From the TekScopes mailing list:
I just finished a 468 that had a bad rom.
Just for the record, there is an error in the troubleshooting section relating to the testing of just the analog section of the scope. If the processor fails, you will have a hung up trace off screen on the left side of the scope.
The troubleshooting section states to disconnect the p3008 connector on the A12 trigger board, pull the p483 connector cable and jumper the pins. Then, on the A14 vertical mode switch board move the p307 connector to the p206 test mode port.
This places the scope in analog mode and displays ch1 & 2 chopped.
The only problem is that when you disconnect the p3008 connector, you kill the +5vs source that is used on A14 - p206. The +5vs comes from the power supply on the timing board and powers all the digital logic.
The work around is to use a jumper to the +5 on the interface A15 board (test point) to pin 3, 4, or 5 on the p307 cable to force it to 5 volts, then it will work. This applies +5 to the ch 1 select, ch2 select, and /xy select, and a ground to the /chop select.
I can't tell you how much time it took to find that out. Hope this helps someone in the future.
The bad rom was one of the gold top chips.
Regards, Tom