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figuring out an unknown transfomer

post #1 of 9
12/26/09 at 11:23pm
Thread Starter 
So i inherited a huge transformer from an amp. the problem is i have no idea on how to ohm it out to find primaries and secondaries. It just has 5 wires coming out of it. I assume that means 1 set of secondaries with a center tap?
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post #2 of 9
12/27/09 at 2:58am
Quote:
Originally Posted by nightanole View Post
So i inherited a huge transformer from an amp. the problem is i have no idea on how to ohm it out to find primaries and secondaries. It just has 5 wires coming out of it. I assume that means 1 set of secondaries with a center tap?
That is most likely the case.

The thinner 2 wires will be your primary and measuring the resistance between the other 3 wires, whatever common wire measures the same resistance to the other two will be your center tap.

What colours and position are the wires? You may be able to tell just from them alone
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post #3 of 9
12/27/09 at 10:21am
Thread Starter 
everybody is 14 guage. colors are blue yellow orange red brown.
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post #4 of 9
1/3/10 at 7:33pm
Thread Starter 
ok i ohm'd it out.

brown-blue is 1 ohm
red-yellow is 3 ohms

orange to yellow or red is 1.5 ohms


now if i plug it into the wall it pops the breaker on the power strip

I setup a 12vac unit to feed it

with 12vac in, im getting 140vac out or dual 70vac if i use the center tap


what in the world would this be used on? It came out of a solid state 1000+watt amp from the early 80's. If this hold up then it would be putting out kvac when hooked up to the mains.
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post #5 of 9
1/3/10 at 7:51pm
Looks like you have the input and output reversed.
Does a center tap necessarily imply that it must be used as a secondary?
Also, is it possible that the transformer you have isn't a power transformer, but an impedance matching one?
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post #6 of 9
1/3/10 at 7:55pm
Quote:
Does a center tap necessarily imply that it must be used as a secondary?
No.
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post #7 of 9
1/3/10 at 8:52pm
Thread Starter 
what would a center tap on the primaries be good for? switching between 4 ohms and 8 ohms? Im not even sure how that would work with a center tap. with dual primaries you could switch from parallel to series.
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post #8 of 9
1/3/10 at 9:12pm
Thread Starter 
Well i wired it with center tap side as the primary and hooked a volt meter to brown/blue

wall to red-yellow = 11vac
wall to orange to red or yellow = 22vac

Now this thing weighs 11lbs
That should put it over 400va in my book (unless standard weight is diff then toroidal weight)

Now for some questions so i dont kill myself

1. Is it possible to wire the thing for 22vac out and use the whole transformer (not just half). Maybe runing hot to the center tap and neutral to both primaries...
2. is there any problems just using the center tap to one other primary wire to get the 22vac out if that is the only option?




Crap if this thing is just a single secondary then i cant use it for a gainclone...
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post #9 of 9
1/3/10 at 11:42pm
My first guess would be the center tapped primary is for 110/220 input.
To deliver 1000w it would have to be in the neighborhood of 1000VA. Say the PS DC is 24V, then that would need @41A to make 1000w. 14ga wire. Perhaps the amp nomenclature is a bit deceiving.

24V is pretty common for projects around here. You can certainly use it for something in the future, or sell it to fund you current project maybe. I hardly ever find a 24V trans in an old piece of junk. Lucky you
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