Great description Gene!!
A few helpin hints here from back at CentChambCom:
The 'rivets' are indeed press-fitted bits. Now, mind you, I have never changed a
tape, but have been told it's a snap (was that a pun?). Anyway, the typewriter
notes next to the brass tape-feeder thingy say that the easiest way to feed a
new tape is to attach the new tape to the old one and let the pinch roller feed
it.
It is critical to have the tension on the rewind spool adjustment right or you
may get either rewind problems or wobblies - another thing to worry about other
than the pinch roller and push pad adjestments! I recommend adjusting the latter
two before fiddling with the rewind spool tension - unless the thing isn't
rewinding at all. Just hold the note down until it runs to the end then turn the
power off. Now you can do your allen wrenching - oh so delicately - say a 1/8 to
1/4 of a turn at a time. A complete 7 second tape pull takes a hair over one
second to fully rewind. Works okay for me.
I agree that the electronics are rather dodgy. I fitted my M2 with a
digitally-controlled sealed motor and have the tape rack leads (RCA plugs) going
straight to a modern rackmount pre-amp unit. I feed mine out the rear hand hold
slots. I can't remember if that could work with an M1. If you're not too worried
about the formica furniture, you could provide 1/4" jacks mounted either below
the keyboard or out the back with the RCA's connected on the inside to them (I
wouldn't hard wire to the jacks as you will want to be able to take the panel
off for servicing).
The pulleys for the rewind motor and spindle are based on movie projector
apparatus and include four spaghetti "belts". Richard Chamberlin (who did most
of the design work on the M's innovations including the rewind spindle/spool) is
quite an amateur film person and added that touch from his experience running
his movies.
I am not familiar with the extra pulley situation. My M2 didn't have pitch
control originally and my former M1 was the donor of my digital motor. Sounds
very Chamberlinesque, however...
Now back to you Gene in the field.
Vance (wondering if those video phones will collectable relics in a few
years....)
Gene Stopp wrote:
> And now a report from our embedded reporter in Gene's garage:
>
> The pictures in Frank's Mellotron book, Mark Vail's "Vintage Synthesizers",
> and www.mellotron.com pretty much cover what it looks like. (Same pictures
> at those three places, by the way.) In addition there is a good
> under-the-lid shot at the web site. The M1 I got does not have the remote
> unit and therefore does not have that extra add-on control box or external
> wiring harnesses.
>
> The cabinet is inexplicably short. I'm not sure what the intention was, to
> put it on a low table or maybe on top of the road case that it comes in, or
> what. Perhaps it was done that way to avoid blatantly copying the M400?
>
> Much in the way that the Mellotron M400 is really one assembly that drops
> into the wooden cabinet, inside of the M1 there is an assembly which is
> pretty much the entire machine. It exists in the center of the unit with
> airspace on all four sides. One major difference from the M400 is that the
> two motors are not part of this assembly but rather are mounted separately
> and independently. Yes I said two motors - one is a fixed speed AC motor
> (looking much like a reel motor from an old reel-to-reel). This has a pulley
> with a belt over it, to the big flywheel on the capstan (consult the picture
> at Mellotron.com), and a spring-loaded idler pulley near the motor. The
> other motor is on the right side of the machine (as you look at the
> keyboard) and has four skinny rubber belts running up to a fairly small
> (compared to the other one) pulley on a shaft that runs along the length of
> the keyboard under the keys themselves. This shaft holds the reels where the
> tapes are stored. The shaft spins in the direction that rewinds the tapes
> after a key is let up (opposite of capstan rotation), and there is one reel
> per tape (total of 35). The reels slip on the spinning shaft, with enough
> friction to be moved by the shaft if the tape is not taut. There's a
> setscrew in each reel to set this friction point but the tape has to be off
> of it (i.e. in the take-up bin) to get to it. So this is how the M1 returns
> the tapes, rather than using springs. Very compact, but it seems that this
> method takes longer to rewind the entire tape than the M400 method. This is
> a fixed-speed return, whereas the M400 snaps the tapes back however fast
> they will travel under spring tension.
>
> All over inside of this thing are paper labels created on a typewriter,
> taped on to various surfaces, containing all kinds of useful information
> about motor oiling, tape threading, take-up reel friction adjustment, pinch
> roller and felt pad adjustment, and so on. There is a tape-threading tool
> which consists of a long skinny brass "tape" about 6" long. There is an
> allen wrench behind a little clip which is used to adjust the take-up reel
> friction setscrews. There is also an extra motor pulley.
>
> On top of the main assembly sits the keyboard, which is mounted on a square
> aluminium frame. This is a wooden 35-note keyboard, much like the Mellotron,
> except that the low "G" is a real low "G" in that it has the cutout in it
> for the F-sharp rather than being like a "C" in shape. The cheekblock next
> to the low "G" has the corresponding shape to match. Interestingly, the high
> "F" has a straight side where the F-sharp would be, so all I can say is go
> figure. Again the pictures on the Mellotron.com site show this clearly.
>
> The keyboard can be removed by unscrewing four sheet metal screws which
> mount it to the main assembly. No knurled knobs, get your screwdriver buddy.
> The track selector at the right end needs to come out at this time as well,
> since it covers the fourth screw. As soon as you unscrew the keyboard, it
> pops up from spring pressure below. When you lift it off, you will see that
> there are no pinch rollers or felt pads on the keys, just the front and back
> adjustment screw shafts poking downwards. The pinch rollers and felt pads
> are attached to spring-metal "fingers" that are mounted to a bar that runs
> across the front of the chassis. Removing this bar exposes the tapes. At
> 1/2" each, the tapes are almost touching each other with AGO key spacing.
> There are comb teeth separating and aligning the tapes, but they are very
> skinny.
>
> The tapes appear to be riveted to both the take-up reel and the anchor bar
> at the rear of the chassis. I have not yet examined these rivets to see if
> they are perhaps simple press-fit things that can be removed (hopefully), or
> if they are the kind you need to drill out so don't even go there and ship
> the whole thing back to Upland. Like that's gonna happen....
>
> The heads in the headblock are 2-track heads. For any given head each gap
> goes to a separate output, so there are 2 outputs. The track selector has
> six positions:
>
> 1 and 3
> 2 and 4
> 3 and 5
> 4 and 6
> 5 and 7
> 6 and 8
>
> Output electronics is under the left-hand cheekblock. Four pots, tone and
> volume for both outputs. On/off switches for each output also. Under the
> cheekblock is a linebox, inside of which is the circuit board with some
> passives and a single chip (haven't ID'd it yet). The circuit board is made
> out of vectorboard. Definitely not a mass-production effort here. On the
> right-hand cheekblock is the track selector lever (once again seen at the
> Mellotron.com picture), power switch, and pitch control. Hey wait didn't I
> say that the capstan was driven by an AC motor? Yes indeed, behind the pitch
> pot there is another piece of vectorboard with some electronics on it
> (including a 3-terminal SCR-type thingey) so there is definitely some AC
> waveform monkey business going on here. The pitch pot behavior seems to be
> stable pitch for some of the pot's rotation, then a slight drop off, then
> the motor drops to half-speed or so and then stalls. So I suppose that the
> motor is intended to be slightly sharp and the pot set somewhere in the
> "slight drop off" portion. This theory is reinforced by the existence of the
> spare motor pulley with a note next to it that says "use this pulley for
> A-440". So, tuning is set by pulley size, eh?
>
> I've not yet been able to get a good listen to the sounds yet. The sounds on
> this tape set is an assortment of strings, horns, flute, and vibes. Standard
> set? Don't know. When I started to work on this machine there were two main
> problems - first, all the keys were out of adjustment so I could not get a
> well-played note anywhere. Second, the electronics seems to be gummed up or
> otherwise dirty so there is a high-pitched squeal if the volume is turned up
> at all. Long road ahead... I'll try to take pictures along the way.
>
> Best Regards,
>
> - Gene
>
>
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