3M 79 Schematics – Service Information

I’ve recently started working on a 3M79 24 track at Rainshadow Recording in Port Townsend, WA. It’s only been 35 years since I’ve worked on one, but it was like catching with up an old friend. Except I couldn’t remember all the details of this old friend.

So I looked online to find service information. Specifically I knew there was a problem with the capstan MDA, and I wanted to see what the output transistors were.

The only one I found was so poorly scanned, I couldn’t read much of it; including the part number for the transistor. Fortunately, when I got to the studio, they had a spare deck, so I could steal that transistor!

The studio also had their own service manual, so I borrowed it and have made much higher quality scans for anyone who needs them.

There are two PDFs, one the owner’s manual, the other, the 11×17 schematics. Feel free to download and use them to their best use.