I've had service calls on several T7300 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.
If you have any questions, please call me, Tom, at 260.348.5653. I am a HP Certified Technician trained to work on the DesignJet series printers since 1995.