Why does nobody talk about capacitor reforming on old gear?

I pulled a 30-year-old oscilloscope out of storage last week and just plugged it in like an idiot. It ran fine for about 20 minutes then the power supply cap vented smoke all over my bench. I always knew about reforming but figured it was just paranoia. Now I have to replace six caps and the smell won't come out of my workshop. Anyone else learn this the hard way or am I just unlucky?

3 comments

3 Comments

ross.kim1d ago

The same thing happened to me with a Tektronix 465 from 1982. I was so excited to see it light up I forgot about reforming entirely. It ran for about an hour then I heard this low hiss and saw smoke curling out the top vents. I opened it up and one of the main filter caps had split right open. Now every time I walk into my garage I get a whiff of that burnt electrolyte smell and it reminds me of my own stupidity. Learned that lesson hard and I won't make that mistake again.

fionanguyen1d ago

Oh man, that smell is brutal lol. Just a heads up though, it's not really "reforming" on a scope that old since those caps are probably dried out beyond saving anyway.

fisher.jessica1d ago

Tbh I see it a little different though. Sure those old caps are risky, but I've had decent luck reforming caps in 70s gear if I take it real slow with a variac over like 24 hours. @fionanguyen makes a good point about dried out caps, but it really depends on how the scope was stored before you got it.