Unpolarized cord used in a device that expected polarized cord; is it doomed?

September 30, 2009 8:59 PM

Unpolarized cord used in a device that expects a polarized cord. Device no longer works. Doomed?

My girlfriend inadvertently plugged an unpolarized (either C7 or C8) cord into our Tivoli Model Two stereo. It worked for a day and then stopped. I love this stereo so I am pretty sad. A few questions:

What kind of damage have we likely done to the stereo? Would it make sense to try to have it repaired or should we give up and replace it?

posted by medpt to technology (8 comments total)

Is there a fuse holder on the back of the radio? if not then see if you can remove the cover and look for one where the power comes in. Very nice little audio device worth repairing.
posted by hortense at 9:11 PM on September 30

Looking at the back of a Model Two, it looks like you can also use a DC adapter. There doesn't seem to be a user-accessible fuse there, though there may be one on the internal circuit board.
posted by Burhanistan at 9:17 PM on September 30

I wouldn't actually expect that to harm the stereo at all, just slightly increase the risk of electric shock. Do you have anything else plugged into the stereo (other audio sources, I mean)? Did they work during the time the unpolarized plug was in?
posted by hattifattener at 9:20 PM on September 30

hattifattener: no other audio sources were plugged into the stereo. It was just playing the radio.

We assumed that using the wrong cable caused the stereo to stop working, but we just moved into a new apartment, so there are a few other variables: stereo was plugged into an outlet that we've never had anything plugged into before (but which a surge protector indicates is grounded); stereo was just moved across town, jostled a bit, etc.
posted by medpt at 9:28 PM on September 30

Polarization is mostly a human safety thing, your stereo can't tell you plugged it in backwards (unless there is another ground provided to the unit through say a grounded antenna). Especially considering it appears to use one of those universal external power supplies. So it's probably a coincidence the unit failed within a day of the cord mix up.

Before you spend any money getting it repaired check to see if you are getting the correct output out of the power supply. Either by swapping in a known good unit or with a multimeter. Also trying a different outlet wouldn't hurt; it is possible the wall socket is bad or, and this is common OMG moment when moving, the wall socket unbeknowest to you on a switch.
posted by Mitheral at 9:32 PM on September 30

SWEET. After a failed attempt to open the stereo and locate the fuse, I found an old 12V DC power supply, plugged it in, and HURRAY, the stereo came on!

I'm still confused at the cause of the failure when using the AC power supply, since there seems to be a consensus here that the unpolarized cord was benign. Perhaps there is an issue with the electrical outlets at our new place. I will be sure to use a surge protector with the stereo.

In any case, thank you all very much for your prompt and helpful answers.
posted by medpt at 9:51 PM on September 30

There is some electronic scenario that unpolarized can cause to be disasterous, but I too agree that a wall-wart style transformer shouldn't care. Unless it was a particularly bad switching power supply that for some reason couldn't take it.

Just the other week, I had a server taken apart for about a week. Prior to that, it ran for about 5 years. When I put it back together, two of the three power supplies went POP and blew smoke out the back. I theorize that there were caps in there that were fine being continuously energized, but once they discharged and were reconnected, they couldn't take it. Might have been something like that.
posted by gjc at 10:05 PM on September 30

Most likely your girlfriend had to use excessive force to get the non polarized plug to attach to the radio and broke a connection.
posted by chairface at 6:49 AM on October 1