Found that WS1 had died again. CPU fan seized up again.
Replaced and computer restarted fine. WS1 up and running normally.
WS1, the main computer in the PSL lab died last night. On reboot bios screen says that CPU fan died.
I opened the computer up and had a look. Bearings on main CPU fan were a bit stiff. I wiggled them a bit and it now spins, with some noise, when booted.
I'll order a replacement CPU fan KDE1209PTVX 12V, 7.0 W and replace pronto.
Also there was no backup of this computer. Almost all the stuff is kept in Git version control, but we should get these computers back on scripted backups.
Edit Sat Sep 8 18:28:19 2018: Rebooted and restarted frequency counter. Beat note has drifted off to 750 MHz. Will take a while to bring it back in.
Fan has been reordered, will arive Friday next week.