Wall plug transformers: Useful in effects pedals?

[moid]

Hello everyone

It's Saturday night and I'm up late on my own, and in a moment of violence towards broken electronic devices of all kinds I dismantled a wall plug that had died on me and in taking it apart (purely for research purposes of course) I discovered it had four 1n4001 diodes in it (now gone to my spares bag), a 2200uF capacitor (probably not much use in effects pedals) and a massive transformer that weighs a lot (see image below). Is this colossus useful in effects pedal circuits or shall I just chuck it in the bin? Also if it is useful, how do I tell what sort of transformer it is and whether it is functioning? Thanks

[GibsonGM]

It may or may not be useful.   You could make a  power supply with it.   Or use it in some rack type thing later on.

You have to connect a cord to the primary (the thick red wires) and measure the AC voltage at the secondary (those thin wires).   You must know how to do that safely or you can kill yourself....  What was the rating of the transformer (from the cover)?  That will tell you pretty much the whole story.   First you need to know why it died..was one of the diodes blown?  Or is the transformer dead? (measure resistance of primary and secondary, see if either are 'open'...Do before trying to plug it in!). 

You'd have to rectify and filter the AC from the transformer, that is what the diodes and cap were doing.  Then run the resulting DC thru a regulator, if you want 'clean power'.

[moid]

Thanks for replying -  I wasn't going to use it for powering anything (I don't trust myself not to blow anything up!) I was wondering if it had a use in the audio part of a circuit - I had a feeling I had once seen a ring modulator schematic with a transformer in it? The plug cover itself just said it was 240v to 9v... there's no other info, not even a company name or logo.

I set my DMM to AC and stuck one probe on the large red wire and the other probe on the corresponding small wire and got the following:

red wire 1 - 0.192V
red wire 2 -0.269V

If it's just junk I'll throw it away...I just have a terrible hoarder problem for things that 'might' be useful

[mac]

If the core is really big, some 220v to 9v can be used in 1watt 12au7/12ax7 tube amps.

mac

[Hatredman]

If the transformer is damaged, you can still unwind it and use the wire to build a copper thingy for you Burst Box.

[PRR]

> a wall plug that had died

If it is dead, why do you want to "save" the dead parts?

Keeping dubious parts around is VERY bad mojo. A good 1N4001 is worth 4 cents. A dead 1N4001 wastes an hour or more of your time figuring out why a whole build is not working. Even if your time is only worth $4/hour, that's 100X waste compared to just buying a 1N4001 (in large bags of 1N4007, the only way busy builders should be buying rectifiers).

OK, probably only one of the 6 parts is dead. Can you figure out which one?

[lars-musik]

Just as a side note : The philosopher's tone calls for a 2200uF capacitor.

Gesendet von meinem Lenovo K33a48 mit Tapatalk

[anotherjim]

Resistance test the transformer windings. Diode test the diodes. Resistance test the cap.

Plug supplies like that usually fail due to....
... the output cable breaks close to the casing due to bending fatigue.
... a sneaky fuse, hidden in with the transformer windings, has blown.

[GibsonGM]

When you test the coils for resistance, check resistance between BOTH red wires, and BOTH small wires...they are 2 separate coils...each red wire is one end of the primary, and each small wire is one end of the secondary.

The resistance between the actual sets of coils should be non-existent (meaningless), and doesn't tell us anything.

What you're looking for is to see if the primary or secondary is burned out.

Don't know of any audio use for a trafo like that other than to provide power....for a reliable tube build, I'd want new/lightly used iron, myself....wouldn't leave it up to a questionable part from the junk box.     But they are VERY useful for powering rack stuff, things you may build later, -  IF not blown....

[Mark Hammer]

If one side of a transformer is shot, can the other side (whether primary or secondary) be used as a choke in series to filter ripple out of the AC from a "good transformer"?  Or is that too risky, unless one has enough knowledge to weigh a number of different factors?

[PRR]

> can the other side (whether primary or secondary) be used as a choke

Yes; but the two sides are very different impedance and resistance, not generally suitable for whatever problem you face, and still bulky. There's usually a better way to filter ripple.

A good primary *may* be better than nothing as a "pickup emulator". But really oversize for the chore.

[antonis]

It could be dismantled and make some excellent ultra low value power resistors..