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Transformer Wiring Query (Dual Secondaries)

post #1 of 12
7/24/11 at 6:18am
Thread Starter 
It's the moment of truth for my Sigma22 power supply, except I can't figure out the blasted wiring from the transformer. It's a dual secondary toroid (2x 0-18v) with a black/white pair of wires from one secondary and a red/yellow pair from the other.

The S22 has a four-way terminal block for these wires with two slots for ground wires. I gather that, if I connect things back-to-front, all manner of bad things will happen. I have a clue which is that the label on my toroid does explicitly say "0-18v (black - white)" and ditto for the red - yellow. Is that enough information to go ahead and connect em up or is there anything I can measure with a multimeter to be sure?

Thanks.
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post #2 of 12
7/24/11 at 6:39am

I would assume the black and red wires are for the ground marking on the terminal block, and attach the others to the wavey one.

 

Double check to see if the windings are shorted before you fire it up.

 

Good luck.

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post #3 of 12
7/24/11 at 7:02am
[=http://www.diyaudio.com/forums/parts/75236-how-determine-phase-transformer-secondaries.html][/]

http://www.diyaudio.com/forums/parts/75236-how-determine-phase-transformer-secondaries.html

First you must fuse the primary with the appropriate size and time fuse.

Never ever automatically assume that the color code or voltage rating is correct.

Secure all wires so that they have no chance of flying around and either touching you, or shorting against each other.

Normally the 0v could be used to indicate phase.

EDIT: could not get the link to work so just pasted the addy below it.
Edited by digger945 - 7/24/11 at 7:05am
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post #4 of 12
7/24/11 at 7:08am

Like digger said definitely use a fuse. Also you can test the secondary voltages out on the bench. Get a screw terminal block something like this: http://www.radioshack.com/product/index.jsp?productId=2103983. Screw the secondary wires down to that. Then hook the fused AC mains up to the primaries and measure the secondaries with your meter on ac volts mode to make sure they are outputting what you expect. They will likely be a bit higher than rated since the transformer is unloaded.

 

You can also make sure that the secondaries are in phase by following the procedure in digger's link.


Edited by bcg27 - 7/24/11 at 7:11am
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post #5 of 12
7/24/11 at 8:17am
Thread Starter 
Red to yellow and black to white both read as shorts. Does that give me any new information to go on?
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post #6 of 12
7/24/11 at 9:03am

Power up the transformer on the bench safely like those guys said above, and check for the correct voltage rating. Make sure the primaries aren't shorted with any secondaries before you do so. I like to use them fancy clampy multimeter tip things.

 

If it checks out fine, wire everything in and fire that bad boy up.

 

The red-yellow and black-white pairs showing as shorts(continuity)/low ohms mean that the secondaries are correctly labelled in terms of colour, but don't forget to check for voltage.

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post #7 of 12
7/24/11 at 9:27am
Thread Starter 
Excellent, she fired up first time! A nice, stable 15.06v on both rails. Thanks for the help.
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post #8 of 12
7/24/11 at 9:35am

Congrat. What's it for?

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post #9 of 12
7/24/11 at 10:14am
Thread Starter 
My pride and joy, 9 months in the making. It's a balanced Dynalo with Sigma22 and 25 power supplies. I haven't done any DIY electronics since school days so it's something of a learning experience!

Photo%2024-07-2011%2018%2005%2038.jpeg
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post #10 of 12
7/24/11 at 10:48am

Very classy.

I'm a sucker for black and red.

Let us know when and where you post more pics. 

Enjoy.

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post #11 of 12
7/24/11 at 12:03pm

Congrats on the successful power up! It looks great and I'm sure it sounds awesome as well. One aesthetic suggestion I would make is to replace the screws on the XLR outputs with socket cap screws. They look much classier IMO.

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post #12 of 12
7/24/11 at 12:40pm
Thread Starter 
Thanks for all the comments. The screws are indeed temporary, I have a few black anodised ones around here somewhere that should look much classier. cool.gif
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