Re: Mellotron 4-track update
2009-11-12 by lsf5275@aol.com
So I have been working on about a half dozen projects at once but I am
nearly done with the 4-Track. I am going to post some more pictures on the Yahoo
site, but I wanted to share some information about what I have discovered along
the way.
As I said in a previous post, I think this could have been the best
Mellotron yet if it had reached the production stage, but there are a bunch of
screw-up that make no sense. It seems obvious that there were some shortcuts
taken here and the way some of the components are assembled doesn't make
sense.
I posted a little (self serving) video on You Tube that shows the method I
used to align the tape head, which were all over the place when I really took a
good look at them. None of the techniques I used are applicable
to a M-400. I think they will prove to be correct, but I'm feeling my way along
as I go.
So here are some photos and their descriptions. I will post them on Yahoo
later tonight.
Part of my shop. There
are 4 other Mellotrons down here, two behind me and two more in the
other room that are not in need of service (one being the M4000) The
pretty white one is #600, back for a new set of pinch rollers, a
little tune-up and a couple of mods. On the rack is the guts of
the (formerly blue) Mellotron and the 4-track main
frame.
The rubber on all of
the pinch rollers is in good shape, but notice that the rubber is
not glued to the hub. So if someone were to really crank down the
set screw, the rollers become egg-shaped as they turn. I may get
some rubberized CA glue and try and glue them to the hubs. Martin
was right, they are cheap shit... but
soft.
The pressure pad rest
is so low that even when the key is released the tape is in constant
contact with the pressure pad. I removed the spacer on each end
between the rods and the frame. This solved the problem.
The head block is
fixed. I used the piece of aluminum stock and the piece of spruce to
properly align all of the heads. Interestingly, Even if the center
heads are in perfect alignment with the tape guides, They are a
little off (a few thousandths) near either end. I adjusted the head
height the best I could and I think it will be substantially better
than it was. You can learn more in the
video.
The heads are all
pushed against the aluminum rail to get them straight and to zero
the azimuths. The same was done on the back
set.
The piece of spruce
was stuck back though the metal take guides and used to align the
spill box.
Oddly, there were no
felt isolator pads on either the pressure pad springs or the key
springs. Every time you depressed a key you got a nice click,
though. I will go back and individually adjust each pressure pad as
I install each key. The pressure pads were all bent up and no two
were the same. I made a some little wood jigs so I could get them
all the same. The short ones are bent a bit different at the tips
then the long ones so that they press properly against the
heads.