Cumana Disk Interface
This is an annotated version of the Cumana Disk Interface schematic
Important: Note that the schematic has a small error regarding the connection of the Cumana voltage rails (5v/0v) to Oric's expansion port (P1) at pin 33/34. THERE IS NO CONNECTION between the 5v and 0v rail of the disc interface and pins on the expansion port as shown! Not even for a common "digital ground", as you might expect.
A common connection is of course required, but it is not explicitly shown on the schematic. The PSU in the Cumana unit feeds both the 7905 regulator (REG1) and connects to the DC Jack for Oric, so the common line is the "Vcc" (0v/+5v) labelled line. The PSU itself is not shown on the schematic (transformer, bridge rectifier etc.)
Pin 33/34 of the buffered expansion connector (P3) do connect to the Cumana 5v/0v rails to provide power for other peripherals.
The schematics, and scans of the bare PCB can be downloaded below.
- Cumana Schematic (JPEG 1.4MB)
- Cumana Overlay (JPEG 336KB)
- Cumana Top-side PCB (JPEG 577KB)
- Cumana Bottom-side PCB (JPEG 715KB)
Source, documentation and pictures © 2009-2018 Mike Brown. Visit the website at http://oric.signal11.org.uk for the latest version and contact details.