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I know you guys like to fiddle with capacitors so I thought I would share yesterday's experience and offer a teaching moment.

I rebuilt an old Wavetek Function generator recently. Mostly, I replaced the electrolytics. After powering it up and seeing it did not work, I shut it down and put it away for another day.

Yesterday was another day...

I noticed that a few of the electrolytics were not replaced, so I replaced them. I also noticed that a couple of fuses were blown--replaced them.

Then I flipped the switch with my o-scope monitoring the output. Hmmm, I get a sine wave with a lot of 60 Hz interference---maybe the pwr supply has a problem...I lean back in my lab chair and...POW-POP-SMOKE-ELECTROLYTE SPLATTERED ALL OVER THE PC BOARD.

I hit the switch and fanned away the smoke.

Further study indicated that I had installed a 1000uF 35V cap backwards (wrong polarity).

I replaced the cap using the proper polarity, hit the switch and quickly retreated a couple of feet and waited. No POP, no SMOKE.

I got enough courage to move closer and check the output with the o-scope.

Yihaa!! Sine wave looked good (2nd and 3rd harmonic down 40db and no 60Hz interference).

Lesson: POLARITY MATTERS

(Of course, I knew this, but on that one cap, I was careless).
 

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Yes.... polarity matters.


How do you replace electrolytic fluid?
 
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