3 Legged Inductors

[istari knight]

Anyone seen one before ? I've got some old Mordaunt-Short Pageant II's & intend to upgrade every part of the crossovers but this inductor has me stumped

[IMGDEAD]https://i26.photobucket.com/albums/c129/istari_knight9/t0TC2nPh_zps4e76ee0c.jpg[/IMGDEAD]

I haven't measured it yet but I'm guessing it may be 2 in 1 or something like that ? I'll update with measurements later...

 

[mondogenerator]

ive seen similar but in power supplies. Id wager its centre tapped, or maybe offset centre tapped. You could likely do similar with 2 inductors of the right value. Either that or its making use of mutual inductance, but i think thats less likely with 3 wires (no electrical isolation)

 

[Zeta4]

I think it could be an autotransformer to adjust the treble level.

 

[mondogenerator]

I think it could be an autotransformer to adjust the treble level.

Or it could be that.

 

[istari knight]

Thanks for the input chaps but I think you were right with "offset center tapped."

I neglected to mention these speakers have 2 x SPDT switches in each crossover as can be seen here:

[IMGDEAD]https://i26.photobucket.com/albums/c129/istari_knight9/pagplate_zpsc6898426.jpg[/IMGDEAD]

The switch in the tweeter section adds an extra 4R7 resistor & the switch in the bass section changes the inductors tap from 1mh to 1.6mh.

I haven't got the skills to reflect this in a diagram so have done 2, the first with switches in flat position & the second with switches in cut position.

[IMGDEAD]https://i26.photobucket.com/albums/c129/istari_knight9/PageantIIFLAT_zpse35a8ebb.png[/IMGDEAD]

[IMGDEAD]https://i26.photobucket.com/albums/c129/istari_knight9/PageantIICUT_zpsf7b0dbb0.png[/IMGDEAD]

I do hope that makes sense!

 

[mondogenerator]

Thanks for the input chaps but I think you were right with "offset center tapped."

Well well well! Every so often I get something right What is a bit peculiar is C1 and C2 in series, would a single 2.2uF really have been a compromise too far?

 

[davidsrsb]

Using polarised parts back to back to save money?

 

[istari knight]

Using polarised parts back to back to save money?

All original caps were Elcap Non Polar "low loss" types.

It is rather odd, I had to double check that I hadn't got it wrong but that's how it is...

 

[mondogenerator]

maybe the extra series resistance of 2 5uf worked better than a single 2.5 or 2.2uF?

 

[Inductor]

Well well well! Every so often I get something right What is a bit peculiar is C1 and C2 in series, would a single 2.2uF really have been a compromise too far?

It's possible that it's a 3rd.order, like another member in another forum stated.
It then makes perfect sense for a ~3.5KHz crossover.
http://www.lencoheaven.net/forum/index.php?topic=12292.45

istari knight, doesn't the cable you are using very bad, or did you upgraded already?!
Use this type of cable (professional Speakon type) if nothing else. You can achieve a good improvement in total quality. It's not expensive (1x ten meter run can give you two cables), gauge/quality and it's adapted to all situations (black heavy PVC jacket or clear zip-cord jacket for audiophile applications). You don't need the bulky connectors, so, can save for later use or sell as parts.
http://www.radialeng.com/rcs/pdfs/radcat-speaker.pdf
Speakon Heavy Duty Speaker Leads : PA Speaker Cables : Maplin Electronics

 

[istari knight]

Thanks for the input Inductor

I think you may be right about the 3rd order filter at least that makes sense... I'll have another look at the PCB but its quite difficult to trace as the tracks are very erratic.

I'm afraid that's not my project on the Lenco forum. I simply used his crossover picture. I am using Van Damme 2.5mm cable

 

[istari knight]

Okay I have just looked with fresh eyes & Inductor is correct. I'll amend the schematics...

 

[mondogenerator]

well spotted Inductor That would explain the 2 capacitors where the choke should join between them in a T.

 

[istari knight]

Well It wont let me edit the previous picture's so I deleted them just in case someone in the future makes the mistake of using them. Here is the correct crossover:

[IMGDEAD]https://i26.photobucket.com/albums/c129/istari_knight9/PageantIIFLAT1_zps360d3118.png[/IMGDEAD]

[IMGDEAD]https://i26.photobucket.com/albums/c129/istari_knight9/PageantIICUT_zpsae257c1b.png[/IMGDEAD]