Connected a transformer wrong, I think

I purchased a transformer ( Myrra 45065 http://www.farnell.com/datasheets/484324.pdf ) and I clearly did something wrong as it overheated in only a few seconds - I disconnected it as quickly as I could.

Now, I do have electronics experience, but mainly signal electronics and mains repair work. I bought this transformer because I wanted a dual 18V AC supply to connect to an old Soundcraft Spirit folio 122 mixer to see if it is working.

I connected the mains via veroboard to transformer pins 1 and 9, and then linked 4 and 6. I didn't attach anything to the apparent secondary winding, I just soldered 16,17,14,12 to the veroboard as I wanted to check the output. I didn't link the secondary winding.

I'm totally confused, but this is the first time I've dealt with a transformer so I prob made a stupid mistake. Any help greatly appreciated, thanks.

EDIT: I connected 240V to the apparent primary as I said earlier, not 110V.
 
Last edited:

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Your wiring is correct for the primary.

I would advise you power up with a bulb tester (search the forum for that :)) but its just a low wattage mains filament bulb in series with the live supply. It saves mishaps. Then confirm the transformer is working OK and the secondary voltages are correct (without them connected to anything).

That's your first step.
 
Your wiring is correct for the primary.

I would advise you power up with a bulb tester (search the forum for that :)) but its just a low wattage mains filament bulb in series with the live supply. It saves mishaps. Then confirm the transformer is working OK and the secondary voltages are correct (without them connected to anything).

That's your first step.

That's a relief, thanks for the help, I'll get to it.:)
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
I'm thinking rather hazily now... could the phase of one of the primaries been incorrect.

I just looked on a similar (similar as in package style) transformer I use and its wired as you stated. So could yours be different ? and one winding needs reversing. Use a bulb tester though as it will save any problems.

If the tranny heated up as quickly as you say then something was seriously amiss.
 
I'm thinking rather hazily now... could the phase of one of the primaries been incorrect.

I just looked on a similar (similar as in package style) transformer I use and its wired as you stated. So could yours be different ? and one winding needs reversing. Use a bulb tester though as it will save any problems.

If the tranny heated up as quickly as you say then something was seriously amiss.

The bulb tester seems like a good idea, I put a 15 Watt bulb in series and it lit brightly so it does look like I've got a problem.

On the case, it says the following;

115V (1-4)
115V (9-6)

I'm thinking you're right, although I'm new to this it would make more sense if it were (this would tie in more with the way I originally wired it);

115V (1-4)
115V (6-9)

So, looking at this, should i link 4 and 9, and apply 240V to 1 and 6?
 
You were right Mooly, I connected like I said in the last post and got a two steady 18.3V out the secondaries, the 15 Watt bulb was also dim.

The secondaries are;

18V (12-14)
18V (19-17)

I'm going to connect the mixer to 12 and 17 while linking 14 and 19 to get my common ground.
 

discrete

Member
2010-09-11 8:39 pm

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