Thank you for you question. Unfortunately, we stopped production of the TDS2014 in 2006 and it is out of long term support. At this time our service group offers best effort repair as many parts are no longer available. I'll provide contact information for them should you want to pursue a repair through them. I've attached a copy of the service manual which provides troubleshooting. From you description I'd assume that the Acquisition/main board of the scope is at fault and will most likely need replacement. Main boards are no longer available for sale have been supply depleted for several years.
Tektronix/Keithley Repair/Calibration:
Web: https://www.tek.com/en/service-quote
Email: rmarequest@tektronix.com
Please let me know if you have any additional questions.
