I've had service HP designjet plotter repair calls on several T730 and T830 models with similar error codes. The last one was BA7E70E6. The 'B' codes harkens back to the day when I routinely saw this type of error on the old 1050c\ 1055cm models. I used to tell customers you have the 'error code of death'. In more technical terms, the Main PCA Board has a defective chip or routine call somewhere on it and needs to be replaced. Replacing the board has resolved the error for me.
The Main PCA is located on the left-hand side of the printer.
This board is the 'brain' of the printer: where all the processing and printer management occurs; control of the overall machine (digital and mechatronics) with the battery for Real-Time clock. Single function and Multifunction versions share the same Main PCA. Memory size is 1 GB.
The Main PCA also contains other elements with the following functions:
Battery: to maintain the internal clock running. The internal clock is used to remember the actual date, used for cartridge life counting and warranty accounting.
WiFi module: Attached to the top of the board with some plastic locators, provides WiFi functionality to the printer.
Buzzer: To provide acoustic signals to the user.