Transformer problems...

[Boscoe]

Just puzzled me this one a bit. I have this toroidal transformer that I got from an old power amp that I intend to use on a new project but the voltages are way too high so I intend on taking a few windings out. First I powered it up to see exactly what the rail voltages were but I just get the sound of it melting. I immediately turn in off. It was only on for less than a second my finger was still on the switch. I check the windings to make sure I get the right ones, although it has no info on which ones which I assume that the primary windings are the ones with a much smaller gauge wire then the secondary larger wire. I have made sure I'm not powering the 110V winding either. There was a tiny winding on top of the primary and secondary but this had only 20 turns with a tiny gauge which I have taken off.

By the size of it I would guess it would be about 1000VA although I wasn't using any soft startI didn't think I would need it for a little bit of testing. Could this be the problem?

Thanks.

[simon7000]

Power it up from a low voltage transformer around 12 volts. Then you can measure all the windings voltages and see what is who, when and where!

If it still heats up, use an oscillator and resistor to find the shorted winding. The one that has the least difference between DC and AC resistance and impedance is most likely it.

[Michael Bean]

Use a "light bulb" tester, 100 watt bulb and no load on transformer. If all is OK, bulb should light at first, then go dim or nearly off.

Mike

[Boscoe]

Nice one thanks folks.

[AndrewT]

get into the habit of always keeping the bulbtester right next to your workbench so that you never try to start a part assembled project direct off the mains.

[44250]

I´ve always used Ohm-meter to mesure active resistance of the transformer coils. The coil with greatest active resistance is commonly the 220-Volt one(i live on a continental part of Europe and we have 220 Volt supply). Off course I would mesure before powering it up. The idea with bulb is the one that I like the most-it is cheap,sure and very simple! I will remember that one!

[Elvee]

Originally Posted by 44250

The idea with bulb is the one that I like the most-it is cheap,sure and very simple! I will remember that one!

It is indeed a very good one, but it will soon be over (or it already is, in my case):
the *$£* greens have succeeded in outlawing anything 60W or higher, and the rest will follow very soon.

Make sure to make huge stocks, otherwise you'll be caught naked, just like me.

[44250]

My country is always late in everything but in this case that is not so bad-we can still buy and use bulb-lights. If You need them,just give me number of peaces,power of light bulbs You need and your address at private message and I will send it to You. It is very cheap here and I can buy it "on every step". If I am not wrong,the flag at Your profile is a Belgium flag. I have a brother in Belgium and he is comming soon at vacaton here,so I can send it by him to You in Belgium. I would give him the bulbs and your address an he would post it to you. Greetings!

[Michael Bean]

Hi Everyone, while we're on this side track, you might want to look at this:

Phase-out of incandescent light bulbs - Wikipedia, the free encyclopedia

Mike

[Elvee]

Originally Posted by 44250

My country is always late in everything but in this case that is not so bad-we can still buy and use bulb-lights. If You need them,just give me number of peaces,power of light bulbs You need and your address at private message and I will send it to You. It is very cheap here and I can buy it "on every step". If I am not wrong,the flag at Your profile is a Belgium flag. I have a brother in Belgium and he is comming soon at vacaton here,so I can send it by him to You in Belgium. I would give him the bulbs and your address an he would post it to you. Greetings!

Thanks, it's very kind of you.
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