Three versions were made. If yours has a single octal plug, it is the late version.
Early:
http://mcc.berners.ch/power-amplifiers/MC240EARLY.pdf
Mid:
http://mcc.berners.ch/power-amplifiers/MC240MID.pdf
Late:
http://mcc.berners.ch/power-amplifiers/MC240LATE.pdf
I've had half a dozen or so over the years. I had no idea there was a "mid" production unit - I've certainly not seen one. I have had one of the early units.
Learn something every day. Great stuff there 62caddy.
I'm curious, does he have a similar set of pages for the versions of MC40 ? I tried searching his site, but cannot find it (nor can I navigate to the link you provided below without just clicking on what you provided).
Actually, I know of two different versions of the basic circuit, and two different versions of the power transformer - giving rise to (at least) three different versions of the amp (since these changes occur at two different serial numbers). I have no idea if these correspond to the three versions of the MC240 that he shows, since there are no schematics shown for those; I think not though, since all three versions of the MC240 seem to have the 117/125VAC line voltage switch.This was all I was able to find on the MC 40.
It appears there may only be one version.
http://mcc.berners.ch/power-amplifiers/MC40.pdf
I have the voltage switch and one preamp input socket.Which model do I have?