I recently bought a car radio and made a stupid mistake when I connected the radio to the car.

Apparently I reversed the polarity on the radio which made the radio go poof and smell awful.

After opening the unit I saw that one of the radial capacitors was busted (the top of the unit is not flat) Busted radial capacitor

Before ordering a new one, I noticed the surface mounted capacitors, they have a visible cross on the top, while other (smaller in size) capacitors don't have a visible cross on top. picture 2

They still look flat to me, so I can't tell if can expect them to work or not because all the surface mounted capacitors with this size (8*12mm) on this board have this cross visible.

I don't have an oscilloscope as I have read that this could help determine if the capacitors are busted or not without removing them from the circuit.

I have searched the internet for examples of busted aluminum surface mounted capacitors, but I haven't been able to find examples to compare with.

So my question is, can I expect these capacitors to still be functional?

I'm hoping I can get the radio working again by replacing the busted capacitor(s). Hoping this is the only damage made to the circuit.

** EDIT ** I really don't understand why this is a bad question?

  • 4
    \$\begingroup\$ the question is just fine. Omit the specific story and ask about what happens to aluminum caps if voltage is reversed. This way local beaurocrates will not have justification fkr closing the post. \$\endgroup\$
    – user76844
    Apr 24, 2017 at 4:19
  • \$\begingroup\$ Oh, no, if you could smell it that means you let out the magic smoke that makes the circuit work. \$\endgroup\$
    – SDsolar
    Apr 24, 2017 at 15:10

1 Answer 1


To answer your questions directly: Probably not. Electrolytic capacitors have an insulating oxide layer which serves as the dielectric. When you reverse the polarity, this layer is destroyed.

Secondary to your question, even if you went to the effort of replacing all the capacitors, chances are the board is probably still toast. Most ICs can only tolerate 0.3-0.5V reverse. If you applied the full voltage, you've greatly exceeded this, which they've alerted you to with the smell. The caps themselves won't smell unless they've vented.

  • \$\begingroup\$ Thank you. I'm going to try to replace all the capacitors and hope for a miracle. I'll let everybody know what the end results are. \$\endgroup\$
    – kawa
    Apr 24, 2017 at 19:24
  • \$\begingroup\$ @Kawa what happened ? \$\endgroup\$
    – efox29
    Feb 20, 2020 at 16:57
  • \$\begingroup\$ @efox29 BB ON was correct, I replaced all the capacitors, it ended up a waste of time and really hard. It’s a layered board with 3 or 4 layers. \$\endgroup\$
    – kawa
    Feb 20, 2020 at 17:03

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