The only difference between the CTM640 and CTM644 models is the additional 12V power supply for the CPC664/CPC6128's disk drive in the later model.
With the arrival of the CPC664 and CPC6128 models, the existing stock of CTM640 monitors was sold out and later only CTM644 monitors were sold, even with the CPC464. For that reason, the 12V power outlet was designed as a socket for a cable coming from the CPC, while all other connections were made with cables coming from the monitor.
12V (CTM644 only)
The procedure of setting up the CPC with the CTM640/CTM644 monitors is described in the CPC computer's User Manual.
Service Manual / Schematics
Schematics and part lists can be found in the Service Manuals:
- Amstrad CPC 464 Service Manual - includes CTM640 schematics
- Amstrad CPC 664 Service Manual - includes CTM644 schematics
- Amstrad CPC 6128 Service Manual - includes CTM640 schematics
- Schneider CTM640 Service Manual (German and English)