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.
_http://www.youtube.com/watch?v=-RgDmI4tmQ8_
(http://www.youtube.com/watch?v=-RgDmI4tmQ8)
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.