Mellotronists

Here's my debriefing report after diving into the guts of an Orchestron:

It's bigger than I thought. Based on the pictures from various sources, I
know there are several incarnations of this thing, many times appearing as
some kind of anvil case with a keyboard on it, or two keyboards, or a
minimoog grafted in. This one is a single-keyboard version in a
wood-veneered case. You know the ARP String Ensemble, which in real life
seems to be a little bit bigger than it needs to be? This is very similar,
about the same width and height, but deeper by several inches. The end
panels are not 90 degree boxish but rather are cut at sleek and stylish
space-age angles like many high-tech gizmos of the 70's. It's a one-person
job to carry, but just barely.

The keyboard is of Magnus chord organ quality, with white plastic white keys
and brown plastic black keys. Touch is extremely light and fragile-feeling.
At the left is a control panel with three sliders (Reverb, Tone, Volume),
lighted Power rocker switch, pitch control adjustment, and a big
engage/disengage rocker switch thing for the optical disk drive. Along the
front on the right under the keyboard is an open area with shelves in it for
storage of disks. The disks are 12" in diameter, and come in LP record paper
sleeves. Along the front on the left under the control panel is the disk
drive bay.

With the drive control in the disengaged position, you can slide a disk in.
Moving the control to the engaged position does a couple of things: first,
it raises a pointed spindle that pokes up through the hole in the middle of
the disk, and second, it brings a rubber drive wheel into contact with a
rubber capstan mounted on a small (2 or 2 1/2" diameter) flywheel. The
perimeter of the disk is pinched between these two rubber wheels, causing
the disk to rotate. Not sure of the RPM's, it's more like an LP than a CD,
that's fer sure. The disk sits on a stationary bed of felt rather than a
rotating table, so I suppose this is a source of eventual media degradation.

The disks are made of clear plastic and have concentric black toner rings
that are the audio waveforms. Don't know the sequence, I would assume that
they are in chromatic order from inside to outside or vice versa. Above the
disk, deep inside in the back of the disk bay, sits a pickup head that spans
the tracks. Under the disk, under this playback head, is a long skinny
clear-glass incandescent light bulb with a single filament running the
length of it. Many times it's published that the Orchestron disks are "laser
read", but actually they are "incandescent read". No lasers in this box. Any
laser involvement would have to have been on the disk creation side.

I wonder what would happen if the bulb burnt out. I presume the bulb is not
totally custom-made, so that there is some hope of finding a replacement. It
kind of reminds me of the bulb in those lamps that you might see over a
music stand, or over a painting. Anybody have any ideas about this? Maybe
white LED's would work too? Or even red, depending on the pickup
electronics? Then I could make a non-burnoutable replacement.

Now about the sound. Compared to a modern sampler, it's just plain crummy.
Compared to a Mellotron, it's still crummy. You can hear pops and crackles
as you hold down a key, and there is a hiss from the pickup that's there
even if there is no disk in the machine and you play the keys (photonic
noise?). The different sounds bear a basic resemblance to what is labeled in
the center of the disk, but since they are looped you miss the attack
transients which often are important parts of identifying the sound of an
instrument. The overall fidelity is kind of like a transistor radio. That
being said, it does have a characteristic all its own, and I think that
there would be a lot of fun to be had incorporating it into a recording. The
disks with this one are Cello, Violins, Vocal Choir, Flute, Pipe Organ,
Hammond B3, and Saxaphone (sic). Also there are a whole bunch of Optigan
disks which are currently uninventoried and unexplored. Those should be fun.

This Orchestron was in a state of arrest upon first power-up, the main
problem being that the disk was not turning which of course is not a good
thing for Orchestrons. It turns out that the rubber drive wheel had a notch
burned into it by the motor shaft, which of course gets worse with every
second of power-up as the thing sits there eating away at its own guts. I
tried to move the wheel off the notch with my finger, but it just went
around once and fell back into the notch. It was not easy to get this wheel
out with its shaft, being somewhat buried deep within, but of course as you
may be able to tell by my enthusiasm about such things I was able to extract
it surgically. I mounted the shaft in my drill and spun it while sanding the
edge, and this got rid of the perimeter incongruity (while decreasing the
diameter slightly, naturally). It turns out that there is enough range in
the speed variation mechanism to make up for the pitch shift this repair
would cause. The pitch control consists of a long conical shaft on the
shaded-pole motor which the rubber wheel contacts, and to adjust the pitch
the whole motor in its mount slides so that the rubber wheel touches
somewhere along the conical shaft. It's a CVT. Once reassembled, the machine
was up and running in all of its crackle-spattered old-phonograph low
fidelity glory.

Someday I plan to take pictures and post them somewhere - got the digital
camera, got the flash card reader on the PC, now I just need the kids to
leave me alone long enough to do it :)

Best Regards,

- Gene

M400S #1023
M400S #1213
M400S #1289