I have an HP 8568B spectrum analyzer which went through shipping
recently. The display unit no longer works and it appears that the
CRT section is the culprit. I checked the HV and signals and on the
surface they appear OK. I did find some glass chips in the case
which leads me to believe the tube is damaged/broken. Taking the CRT
out is a pain. I can measure the filament resistance at about 4 ohms.
If the tube is cracked or broken, wouldn't the filament burn-up with
an infinite resistance??