Here I have a PRS-2026C Data Retrieval unit which is part of the GEC-Marconi (formerly Plessey Avionics) ESD2020 system used for fault diagnosis and servicing of the Harrier GR5 and the AV8B aircraft. These are no longer used by the air force and find themselves onto eBay and other military surplus sites. I was donated one for a teardown video so I thought I’d take a look inside.
This is actually just the Data Retrieval Unit which is carried around by the ground maintenance crews and connects to another box inside the aircraft. There is a hand held keypad and a 2×16 LCD screen to operate the unit. It is a single board computer system based on the Motorola MC68008 which is the 8 bit version of the MC68000 running at 8Mhz. There are two ROMS; one containing the real time operating system by Silicon Software and the other containing the application. There is also 1Mb of EEPROM storage for storing the aircraft engine data. There is 256Kb of SRAM to complete the main components. Aside from the usual UART and interface IC’s there’s some 74 series glue logic and a couple of CPLD chips.
There’s no video output on this unit and data is sent to / from the aircraft over RS-423 with Manchester encoding. The keypad and LCD communicates via RS422. There are also 4 additional RS232 serial ports at TTL levels which go to a user port used for downloading the data to a PC and a printer. I also dumped the EEPROM storage and found some aircraft tail numbers amongst other data but most was meaningless to be honest.
Credit to Neil Roberts who also has one of these units and kindly sent photos of it working with the hand held keypad. It is easily powered as the board runs entirely off 5 volts and on the other side of the case there is a DC-DC converter which converts the aircraft 28V DC to the 5V required. It also has an optional 24V battery pack which was not fitted so I powered it up by connecting a bench PSU to the battery terminals.
Not sure what I’m going to do with it but it might make a great hacking project. Here’s a few photos and some YouTube videos.
Teardown video
Power up testing video