Anatomy of a WurliTzer Theatre Pipe Organ
A Wurlitzer Relay needs to be disassembled in the right order!
First remove the front glass windows and put them out of the way in a
safe place. The cover can be removed from the primary magnet/valve
box on the back of the relay. The sealing clamp blocks can be removed
from around the cables at the end of the chest. If you are planning
to completely rewire the relay you can now chop through the cables
and make everything else a lot easier, however I wanted to preserve the
existing wiring so I left the cables in place and worked around them.
Next remove the air manifold box from the end of the relay. This hides
some screws that you will be looking for later!
Remove the screws holding the relay pneumatic trays. These are found from the
back of the relay. There are three rows of screws.
One row is just above the bottom of the back board. One is just above
the primary box and the other is inside the primary box, but you can get
to those screws between the magnets and the valves.
Once all the pneumatic tray screws are out it is possible to pivot the trays
out of the chest, limited by the cable at one end. There may be some
resistance due to the gasket becoming welded to the chest but gentle
persuasion should overcome that. Taking each tray in turn, preferably from
the bottom, ease the tray out so you can access the
screws holding the contact rail to the tray.
With the contact rail separated the pneumatic tray can be removed and the
contact rail placed back into the chest. Starting from the bottom means
you do not have to hold the top rail up while you work on the tray below.
With the relay pneumatics out the way it is possible to remove the primary
box. Most of the screws are from the inside behind where the relay trays
were but there is also one in each end, as was found when the manifold was
removed. The inside screws are now relatively accessible but the contact rails
still need to be negotiated carefully with the screwdriver. Having removed
all the screws the box is unlikely to move easily as, again, the gaskets
have probably welded themselves to the chest. The seal around the air inlet
hole will also need to be broken and removed before you try and remove the
box. More gentle persuasion should get the box to move but it is still likely
to be a tight fit between the ends.
With the primary box removed it will be possible to see why it is not
a good idea to try and remove the whole back board with the primary box
still attached. There is a screw in each end of the back board hidden
behind the primary box. It is likely that there is a gasket stuck across
each end of the chest including the ends of the back board. This makes it
difficult to remove the back board but with determination and a long thin
blade it is possible to split that gasket away and get the back board off.
After removing the back board it should be possible to remove the top from
the top chest and the bottom from the bottom chest but there is no way to
get the centre top and bottoms out unless the cables have been removed,
which means you cannot replace the gaskets. The top and bottom are also
likely to have been gasketed over at the ends and be reluctant to leave.
This is about as far as you can reduce the chest
unless you cut the cables.
All the smaller parts, pneumatics, valves etc can then be stripped ready
for rebuilding in the usual way.
There is nothing very unusual about rebuilding the relay parts compared
to any other chest in the organ.
The secondary pneumatics are a different shape to other parts of the
instrument so a separate leathering jig
was made. As there are relatively few of these to do a simple construction
The secondary pneumatics are different from other examples I have seen in
the way the contact chopper bar was mounted. On other relays, including
the preset relay in this instrument, the bar is soldered to two pins which
are pushed into the front edge of the top of the pneumatic. In this case the
bar is soldered onto 1/4" wide brass strips
which are screwed to the top of the pneumatic. When the pneumatics were
cleaned off about half of them had holes drilled
to take the pins and the others did not. This may have been a change over
point in the production line or an experiment.
As usual it is mainly a matter of doing everything in reverse of the disassembly
Assemble the primary box with its pneumatics and valves first and attach
it to the back board which has already been replaced on the chest.
Before reassembly I cleaned all the contact bars and the contacts. The
bars were first lightly rubbed with fine steel wool then treated with
"Deoxit" and "ProGold"
chemical contact cleaner. The contact wires were only treated chemically.
With a support (ball point pen) held under the contacts they were wiped a few
times with the chemically impregnated wipes. It is unlikely you will get the
contacts making at the same point they were before so a clean start should
ensure they will work first time and then the design will ensure the wiping
action will keep them clean if they are used occasionally.
One critical operation that you do not have on other chests is aligning the
chopper bars on the relay pneumatics with their contacts. I first glued the
gaskets for the pneumatics to the trays. This makes it easy to ensure the
holes in the pneumatics are exactly over the holes in the wood. With the
gaskets in place they clearly mark the location of the pneumatics so I
glued the pneumatics precisely onto the gaskets. When I placed the tray
into the chest and attached the contact rail many of the chopper bars were
missing the contacts at one end or the other. This was fixed by unsoldering
the bars from the brass strip, at one end, warming the other end until the bar
could be slid to the correct position and resoldering the other end.
The other relay I attached the contact rail to the pneumatic trays first and
glued the pneumatics over the gaskets with a little adjustment to match it to
the contacts. Much easier. It will get a little awkward in the corner at the
cable end of the chest where you cannot move the tray out far enough for easy
access but it will still be easier that realigning all the chopper bars
As each tray was completed it is the easiest time to
adjust the movement of the pneumatics. First, before fitting the up-stop
rail, set the downward limit stop. This is set by the screw in the top of
each pneumatic. It needs to be set so that the pneumatic closes far enough
to ensure the chopper bar makes contact with all the contacts, with a little
extra movement to give the wipe action between the bar and the contacts. This is
also a good time to ensure the bar is parallel to the contacts so there is
simultaneous contact across all the contacts. Too little movement and the contacts
will not close. Too much movement will cause excessive wear on the contacts,
fatigue and broken contacts as the wires flex, and an increase in the time it
takes the contacts to open after the note is released.
With all the down stops adjusted the up-stop bar can be positioned. This has the
buffers on screwed rods that the pneumatics rest against in their open state.
These need to be adjusted to ensure all the contacts are open when the
pneumatic is up. The one contact on each block that is connected to the
power feed should be set slightly higher than the others so that it makes contact
first. It is acceptable for the power contacts to remain in contact with the
chopper bar in the up position but all the other contacts must clear. Too much
free space increases the time between when the note is played and when the
contacts close so the instrument reacts more slowly. There must be enough space
to be sure all contacts clear but no more.
Properly adjusted the relay is remarkably fast and responsive.
I left the top off the to relay chest until after the pneumatics were
installed and adjusted. Makes it a lot easier to work on it. Unfortunately
that is not possible for the lower chests.
After everything is adjusted the relay trays can be screwed into place.
The primary box cover can then be put on, the front windows put on,
after cleaning the glass, and then the manifold box and ventils reassembled.
Finally, when all the relays have been completed, the blocks that seal and
clamp the cables should go back in place.
One manual relay (the Accomp) took 14.5 hours to disassemble, including
stripping the valves and all leather from the pneumatics and gaskets.
Releathering, contact cleaning, assembling and adjusting took about 55
hours. In between I did about 55 hours of wood refinishing, but most
people would not go to that much effort.