How to wire transformer

[avanc]

I have 2 sets of primaries and 2 sets of secondaries.

The primary is 110/220v. I understand I need to connect them in series to work with 220v, which I have.
Meaning that I'd get one red, one black and one with red+black. This red+black should be wired together and nothing else, correct?

On the secondary I need v-0-v. I was thinking doing the same there (series) would be correct, giving me v-0-v, but looking at a schematic it looks like it doubles voltage?

 

[Mooly]

The primaries are (most probably 😉) wired as you say.

The secondaries also go in series.

We remove ALL doubt by using a bulb tester in the primary mains feed. This allows the transformer to work correctly if you get it right, and lights the bulb if you get it wrong.

With the transformer powered up you measure the AC voltage of each individual secondary and confirm they are as expected.

If that is good then you join them in series and measure the voltage from 'end to end'. You should see double the voltage of what you just previously measured because both are now series connected and the voltages add.

If you see little or no voltage then you reverse the connections to one of the secondary windings and retest.

 

[avanc]

Once more just to make it clear in my tired mind; I take that primary red+black connection and dont use it for anything else. The only wires I'll be using is the red from one winding and black from the other winding?

Yes, I was going to build a bulb fuse - but I don't think the necessary bulbs are available anymore, lol. Can only find energy saving bulbs.

 

[Zen Mod]

maybe this will help

 

[Mooly]

That's it, the primary connection to the mains goes nowhere else, and neither does the 'join' between the two windings.

 

[Moderation Team]

All the OT posts related to the original question have been moved here:

http://www.diyaudio.com/forums/powe...own-transformer-can-reversed.html#post5020556

It is to be hoped that if the OP is still unsure, or has any more questions then he will return and ask away.

 

[AndrewT]

Once more just to make it clear in my tired mind; I take that primary red+black connection and dont use it for anything else. The only wires I'll be using is the red from one winding and black from the other winding?

Yes, I was going to build a bulb fuse - but I don't think the necessary bulbs are available anymore, lol. Can only find energy saving bulbs.

any tungsten filament light bulb has the required Positive Temperature Coefficient (PTC) to allow the initial low current to pass and stay relatively cool (a very dull glow).
If the current is too high then the filament heats up and becomes a brighter glow. This increases the resistance due to the PTC effect and thus dissipates more heat and becomes a bright filament. (Don't use a carbon filament, if you could even find one).

The old filament light bulbs and the new halogen (power saving) lights bulbs are all this PTC type.
I keep a range from 25W to 150W and start with the lowest for testing a transformer wire up and for attaching the bridge rectifier.
Might need to increase by one power step when attaching the smoothing capacitors, because they draw a current for a bit longer heating the filament a bit more.

If the bulb goes to full bright, it means the voltage dropped across the filament is virtually at the mains voltage. The remaining voltage applied to the transformer is usually less than 10Vac, for a 240Vac supply. That means the secondary voltage is usually under 2Vac. After accounting for the rectifier drop.
The load on the rectifier sees <3Vdc and this rarely damages the equipment.

Since I started using the Mains Bulb Tester, I have found that the downstream equipment never gets damaged at start up, no matter how bad the wiring error. I recommend this to every Builder.