Beginner's Question : Identifying wires on a unknown transformer

[DJDestiny]

Yes i have one unknown toroid and one 50VA 12V but unknown wiring , here :

[AndrewT]

Almost 1.9MB of out of focus pics downloaded from a slow remote server.
Why does the Forum allow this?

[DJDestiny]

Originally Posted by AndrewT

Almost 1.9MB of out of focus pics downloaded from a slow remote server.
Why does the Forum allow this?

Tinypic IS not a remote server .
It's operated by photobucket .

[Spiny]

Originally Posted by DJDestiny

Tinypic IS not a remote server .
It's operated by photobucket .

Remote server is any server that is not DIYAudio, Andrew is right.
You can upload images to DIY Audio, the system will thumbnail your images preventing the long slow load of oversize images and allowing folks to click on any of interest.
Edit, see they have been scaled down to visible sizes now. Unfortunately the photos are not informative.


As to the original question -

In general with transformers, identify the pairs of leads and label (A-A B-B C-C-C etc) Usually the high resistance pair are the power input (Line).
now take an AC feed, a 12v AC transformer is handy for this and connect to the supposed line pair, measure voltages on the other pairs / tapped windings. This will give the ratio of voltages between the windings.
From this you can work out the transformer windings.

Word of warning, do not connect the 12V AC to a low resistance winding as this could provide 2 or more times the line voltage on the high resistance pair if its a low voltage transformer. Possibly damaging it

[DJDestiny]

Well 240 to 12-0-12
just not sure how to connect the primary to fuse / switch mains
what fuse and bridge diode should i use? It's a 50VA tranny .
Why would the toroid have 4 wires?

[Spiny]

connect to the mains via a switch and a fuse (0.5 to 1 amp will do, this is a safety fuse in case the wires come adrift) on the secondary side (the 12 0 12) you need to fuse for 4 amps with a slow blow type, connect the bridge across the 12v wires, the centre tap is the ground, will give + and - 17 volt approx.

4 wires only should be 2 for the primary and 2 for the secondary, check with meter

[DJDestiny]

Originally Posted by Spiny

connect to the mains via a switch and a fuse (0.5 to 1 amp will do, this is a safety fuse in case the wires come adrift) on the secondary side (the 12 0 12) you need to fuse for 4 amps with a slow blow type, connect the bridge across the 12v wires, the centre tap is the ground, will give + and - 17 volt approx.

4 wires only should be 2 for the primary and 2 for the secondary, check with meter

4 secondary because of 40/40 volts.
Not sure what the rating is though, as for info it says cree there.
Thw primary ( two pink ) has no continuity or resistance :<
on the 12-0-12 is -12v black 0v yellow is it?

[Spiny]

Originally Posted by DJDestiny

4 secondary because of 40/40 volts.
Not sure what the rating is though, as for info it says cree there.
Thw primary ( two pink ) has no continuity or resistance :<
on the 12-0-12 is -12v black 0v yellow is it?

Open circuit primary if no continuity, thats junk

as to the other, A transformer is AC there is no + or - until its rectified, the wires are 12Vac 0AC 12Vac
see the uploaded image for suitable circuits, ones give a single output, the other + and - both have the same total wattage available (50VA in your case)

hmm seem to have messed up the image should be +/- 16V not +*16v

[DJDestiny]

Originally Posted by Spiny

Open circuit primary if no continuity, thats junk

as to the other, A transformer is AC there is no + or - until its rectified, the wires are 12Vac 0AC 12Vac
see the uploaded image for suitable circuits, ones give a single output, the other + and - both have the same total wattage available (50VA in your case)

hmm seem to have messed up the image should be +/- 16V not +*16v

I forgot we're talking AC here , stupid me .
Yeah , it has a center tap on both sides .
Great , now i have 2 x 2200uf 35V caps , buying 7809 and 7909 soon .
Argh , lately my projects have been adding up , the number of projects on my table is straight off hitting 7 , and i still have secondary school to go to !
( Oh , i'm still 17 , )