Well after enjoying the new to me TDS744 after fixing the color issue, five days later it died. Upon turn it on the power supply would cycle on and off (the front panel LEDs would come on and off repeatedly every 3 to 5 seconds).
After further investigation found out the HV Power Supply was overloading the 25V supply as it tried to come up and the Main PS would shut down and repeat in an endless cycle.
By unplugging the connector to the HV supply then the system came up normally when turned on.
After some more in detail investigation of the HV supply I found the HV transformer pin3 was open which supplies the 75volts, no continuity between pin3 and pins 1,2 and 9. However, looks like pin3 was now shorted to the primary pin 4.
So I was hoping to keep the scope in the original configuration, i.e. not switch to a LCD display.
Will have to see if I get lucky and find a HV transformer (120-1930-00) for a reasonable price.
Interestingly the HV transformer might had been replaced once in the past judging by the solder connections.
I guess having 30 yr old TE you have to expect issues.
Tony