installing caps backwards

[technicolor]

i screwed up and misunderstood reading electrolytics. So, net result i installed a bunch of caps backwards on the astro sonic.

The set of course smoked and shut off. Is it toast? should i even bother replacing the cans properly? Or did i now fry the whole chassis?

[mstaton]

No you probably dd not fry anything except the caps. Just start over. The black line/mark on the caps are negative

[technicolor]

Originally Posted by mstaton

No you probably dd not fry anything except the caps. Just start over. The black line/mark on the caps are negative

well that's good news. This pig may be resurrected after all.

[radiotvnut]

Had it been modern chinese garbage, it would probably be ruined; but, the old stuff is more forgiving. Even if you did fry parts, it's likely still worth repairing and the damage probably won't be that extensive.

On new capacitors, the negative lead is almost always indicated by an arrow with a "-" symbol inside the arrow that points to the negative lead. Older capacitors often have different markings; but, almost always have some indication of the "-" or "+" lead.

[zeno]

We used to do it on purpose. The old US made hard plastic ones
worked best. Had a 50 amp supply we used. The higher the mfd
the better.

Oh if you didnt figure it out they explode quite nicely at times.
Trouble is they stink up the shop badly & the boss gets pissed.
Told him it was a FBT, it was one of those "yeh right" moments......

73 Zeno

[Rod Beauvex]

Incidently, PCBS can be labeled incorrectly, as can schematis, so make sure you double check those when in doubt. Try to take note of the orientation in which they were removed. And when in doubt, use a continuity tester to identify grounds.

[Electronic M]

I had a Zenith 5r086 or some such where the chassis shelf unscrewed easily, but the bolts which held the chassis to the shelf were recessed and nothing I had then could remove them. The cardboard lytic was mounted above chassis and I was able to replace it without removing the chassis, but the replacement exploded! Well I replaced it with the same voltage as the original, and figured the original must have been under rated and installed one rated for twice the voltage and it too exploded. Well later on I was able to get to the underneath of the chassis and found that a rubber connecting wire with disintegrated insulation was shorting AC line voltage to the filters! I corrected that, replaced the lytic again and all was well.

I once rebuilt a cap backwards in my color Admiral. It COOKED a HUGE power resistor, but all I had to do to fix the problem was reform the cap on my Heathkit C-3 reconnect the cap the right way(easy to do as it was the only cap in the rebuilt can), and replace the power resistor.

Me and my friends used to blow up old lytics from parted out stereo equipment all the time. Twice or more the rated voltage of AC on a lytic makes for some great fireworks! I'd set them off by the garage pointed at the street and the metal cans would often launch well across the street on the bigger lytics.

About a month back I over heard a classmate in one of my EE classes discuss how one of his friends "would put reverse voltage on large capacitors and measure it's effect on steel doors".

PS: I have been F^CKED up more than twice by errors in Sam's folders for more than one set. They are a great resource, but they are NOWHERE near infallible.

[radiotvnut]

A friend, who took electronics in highschool during the '70's, said that one of his classmates placed a large cap inside the storage area by the bench (each spot at the bench had a small storage area covered by a wooden door), plugged the cap into the AC outlet; and, within a few seconds, the cap exploded and literally blew the door off the hinges.

[CoogarXR]

I've told the story before about working on an LCD TV, hot, with the power supply unscrewed (yeah, yeah, I know). I was probing around and knocked the power supply off its studs and it fell flat against the metal screen backing. POW! Several caps launched off, one hit me right in the lower lip. That hurt more than being punched. I had a big bleeding knot, heh. How embarrassing. Just glad it wasn't my eye!

[N2IXK]

Originally Posted by radiotvnut

A friend, who took electronics in highschool during the '70's, said that one of his classmates placed a large cap inside the storage area by the bench (each spot at the bench had a small storage area covered by a wooden door), plugged the cap into the AC outlet; and, within a few seconds, the cap exploded and literally blew the door off the hinges.

We did similar stuff in our HS electronics lab. The outlets on the workbenches were all controlled by an emergency kill switch, and were powered down at the end of each day. At the end of class one day, after the power was shut down, we stuck a few electrolytics into the outlets and then left.

When the power went back on the next morning, things got kind of exciting.

The time we did the same thing with a selenium rectifier was even better, though. Cleared out several classrooms with the stink...

[dtvmcdonald]

Selenium rectifier story:

When I was a freshman in college people said "he's fixed more radios
than you've turned on" and it probably was true. A good friend
said his radio was kaput, could I fix it? So I went to his room,
took one step inside the door and said, correctly, "your radio has
a very very bad selenium rectifier". (He was an ee major, I was
chemistry). I'm surprised he wasn't in the hospital. I nice new Si
rectifier (these were just beginning to replace Se at that time) fixed it.
It took weeks for the smell to get 100% out of all the furniture.
The caps had survived the bad Se.

Doug McDonald

[Zenith26kc20]

For New Years eve I put about 10 800mfd/450 volt electrolytis in parallel and made a voltage doubler fed by a 60 watt lightbulb to slow charge them to about 300 volts. Dropping a empty beer can on the rails connecting them would make a blast louder than a gunshot, destroying the can completely.
Around midnight, the police came from a neighbors complaint to see who was shooting a gun. He was sure he had the culprits when he saw us laughing and cutting up. When he asked "who's got the gun", I dropped a beer can on the electrolytics. Needless to say he was NOT amused but realized he couldn't do anything more than tell us to stop. He did jump back FAST!
Putting the pack in a plant for Halloween and dragging a screwdriver across it with a string worked great scaring the neighborhood kids!
Finally one of the electrolytics shorted and blew the vent plug. NASTY!
As I look up there is still one of the 800's on my desk...

[Charlie]

Originally Posted by Zenith26kc20

For New Years eve I put about 10 800mfd/450 volt electrolytis in parallel.....

Man, next time you decide to do that (which I hope is soon), make sure to get a video and post on youtube!!

I installed a lytic backwards years ago in an AA5 radio. It blew... big time!! I crapped all over myself! When I opened the radio up, it reminded me of the mess that cat left under the chair after chewing the Christmas tree lights! Talk about had quite the mess to clean out of there.

If that cat had nine lives, he done spent them all!

[Reece]

Wild stuff! Technicolor: re: confusing markings on modern electrolytics. Look at the ends where the wires go in. The negative wire connects to the outer aluminum can and the can end is exposed at the negative end. The positive end has a fiber insulator and you don't see the can.

[N2IXK]

And on radial lead caps, the longer lead is generally positive.