Fixed a 1980s oscilloscope that was trying to kill itself

I was in my home shop last Tuesday, testing a board from a Commodore 64. I had my old Tektronix 465 on the bench. I turned it on and heard a loud pop, then saw smoke coming from the back. The screen went dark. I unplugged it fast. I opened it up and found the main filter capacitor had blown its top. It was a 2200uF part, and it had leaked all over the board. I cleaned the mess with isopropyl alcohol and a toothbrush. I had to order a new cap from Mouser, which cost about eight bucks. After I put it in, the scope powered up clean and the trace came back. Has anyone else had a vintage piece of gear just decide to end it all like that?

2 comments

2 Comments

beth_hart689d ago

Wasn't that cap more like 2200 microfarads?

henrygrant9d ago

Hold on, you're blaming the scope? That capacitor was a ticking time bomb from the day it was made. Those old electrolytics dry out and fail, it's just chemistry. The scope didn't try to kill itself, it ran perfectly for forty years until a cheap part finally died. Calling it a suicide is dramatic. It's just basic maintenance on old gear, like changing the oil in a car.