Old school tech taught me a new trick about capacitor testing

I was talking to a guy who used to repair tube TVs back in the 70s. He told me he never trusts a capacitor until he checks it under load, not just with a multimeter. Said he learned that after getting shocked three times by caps that read fine cold. Tried it on a bad power supply I was fixing, and sure enough the cap showed 120V with no load but dropped to 30V hooked up. Has anyone else run into caps that pass the static test but fail in circuit?

2 comments

2 Comments

jake1913d ago

And that load test is what separates the real pros from the multimeter jockeys, yeah? I've had cheap electrolytics show perfect ESR cold but sag like crazy once they actually had to pass current. What kind of load did he suggest putting on them for the test, a simple resistor or something more specific?

margaretw413d ago

Right? Cold ESR means nothing, seen it too many times myself. He just used a simple high-wattage resistor, like a 10 ohm 10 watt one, let it cook for a minute and then checked the voltage drop.