take-up spool won't allow for that.  Any
> ideas?

There is a way to defeat/re-set the rewind micro switches.  More on
that in the future.  It's sort of involved.

See above re Rewind.

Tom Lear
San Francisco, CA