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Did I fry my DC power supply with AC? Answered

Hi yall, I was a very stupid person tonight, but I have learned from my mistakes.

In short I fed my DC power supply AC voltage INTO it,

I was working on a subwoofers power board this afternoon, trying to diagnose why it is continually blowing fuses, anyway later I finally figure out that the 8A bridge rectifier is visually burnt as well as two small ceramic caps near it, taking the most obvious route I replace them with the same spec parts and power on, no activity but its not burning fuses at least for now.

I usually have my multimeter connected right to my 40V old "Lambda" (crap brand) power supply on the same test leads, so I can get an accurate reading of how much power I am putting INTO the circuit. I rarely work on live circuits and should have known this.

I attempt to get a reading with the meter while the sub woofer is plugged in and turned on. Little do I realize that the meter and the power supply are both the same leads, so I am putting AC power INTO my power supply where it should only be outputting power.

I of course see the power supplys indicators light up and show a spike of the max 40V and then slowly dying down to 0 then I hear something fizzle and smell electronics heating up. I shut it off obviously after only about a few seconds

Now I cant even get it to power a lamp or LED, NO MORE POWER. Should I cut my losses and just get a new power supply or try and salvage mine?


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Reply 9 years ago

I opened it up, took a look at the board and by some miracle saw the problem. While I did supply to much power to it, it only blew one resistor, I scrapped its side, took a reading and then replaced it. It works just like old times now! Hopefully it lasts.