idiot question!

[escin]

erm..this might be stupid.what happen if i put the secondary of transformer to wall plug as input and it's primary to the output.

 

[pebe]

A big BANG!!!!!

 

[escin]

wow!!!true?

 

[Nigel Goodwin]

wow!!!true?

Yes, depending on the voltage of the secondary winding it's most likely to blow the transformer almost immediately.

You might, or might not, actually get a big bang - but the transformer will be destroyed.

 

[stevez]

While applying voltage well in excess of the winding's ratings won't work you can reverse the transformer, so to speak, and apply an apppropriate level of voltage to the secondary. My first shortwave radio had a home brew isolation transformer consisting of two 120/12 volt transformers - voltage was dropped to 12 volts then applied to the secondary of the second transformer yeilding approx 120 volts out.

 

[pike]

Why would any one be as stupid to do this? In saying this, i mean this is an idiot question!!

 

[Nigel Goodwin]

Why would any one be as stupid to do this? In saying this, i mean this is an idiot question!!

You wouldn't believe the stupid things people do!.

For an example:

Pace Electronics used to manufacture an analogue satellite receiver, called the MSS1000 - it included a Dolby Pro-Logic decoder and amplifiers internally. The speaker connections on the back used the standard push spring connectors that amplifiers usually use, and the mains lead was the normal 'figure 8' plug in lead.

The customer brought the unit in for repair, I repaired it, and he later collected it. The next day he brought it back saying it didn't work!.

What he had done was cut off the moulded 'figure 8' mains plug, strip the wires, and connect them into one of the speaker sockets - 240V directly into the speaker output of an amplifier!.

As you can imagine, the amplifier didn't like this at all, and he ended up paying for a new amplifier/decoder PCB.

BTW, the gentleman in question is a highly paid advertising executive, this was at his country home, he also has a home in London as well, and perhaps others - I only know of these two.

Connecting a transformer backwards seems fairly 'normal', we probably wouldn't even laugh about it :lol:

 

[ChrisP]

I know of a company who designed, manufactured, and shipped PCI parallel port boards with the pinouts reversed side-to-side ("A" side for "B" side) on the cards. This had the immediate effect of crossing various signal lines with operating voltage lines when the card was installed and the system powered up... How did that get through testing and QC?? Or... was it discovered, but the "bad" cards shipped in error??