For the record: the scope shows a correct time&date, so I figure the C-MOS battery can't be gone bad. And could a bad C-MOS battery really prevent the scope from powering up?
Again, if the scope doesn't start, there is the faint relay clicking, but nothing happens after that. No fan, no beep, the LCD stays totally black. I'd say there is no power supplied to the PC mainboard at all.
If the fans are starting, there is also a beep and the scope always fully starts without any kind of error message or otherwise uncommon behavior.
Again, to me it looks/sounds like "only" the soft-start of the power supply is partly broken, most probably because some capacitor involved there has lost its capacity to some degree.
Well it could also be the power on switch is worn since it is a contact based switch.
Power supply working and not working.. doubtful. Usually when a power supply on a PC goes, the issue is persistent since the caps cannot hold charge.
Now let me say one thing before you keep reading.
If the company is not yours, then the company has two options, fix it or buy new.
Do not waste to many cycles on Trouble shooting and repair as the company will not pay you the €2400 or anywhere close to that to fix it. If anything you get a good job and a pat on the back if you are lucky.
Since this is not yours and it is going to get trashed if it continues, i would disassemble and re-seat all the connections and change the CMOS battery regardless.
the Red LVD cable and the one ethernet cable. Also verify the SSD data cable is not bent so much that it broke (i replaced mine since i have SSD cables all over the place here).
I found in mine, the RJ45 port on the aquisition board, the contact pins were corroded (dull copper). a gentle filing to get them to be "shiney copper", reset the LVD connector flush and the problem went away.
The other thing you can do is clone the drive from magnetic to SSD. The power draw of SSD is less compared to the magnetic drive ( Lecroy supplied the WR series with Western Digital Black, 160 GB drive which the one that came with my WR66zi, pulls .58 Amps at 5VDC, this is average current.. start up current will be higher for a small time period).
SSD idles at .092 Amps (.46 Watts) with none of the inrush current of magnetic rotational media. Even at full tilt, max is .46 amps (2.3watts) while average is .4 amps (2 watts).
In the end, as an excercise for learning, yes but to save the company money. Don't as you will not get that split.