Capacitor blew on an old Tektronix scope during a calibration job this morning

I was running a routine calibration on a Tektronix 465 oscilloscope at my bench around 9 AM. Had the covers off to check the power supply voltages when a 10 uF electrolytic cap on the HV board just popped like a firecracker. I mean it shot electrolyte across my workbench and left a scorch mark on the PCB. I shut everything down fast and let it sit for 30 minutes before touching anything. Cleaned up the mess with isopropyl alcohol and checked the other caps nearby. Four more were bulging at the top. I pulled the whole board and ordered replacements from DigiKey. These old scopes are great but the caps are all past their lifespan by now. Anyone else had a cap blow unexpectedly on vintage gear? How do you decide which ones to replace preemptively?

2 comments

2 Comments

lee6271mo ago

Man, that brings back memories... had a 20 uF cap blow on my old HP 1740A last year and it sounded just like a .22 going off. I usually just replace any electrolytics that are more than 25 years old on sight now, too risky not to.

margaretj401mo ago

Oh man @lee627 you're not wrong, that bang is unforgettable. I keep a bucket of old caps just for the sound now.