Negative voltage from Center tapped vs Dual transformer

Thread Starter

kriksis

Joined Feb 23, 2016
27
Hi all,

Yesterday hooked it up to find the secondaries. As a surprise came fact, that pin 6 had red dot under it. Made me think, it was the common. Seems, that someone in factory had mixed the pins I guess, since after my results the common is pin 5. Results are somewhat satisfying. Pins 5 to 4 and 5 to 6 have ~22vac.
5 to 3 and 5 to 7 have ~40vac.
I guess this means it's center tapped after all. Seems rather strange, that different voltage secondaries have same tap. (or is it common practice to have it like that?)

These voltages are all I need. But I wouldn't be me if I didn't bother some of you with my questions. :D

Three last pins are rather strange -
pins 8 to 9 have ~13vac.
Pins 9 to 10 have ~11vac.
Pins 8 to 10 reads total of ~25vac.
(Remeasured 4 times. Human error unlikely but possible)
Thing, that I don't understand is, if pin 9 is CT for that winding, why aren't it in center?
 

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Last edited:

Dodgydave

Joined Jun 22, 2012
11,395
(Why isn't it in the centre)
It doesn't have to physically be in the centre of the transformer, it can be brought out anywhere, as for the 25Vac reading pins 8-9-10, it could be designed for that, or its within its tolerance level.

Try measuring the resistance of the windings to see if they are all connected or separate windings.
 

Thread Starter

kriksis

Joined Feb 23, 2016
27
It doesn't have to physically be in the centre of the transformer, it can be brought out anywhere
I didn't mean why isn't it in physical center. :) I meant, the difference between the voltages and why the tap isn't splitting the voltages in half.

Well, the resistance measurements showed that pins 8, 9 and 10 have continuity and are separate from the rest pins. If this could be a design feature, then no further questions regarding this.
 
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