Wrong voltage

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Zippy

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Sep 21, 2010
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I got a box today (ebay Germany, international boombox model), plugged it and it went up on flames :-O I took a closer look and saw it was preset on 120V. What the f**k!? Who the hell sells a box that's not set for the native voltage :annoyed:
The question is: Can the damage be fixed or is the whole box roasted? Maybe it's just the fuse that is burnt?
 

mmcodomino

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Replacing the fuse should do the job without any problems. That is what it is there for after all :-P

I am pretty sure it was not a grail, because you would double double check that before plugging it in ;-)

Come on, what box was it? :-)
 

Zippy

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This one: http://www.ebay.de/itm/110902701178
I bid in it Tuesday the 26th, went to a festival the next day, came back this Monday and I was surprised I won the auction. This Pioneer is rare on ebay Germany and I wanted to bring this one back to life but instead it went dead :sadno:

And it was literally burning, that shouldn't happen if it was only the fuse :'-(
 

mmcodomino

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Zippy said:
This one: http://www.ebay.de/itm/110902701178
I bid in it Tuesday the 26th, went to a festival the next day, came back this Monday and I was surprised I won the auction. This Pioneer is rare on ebay Germany and I wanted to bring this one back to life but instead it went dead :sadno:

And it was literally burning, that shouldn't happen if it was only the fuse :'-(
It was freaking BURNING?! :-O :-O
Oh my goodness, that really does not sound like a fuse issue.
You could be in really bad luck and someone bridged the fuse and you blew the whole inside of the box...OR replacing it just does the deal depsite the flames :-/ .
But it's not that bad - cause even though it's rare, this box is damn ugly :lol: :lol: ;-)
Take it easy, sh*t happens :-)
 

sony_apm_fan

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Apr 8, 2010
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Ouch, not a good story. :blush:

In theory the correct rated fuse should blow if the input voltage is too high, protecting the transformer from damage.

But, if the fuse is incorrect, or if doesn't blow then the transformer will most likely be damaged.

If you are seeing or smelling burning then it would suggest that the primary winding on the transformer has been roasted....time for a new transformer.

May have even cooked the capacitors on the power supply....

Hopefully no higher voltage was sent out from the secondary winding into the circuits..... :-)
 

Zippy

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This box ain't ugly at all - it feels pretty good in your hands. It's not big but you know it means serious buisness. Weighs a lot. square woofers 'n stuff. Pioneer. I was pretty excited to check ot out :-/
 

Superduper

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There IS a fuse but it's after the transformer and does not protect the primary winding. But all you guys immediately jumping on the blown fuse conclusion don't understand how fuses work.... Normal fuses work by limiting CURRENT. They do not limit voltage, nor do they limit wattage (power). Fuses are sized based upon expected voltage and expected current draw. Doubling the voltage through a resistive load will increase power consumption (watts), not current. In this case, the primary winding of the transformer probably overheated, shorted, and the flames probably due to the insulation around the transformer burning. First, it's almost certain that the transformer is toast. Hard to say what else was damaged and will also depend upon whether the unit was actually powered up (switch thrown) on the overvoltage condition. As the box probably poses an electrical hazard now, I suggest having a tech look at it instead of doing it yourself. (Or donate it to me..) :-O :-D In any event, it's a good thing you didn't pay too much for it.
 

TW5

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Jun 26, 2010
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Set it at the right voltage and plug it in again :-D
its probably a electrolytic cap that smoked
should be checked out
 

Brownlow

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Jul 15, 2010
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TW5 said:
Set it at the right voltage and plug it in again :-D
its probably a electrolytic cap that smoked
should be checked out
Not what I would recommend.......pass it over to a skilled serviceman, that way you're guaranteed to continue to enjoy your hobby. :-) :-)

Besides, going against the advice of the Super One is not a path worth pursuing. :thumbsdown:
 

sony_apm_fan

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Superduper said:
There IS a fuse but it's after the transformer and does not protect the primary winding. But all you guys immediately jumping on the blown fuse conclusion don't understand how fuses work.... Normal fuses work by limiting CURRENT. They do not limit voltage, nor do they limit wattage (power). Fuses are sized based upon expected voltage and expected current draw. Doubling the voltage through a resistive load will increase power consumption (watts), not current. In this case, the primary winding of the transformer probably overheated, shorted, and the flames probably due to the insulation around the transformer burning. First, it's almost certain that the transformer is toast. Hard to say what else was damaged and will also depend upon whether the unit was actually powered up (switch thrown) on the overvoltage condition. As the box probably poses an electrical hazard now, I suggest having a tech look at it instead of doing it yourself. (Or donate it to me..) :-O :-D In any event, it's a good thing you didn't pay too much for it.

Thanks Super...great explanation.

So there is basically nothing to protect the primary winding from this sort of failure? Or mistake?

I was sure I have seen fuses before windings in some boxes...but could be mistaken.

Either way, your explanation of how a fuse actually works is great and very helpful.
 

Zippy

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I tried it with batteries... and it worked :w00t: Does that mean the transformer is alright?
I also opened it up and I found a blown fuse. Maybe I'm lucky and that's really it :hmmm:
There's another thing though. The seller's description was a bit deceptive. It says "speakers are not in good shape. radio sounds clear." So while the radio reception is indeed very good it does not sound good at all. How could it with no foam surroundings whatsoever :thumbsdown:
 

mmcodomino

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Zippy said:
I tried it with batteries... and it worked :w00t: Does that mean the transformer is alright?
I also opened it up and I found a blown fuse. Maybe I'm lucky and that's really it :hmmm:
There's another thing though. The seller's description was a bit deceptive. It says "speakers are not in good shape. radio sounds clear." So while the radio reception is indeed very good it does not sound good at all. How could it with no foam surroundings whatsoever :thumbsdown:

That is good news! :thumbsup:
That means your boombox is good to go on DC :yes: .
Sadly the transformer could still be toast after all since it is only needed to reduce the 220V AC to 15V DC or whatever this model takes.
I would still go with the blown fuse theory though :yes: . If you did not have plugged in for long, a change of the fuse should do the job imho. ;-)
Glad the unit is still intact though :thumbsup:
 

tshorba

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May 10, 2009
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Zippy said:
I tried it with batteries... and it worked :w00t: Does that mean the transformer is alright?
I also opened it up and I found a blown fuse. Maybe I'm lucky and that's really it :hmmm:
There's another thing though. The seller's description was a bit deceptive. It says "speakers are not in good shape. radio sounds clear." So while the radio reception is indeed very good it does not sound good at all. How could it with no foam surroundings whatsoever :thumbsdown:
You need to read about these speakers and how they work, it is a strange design. From the listing photo the speaker has some issues with the dropped trim ring. Again these are not a standard type of speaker.

Do not plug into AC unless you have checked the transformer, if you do you are just asking for trouble.
 

woodnbox

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Oct 26, 2011
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Great news about it working on DC. Just run it off a DC adaptor. :-D
Forget about AC - that tranny is toast.
This confirms that the Primary has burned out - that was all the smoke - that thing would of been glowing.
Luckily the secondary has stayed ok & the powersupply survived.
Like i said forget about AC - now your priority is getting them speakers refoamed. :sin:
 

Superduper

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sony_apm_fan said:
Thanks Super...great explanation.
So there is basically nothing to protect the primary winding from this sort of failure? Or mistake?
I was sure I have seen fuses before windings in some boxes...but could be mistaken.
Either way, your explanation of how a fuse actually works is great and very helpful.
I looked at the PS schematic for the FA-C5 (next model up) which doesn't have DC and neither of the fuses (there are 2) protects the transformer primary winding. You just can't make a single blanket generalization for where a fuse might be located but I will say that in almost all cases, the primary is not protected. You need to keep in mind that prior to eBay, regionally distributed electronics, especially larger ones (unlike walkmans or cameras) are hardly ever imported. So an electronic device distributed in North America generally does not end up in Europe. With that, the protection components such as fuses are designed to protect based on the calculated max anticipated current based on the proper voltage applied.

In general, current consumption is based upon the boombox load so if the boombox draws more current from the secondary, it should draw more current from the primaries too. Therefore, protecting the secondary by extension should protect the primary windings too if the proper voltage is applied. Protecting the primary windings with fuses is a little more tricky and may require multiple fuses on multivoltage units. Consider this: On the secondary side, the voltage should be standard for that model regardless of input voltage. Therefore, a 5-amp fuse (on the FA-C5) in series with the secondary windings is correctly sized to protect the internal boombox electronics regardless of what input voltage is supplied if the voltage selector is properly chosen. In other words, if operated properly, the expected secondary voltage might be 18v regardless of whether the boombox is operated at 115v or 230v. However, if a fuse is sized for the primary, say 1-amp @115v, then that fuse would need to be 1/2 amp when used @230v and other different values depending upon what other voltage choices are present. As you can see... protecting on the primary side will increase the costs of manufacturing and complicates the circuit.

Going back to talking fuses, you will likely note that even though your boombox secondary is someplace between 12 and 20 volts, those glass fuses probably are marked somewhere between 2.5 to 5amps at 220 volts (or some other high voltage). As long as current remains below the rated value, the actual voltage makes no difference to the fuse at all. 5amps at 10 volts = 50watts. However 5amps at 220 volts = 1100watts!!!!! In either case, the fuse is within it's limits and should not blow unless the current exceeds the 5 amps. If the fuse is theoretically 100% accurate, it will blow when 51 watts are consumed with 10volts applied to it. But if 220 volts is applied, it will not blow until 1101 watts is consumed.

Now, in actual practice, applying more voltage generally causes more power to be consumed if the load is strictly resistive. Using Ohm's Law, we can conclude that doubling the voltage through the same resistive load will result in double the current draw and therefore, blow the fuse, right? In reality, it is far more complicated than that. When operated at low volume, a boombox can be very thrifty (.2 amps) and when blasting at the max, it might consume a whole lot more, maybe 3.5 amps or more (but less than the fuse rating). If you pump double the voltage to the boombox, it would consume twice the amount of current presuming the internal resistance remains the same. However, when operated at low to moderate listening levels like before, even at double the input voltage, a boombox does not consume nearly enough to blow the fuse (2 x .2a is only .4 amps). But the whole time, the boombox will be subjected to double the normal system voltage which could rise to 36-40 volts (or even more). Most transistors, resistors, diodes can handle the increased voltages well. Electrolytic capacitors on the other hand has limited voltage ranges (based on intended system voltage), and IC's usually have far lower max input voltages than 36 volts.

In any event, the transformer primary, if not open circuit, could be shorted. It is important to get that resolved, even if you never want to use AC again and intend to use only DC. The reason is that the AC jack remains available and sometime, someplace, maybe years later, somebody else could potentially plug it in, and if the primary failed short, then next time, it could end up burning down the house. When a transformer winding is overheated, the insulative qualities of the wire used in the winding has been compromised and if short or partially short circuited, readjusting the voltage selector to the proper setting will not fix that and still likely result in more fire
 
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