07-06-2013, 06:25 PM
These are starting to appear as people clear out their attic. A logical expansion, the Interface 1 provided interface for the ZX Microdrive as well as an RS232 port and two outlets for the Sinclair network system (up to a max of 64 connected computers) that allowed other computers to share Microdrives and printers. The ULA inside was quite clever, without an interface 1 connected the computer would generate an error code if Microdrive commands were typed in, using the NMI data line to do the honours. The ULA on the interface would step in on detection of the NMI, check if the error related to a Microdrive operation, if not it would hand back to the Spectrum, if a Microdrive command the ULA would run it's routine by suspending the Spectrum ROM and accessing its own, then on completion hand back to the Spectrum. All very clever and a lot of fun if it decided to have an off day.
This example was in good nick and did not have the tell tale circular mark of heat damage just in front of the edge connector. If you find one like this, give it a wide pass as the ULA inside has gone belly up and melted the plastic case. Inside, no surprises other than balls of fluff and dirt and the usual extra patch transistor on flying leads. One job that has to be done with the lid off is cleaning of the Microdrive edge connector.
Lid back on, connect up and test. The original Thorn-EMI diagnostics data books for the Spec and interface units is available as a download from World Of Spectrum and is a recommended start if you are going to start servicing these computers.
This example was in good nick and did not have the tell tale circular mark of heat damage just in front of the edge connector. If you find one like this, give it a wide pass as the ULA inside has gone belly up and melted the plastic case. Inside, no surprises other than balls of fluff and dirt and the usual extra patch transistor on flying leads. One job that has to be done with the lid off is cleaning of the Microdrive edge connector.
Lid back on, connect up and test. The original Thorn-EMI diagnostics data books for the Spec and interface units is available as a download from World Of Spectrum and is a recommended start if you are going to start servicing these computers.
