I used to own the rarest Mellotron ever made, the Mellotron 4 Track.
This post brings back memories of the sound and the repairs.
And the smell, and the smell! Warm, dusty oil! I don't know anything about the 4-Track model. Do tell!
There were only 4 of the 4 Track models made before the company went out of business. It wasn't the original company but the 2nd incarnation of the company, from my understanding.
The concept behind the 4 Track was that you could use a standard 4 track reel-to-reel to make your own tapes. Perhaps a good idea but a bit late as digital samplers began arriving.
Additionally instead of being able to select only one sound/track at a time you could combine/layer any combination of the 4 tracks. As you may know the older Mellotrons had a rotary selection knob only allowing you to select one sound at a time.
I was also given a blank, unpopulated voice card with the machine. It may had indeed needed it because one channel had an intermittent problem with one card. It was a simple double sided circuit board and I had considered copying it to have a spare but I eventually sold the machine to a guy on the East coast of the U.S. (I lived in Los Angeles at the time).
The 4 Track was very clean - no excess oil and dust. I bought it from the original owner, a guy named Jim Purol who used to do a show called "Jim The Mouth" (if I remember correctly) in San Diego, California.
He had 2 other Mellotrons, if I remember correctly.... an M300 perhaps and another....
He used the Mellotron for sound effects during his radio shows.
it was in surprisingly good condition. He had a custom case for it but I didn't buy it..... in hindsight I should have. It didn't have any major issues except that one channel/card. The heads were good and still aligned.