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what makes a power transformer go bad? Dynamics Plugins
Old 29th December 2010
  #1
what makes a power transformer go bad?

that's the question of the day.


i don't exactly understand. it's two windings of copper wire one for each phase right? magnets are involved correct?

so what about all that goes bad?


i got this transformer i broke out of a wal wart that gets voltage up to the transformer, but not through it to the other side according to my voltage tester even before the fuse.(though come to think of it that voltage tester came from radioshack. might be a good idea to get a real one.)

obviously the transformer died, but why?
Old 29th December 2010
  #2
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DanDaMan's Avatar
 

I hate to say this, but I think this is in the wrong forum. I think this should be in Geekslutz forum. But to try and answer your question, has the copper winding come undone?? What effect is the dodgy transformer having on your audio e.g. does it sound hi passed? I'll tell you what, look for a guy called Wavebourn on here and PM him. He's good with this kinda stuff. You can usually find him floating around the Geekslutz forums.
Old 29th December 2010
  #3
Quote:
Originally Posted by DanDaMan View Post
I hate to say this, but I think this is in the wrong forum. I think this should be in Geekslutz forum. But to try and answer your question, has the copper winding come undone?? What effect is the dodgy transformer having on your audio e.g. does it sound hi passed?

i agree it is in the wrong forum, but every time i post in geekslutz, nobody answers so i just stopped. i get way more responses in the so much gear so little time.

i don't think the copper winding has come undone any. it wasn't sending voltage to begin with because the power plug was mangled on the instrument side.(the part that plugs into the instrument not the wall)

so i cut off the power plug and stripped back the leads and tested. nothing. next i cut open the wal wart case carefully and removed the transformer and wiring, plugged it in and tested voltage. we got voltage going to the transformer from the wall outlet, but on the other side of the transformer where the wires got to the instrument it's dead at the tabs on the transformer before the fuse, before the wire.

i don't get it!
Old 29th December 2010
  #4
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Hmmm, neither do I. Like I said before, look for a guy called Wavebourn and PM him, he's good.
Old 29th December 2010
  #5
Gear Maniac
 

Probably a broken winding or connection to the windings -- rare but it does happen
Old 29th December 2010
  #6
just checked continuity from cable to cable both sides. the cables are good.

if it is a broken winding or connection to, i think this tranny's a goner. I'd probably ruin it trying to get at the connection.
Old 29th December 2010
  #7
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LeeYoo's Avatar
 

Small transformers, even bigger ones, have a thermal fuse embedded inside the primary winding. If the winding of the transformer has been hot, this fuse pops. Most of them are so deep inside that you can't replace them. This thermal fuse pops after a while with a secondary short, but also goes sometimes without any obvious reason. Measure the continuity of the primary winding. It should be a few hundred ohms or so. You will find that it is open circuit.
Old 29th December 2010
  #8
Quote:
Originally Posted by LeeYoo View Post
Small transformers, even bigger ones, have a thermal fuse embedded inside the primary winding. If the winding of the transformer has been hot, this fuse pops. Most of them are so deep inside that you can't replace them. This thermal fuse pops after a while with a secondary short, but also goes sometimes without any obvious reason. Measure the continuity of the primary winding. It should be a few hundred ohms or so. You will find that it is open circuit.

since the transformer is a big copper wire tab to tab, i should be able to test continuity from one side to the other for broken connections right?

if so, the there's a broken connection. i went tab to tab and got nothing.


checking ohms right now.

this transformer was in a wall wart like power supply for a korg electribe. it's pretty likely that it took a few bad spills over it's lifetime. so the broken connection inside is very likely.
Old 29th December 2010
  #9
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LeeYoo's Avatar
 

A power transformer has two windings.
The secondary low voltage winding is just a few ohms.
The primary (the one that connects to the mains) is a few hundred ohms.
If that one is open circuit (ohm meter), the internal fuse has popped.
Old 29th December 2010
  #10
i got no ohms what so ever. I'm assuming the internal fuse is done, and probably not worth replacing.
Old 29th December 2010
  #11
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Rick Sutton's Avatar
 

Quote:
Originally Posted by sameal View Post
since the transformer is a big copper wire tab to tab, i should be able to test continuity from one side to the other for broken connections right?
Actually, you can't measure from one side of a transformer to the other as there is no hard-wired connectivity. Signal is transferred via mutual induction, not direct connection (which is why they are an effective isolation solution in audio circuits). The measurements are taken across the incoming lines and across the output lines.
You may know this but I thought it might be best to make it clear if others are having a similar issue and will be reading this thread in the future.
As to failure, not only can a wire or fuse open/break but the windings can short due to a breakdown in the insulation on the wire which will effectively kill it also.

Hopefully I didn't screw up the explanation too much, but that's what i understand about them from years of guerilla electronics survival!
Old 29th December 2010
  #12
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Primary and secondary windings are well separated in power transformers for safety reasons, so insulation breakdown is very rare. Transformers have to almost catch fire before that happens. Easy to spot (smell). Most faults in power transformers is an open primary winding/thermal fuse. Have had hundreds of them during many years of servicing consumer electronics. Second thing was broken terminals when dropped.
Old 29th December 2010
  #13
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Rick Sutton's Avatar
 

Quote:
Originally Posted by LeeYoo View Post
Primary and secondary windings are well separated in power transformers for safety reasons, so insulation breakdown is very rare. Transformers have to almost catch fire before that happens. Easy to spot (smell). Most faults in power transformers is an open primary winding/thermal fuse. Have had hundreds of them during many years of servicing consumer electronics. Second thing was broken terminals when dropped.
Agreed. I was talking in a general sense including audio transformers (a classic example being 48 volt phantom breaking through the insulation on old V72 transformers). Thanks for the clarification!
Old 29th December 2010
  #14
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Sure. Audio transformers are made differently.
Advice for the OP is to go buy a new brick from the corner store, with the right voltage, stabilized, and with at least the miliamps of the old one.
Old 29th December 2010
  #15
Lives for gear
 

Money? Power? The lure of a low-cut load impedance? Who knows?... in the end, society is to blame. And the loudness wars... definitely the loudness wars.

Cheers,

Otto
Old 29th December 2010
  #16
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DanDaMan's Avatar
 

Quote:
Originally Posted by ofajen View Post
Money? Power? The lure of a low-cut load impedance? Who knows?... in the end, society is to blame. And the loudness wars... definitely the loudness wars.

Cheers,

Otto
I like your thinking
Old 29th December 2010
  #17
Quote:
Originally Posted by ofajen View Post
Money? Power? The lure of a low-cut load impedance? Who knows?... in the end, society is to blame. And the loudness wars... definitely the loudness wars.

Cheers,

Otto


if not for all that, then definitely for the strippers and coke.
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