Mellotron Schematics

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njm

Well-known member
Joined
Oct 16, 2010
Messages
116
Location
London
Anyone got schematics for the mellotron M400? Got buxx coming out of unit in the studio and wanted to check the PSU circuit, looks it's been modified a bit...

Cheers
NM
 
Both Streetly (in England) and Mellotron Archives (www.mellotron.com)(in Canada) are still in business. The guy who runs the latter saved Mellotron from death and bankruptcy court from "Mellotron Digital" check them out, they can probably hook you up. I think Mellotron.com sells a service manual.
 
I just rebuilt/recapped the PSU for a '74 M400 last year.

http://egrefin.free.fr/images/mellotron/M400.pdf

Page 16.

Not sure what kind of controller card you have in yours, but if you have the upgrade that Streetly and Markus (mellotron.com) sell, you won't need to worry about the upper leg of the PS, IIRC.

You may also want to subscribe to the newmellotrongroup on Yahoo Groups for additional assistance.
 
Thanks a lot guys! Love the cover for that manual, funnily enough our mellotron has a note on it saying no drinks and no fags....

Yeh it's previously had work done it by streetly. The PSU has a cap disconnected, a TO3 missing and the power diodes bypassed. Time to do a bit of reverse engineering. The controller card looks different too what I've seen in pictures. I'd like to have a go at sorting this buzz problem myself, you never learn anything if you get other people to fix stuff for you all the time.

This unit has an output trafo added too, looks like a OEM type in metal can, but the output jacks are still wired unblanced, is this a streetly mod?

Cheers
Nick
 
Hi Nick,

You need to be sure on the card you have. Seems like according to your description, your 'tron has the newer card (not the CMC-10, that's the older one) or the upgrade SMS-3 or SMS-5 from Streetly or Markus. Like I said in the previous post, the newer card (or Streetly or Markus upgrade cards) have the upper rail leg of what's shown on the schematic (SKT 1, 5 and 8 ) on the card itself, not in the PSU. That may be why your PSU has been modified (and as you indicated). The original PSU had 5 big caps under the housing, the newer/upgrade card reduces this in the PSU to only two caps necessary as the others are, again, on the card. If the procedure was done right, there should be no hum. However, if the caps themselves were never replaced and are still the originals (at this point over 30 years old), they themselves could be the reason for the hum.

Unless you've previously experienced this 'tron having no hum, know that M400s are prone to hum relative to where they sit in relation to RF and other hash. Their 35 heads may also have ties to hum, too.

I don't know of any Streetly mods for output trannies on the M400.

For all of these issues and more, I would call Martin at Streetly and discuss with him to be sure. He's a good lad and will set you straight. Tell him Chris sent ya, I placed a big enough order with him last year; he should know me pretty well by this point! =)

Cheers
 
As a reference, I found Markus' instructions that may illustrate the rewiring that is necessary for newer type/upgrade cards and how they're retrofitted into the older 'trons having the CMC-10:

http://www.mellotron.com/tech.htm#SMS4/MR

Also, I just remembered: while you're in there anyway, you may want to look into the safety modification that puts the mains fuse(s) before the power switch, not after.
 
A Jacob E. deleted my message, because I posed a link where you can buy the Schematics. I don't understand this because Blue
Jinn also mentions a commercial link  www.mellotron.com. If someone needs help for the CMC10, I found a way to make it stable.
  I would add the schematics but I don't want to get into trouble . (copyright)
 
Aah - that's because we (by notorious tradition) don't consider selling schematics a legit game here. It would be alright to buy from MelloTron (whoever owns the name now) directly, but NOT from second-sources..

(..and btw, you're necroposting: Thread five years old..)

Jakob E.
 
Yes this thread is five years old!!! But I'm restoring Mellotron M400 Serial Nr 317. So this thread was interesting for me after five years. Because  I've been searching for the schematics.of the motor control-board. Maybe others will have the same problem in the future. Is it a crime to offer help?


 

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