Changing ratio of esl-transformer

[Quongelvis]

Hi

i am not new to diyaudio but this is my first post in 6 Years :-)

I want to change the ratio of my esl-transformers from 1:150 to 1:75,
but i'm not sure how to do. The red and black wires are the primary side,
the blue cable is +, the yellow - of the secondary.
Whats irritating me is the yellow cable in the middle of the secondary side.

Can someone tell me what i have to do?

thanks
Carsten

[bentl]

Hi, I doubt that you can change the ratio of this transformer.

It seems to be 2 X 1:75 transformers "doubled" with the yellow wire as the center tap where the polarizing voltage ground/negative is attached.

If you want to reduce it to half ratio you will have to remove halve of the secondary windings on both coils.

or is there 3 wires on the secondary of both coils? your picture does not show the secondary very well

Regards,
Bent

Why do you want to do this?

[Quongelvis]

Hi Bent,

thanks for your reply.

The secondary side only has the yellow and blue cable to the panels and the grounding cable in the middle which also connects the 2 windings. There are no connectors in the middle of each winding.

Carsten

[bentl]

Then you can't use only half of the transformer.

I still dont know why you want to do this - if you explain there may be other ways to solve your problem.

Regards
Bent

[Calvin]

Hi,

not so quick young Padawan
There might be the possibility to change to 1:75 in the following case.
If each of the two legs of the transformer is a true 1:75 and the primaries have been connected in parallel the output would yield the 1:150 ratio.
You may connect the primaries in series instead to get 2:150, hence 1:75.
May I ask why You want too change from 1:150 to 1:75??

jauu
Calvin

[Quongelvis]

Hi,

the Transformer is in parralel on primary and secondary side.
This is the sheme, black points are soldering points, some are cold ones :-))
My reason for the change is that for frquencies higher ~100Hz i've been changing segmentation, surface is ~3 times more, so even the load for the amp should be, i think. I did this because i like beaming speakers much more. My switching amp can handle this very good, but i have a KT88 Tube amp which i want to give a chance after repair. Maybe this can end up in biamping on 2 transformers with the tube and line-highpass for the fullrange-panel and the switching amp for bass-panel, but better one step after the other :-)

Calvin, as far i unterstood i have to connect the -pole of signal and the -pole of hv to the left side of the left primary and cut the wire going from the right side of right primary to the left side of left primary. Is that ok?

thanks

Carsten

[Calvin]

Hi,

primary side is the low-voltage amplifier side, secondary the HV-ESL side. Your diagram looks faulty.
This is a correct schematic.


jauu
Calvin

ps: Somehow I´m not able any more to include thumbnails from imageshack that open up on full size by clicking. Just thumbnail size or just fullsize images. What´s the solution?

[Quongelvis]

hi Calvin,

thanks for the Sheme
i have been looking again and adapted what i see to your sheme.
I don't know if the changed palarity of P1 andthe direct connection between P1- to P2makes a Difference. If you think that function is different i better would not change anything now.

Carsten

[alexberg]

Originally Posted by Calvin

Hi,

primary side is the low-voltage amplifier side, secondary the HV-ESL side. Your diagram looks faulty.
This is a correct schematic.


jauu
Calvin

ps: Somehow I´m not able any more to include thumbnails from imageshack that open up on full size by clicking. Just thumbnail size or just fullsize images. What´s the solution?

Well, I would of wound 10 turn test coil over existing windings, then connect primaries counter series (end to end), apply voltage to the test coil and check the voltage at the beginnings. Basically, you substact voltages on primaries induced by test coil.
In case the primaries are equal no voltage will appear between two beginnings. If so you can safely connect them in a parallel per Calvin's drawing. If not you will get "shorted turn" rendering your trafo more or less useless.
Alex

[Calvin]

Hi,

in my diagram the upper circuit has the primary sides connected in parallel and the lower circuit has them connected in series. What You have to keep in mind is the direction of the magnetic flux. With the shown diagram the flux is in the same direction. The real worlds tranny the direction of flux in the left leg is opposite to that of the right leg. So You need to toggle one of the primary windings if the connections of the primaries as well as the connections of the secondaries shall be on same sides of the winding.
The attached schematics shows the different connection.

The red arrows show the direction of magnetic flux.
The difference between A) and C) on one side and B) and D) on the other is just the toggled second leg of the windings.

At the moment You should find B), what You want is D)

jauu
Calvin