Please help me determine if something's wrong with my transformer

[warpie]

I was a bit embarrassed to ask but it'll help me not to go bananas....

Carnhil line out Tx : 1+1:1.7+1.7

That is:      1*------    -------*5
                            |  |
                            |  |
                  2-------    --------6

                  4*------  -------*7
                            |  |
                            |  |
                  3-------    --------8

All I want to do is an unbalanced-to-balanced conversion in 200-to-600 configuration. So, I connect both primaries and secondaries in
series and I use 1 for my unbalanced signal, 3 for ground, 5 for Hi and 8 for Low.

Now the problem is that the resulting balanced output is not symmetrical. High (5) has smaller level than Low (8).

If I connect only 4 and 3 and leave unconnected 1 and 2, the output is fine (symmetrical).
If I connect only 1 and 2 and leave unconnected 4 and 3, the output is asymetrical.
In both examples the secondaries are in series.

Am I doing something terribly wrong? The transformer is brand new so I hope it's something from my end.

Thanks
w.

 

[CJ]

6 and 7 are tied together?

measure ac volts from 5 to 8,

take the clip off the ground lead and hook it to pin 8.

make sure your output jack is floating if using 1/4 inch

1/4 ich for balanced out?

it happens sometimes in the diy world,

 

[warpie]

6 and 7 are tied together.

I first noticed this in the unit but now I've been testing the transformer on its own (with a signal generator and a 2-channel scope)

The set up is: 

SigGen's +/- to 1&3  (2&4 tied together) ---> Scope CH1 at 5 and Scope CH2 at 8, (6&7 tied together).
Scope's CH1 & CH2 ground is connected to SigGen's (-) (i.e to 3).

 

[Samuel Groner]

Now the problem is that the resulting balanced output is not symmetrical.

With the high Z input of your scope, even minuscule capacitive stray/load differences will easily unbalance the transformer output. Fortunately symmetrical output is, in most cases, not necessary (common-mode rejection does not rely on this). Otherwise ground the center tap.

Samuel

 

[Samuel Groner]

PS: The interwinding C is probably enough to explain the output unbalance--you'd need to drive it with a symmetrical input signal (as I understand this is not the case).

Samuel

 

[PRR]

> High (5) has smaller level than Low (8).

Load with two 300 (330) ohms resistors to ground (balanced 600 ohm load).

Are the outputs now equal? If so, it only was unequal because of the small capacitances Samuel mentioned.

Another test. Since it is full-floating, you can ground 5 and measure 8, ground 8 and measure 5. Are these equal? (If stray C is large, this will still show inequality at high frequency.)

 

[warpie]

Thank you gents! I'll try your suggestions and will report back