This scope has the famous "FAIL ++ Acq" error which points to the infamous failed (and leaking) SMD caps on the acquisition PCB.
I'm moving on to troubleshoot another (unrelated, I think -- and hope) issue.
During the 25 second "on" period, relays click on & off, the monitor goes through it's boot display (all bright, then dark, then the clock icon), then the graticule is drawn, which is quickly replaced with the "Tek Running Autoing" display listing the "FAIL ++ Acq" error.
During the power-up period, the front panel LEDs all turn on for about 25 seconds, then off for 5 seconds, then only the CH 1 LED lights.
The service manual says (in the Front Panel troubleshooting chart):
Do all of the front panel LEDs turn on and then turn off a short time later?
(Then:)
Does one front panel LED turn on and then turn off, followed by the next LED until all LEDs have turned on and then turned off?
The LEDs do not go through this one-at-a-time sequence. The manual's flow chart points to a failed CPU PCB if the LEDs don't blink this sequence.
Can someone with a TDS4xx confirm power-on LED behavior?
I'm trying to determine whether, because the LEDs aren't blinking "properly" and most of the front panel buttons are not working (the buttons bordering the monitor, plus all the CH input buttons), does this mean a replacement CPU PCB is in my future, or if it's possibly related to cap failure (ie, other cap failures beyond the acquisition PCB)?
Has anyone else here have a similar problem (non-functional buttons) in the past? I'd appreciate hearing your experiences.
Thanks, Dave