Autotransformer Tap And Cheat Sheet Decoding (a long series of questions)

[JCBOHL]

Greeting Klipsch Heritage DIY Enthusiasts,

I am struggling to understand the conversion of a tap cheat to the actual physical wiring to and from the autotransformer. For example if replacing a Universal Transformers T7A with a 3636 or 3619-ET, how does one use the respective cheat sheets to wire a crossover to provide the equivalent level of attenuation. I understand the physics with the windings, etc. but I do not understand the wiring shorthand. I am comparing Klipsch original crossovers, Crites versions and ALK versions.

 

1. I believe that the "0" tap is the common or ground tap

 

2a. For instance the following 3619 tap settings includes "X" and I don't understand how this factors into a wiring diagram. I do not see "X" as a tap option.

2b. How does one then wire the input and output to produce a -9 dB attenuation? Input at the "0" tap and output at the "2" tap?

2c. How would one wire for a -9.8 dB attenuation where the table indicates X-3?

3619 tap settiings.pdf

 

3a. The Crites 3636 Autotransformer includes "X" and "Y" taps in the chart. Now how does this work?

3b. Additionally there are two columns for the taps and I'm not sure how this translates to the 3619 Autotransformer

3636 Autotransformer.pdf

 

Finally,

4a. The T7A (I cannot locate a chart for this at the moment) will provide attenuation of -10 dB with the input at 5, output at 2, and the ground at 0 taps. With the component I have, it has leads only at these "tap" setting and no tabs, so am I assume this is fixed in the level of attenuation? (I will not ask about using an inductor here)

4b. The lead at tap 2 actually is two leads and on is common with the 5 lead and the other with the 0 lead. Why is this? In the crossover network both of the tap 2 leads are connected to the same solder point.

 

5. One last question: Is there a coating on the wire leads coming from the T7A autotransformer? I had to apply a solvent and a mild abrasive to them to solder and produce an electrical connection.

 

Thanks for the assistance,

Jeffri B

 

 

 

[OO1]

5 hours ago, JCBOHL said:

 

I am struggling  replacing a Universal Transformers T7A with a 3636 

 .waste of time ,

[mboxler]

8 hours ago, JCBOHL said:

Thanks for the assistance,

Jeffri B

 

I'll start with the wiring and move on from there...

 

3619 -9.8db

 

 

 

3636 -10db

 

 

 

[Deang]

An autoformer is a tapped inductor. The Klipsch units provide working inductance in parallel with the driver to produce a 12dB/octave slope for the midrange. Depending on the unit, sometimes a coil is put in parallel with the autoformer to maintain this response. The inductance on the aftermarket units is too high and cannot produce this result. 

 

The wire is coated with enamel.

 

The 3619 is no longer available. The x tap is an additional output tap. 

The x and y taps on the 3636 are additional input taps. The x tap on the 3619 and 3636 do different things. You should probably contact the vendor with specific questions regarding their unit. 
 

3619-ET is similar to 3636 but with additional output taps. This unit is not for sale (as far as I know). 
 

I don’t know about Boxler, but I don’t have the energy for this anymore, lol. 

[mboxler]

16 hours ago, JCBOHL said:

 

4a. The T7A (I cannot locate a chart for this at the moment) will provide attenuation of -10 dB with the input at 5, output at 2, and the ground at 0 taps. With the component I have, it has leads only at these "tap" setting and no tabs, so am I assume this is fixed in the level of attenuation? (I will not ask about using an inductor here)

4b. The lead at tap 2 actually is two leads and on is common with the 5 lead and the other with the 0 lead. Why is this? In the crossover network both of the tap 2 leads are connected to the same solder point.

 

 

 

Tap names are confusing.  In the case of the 3636 and the 3916, X doesn't mark the same spot.

 

Here's the T7A.  The tap names are actually 0, 1, and 2 and the connections are in 0 - 2, out 0 - 1 (-10db).

 

 

 

 

Like Dean said, the T7A in an inductor, and one end is labeled 0, the other end is labeled 2.  Now imagine they are winding the inductor (call this end tap 0). When they reach 31.6% of the windings, they expose the wire and cut it.  The two ends of this cut wire are tap 1.  The rest of the wire is then directed back to the inductor and continues to be wound until 100% of the desired windings is reached (tap 2)

 

If the same tap names were used on a T2A (0, 1, and 2), the output voltage would be around -3db due to the winding ratios.

 

Mike

 

 

 

 

 

 

 

 

 

 

 

 

[JCBOHL]

Dean and Mike, Thanks for the primer. This is all much more clear. Universal Transformers Co. only provides the 3619-ET to B&K Sound (aka Crites), and Michael Crites has an agreement with Al Klappenberger to only use the 3619-ET to build crossovers. Alas, but I do understand. Hopefully I can get these Forte II back up and running soon.

 

Dean, Thanks for the clarification on the importance of the crossover slope.

 

Ah, so much to learn...Life was so much more simple with the AM radio in a '64 Dodge Dart listening to Buck Owens with Merlene in Bakersfield 😉

 

I'll see what I can find on the secondary market or how a 3636 can be adapted.

 

Cheers, Jeffri

[Deang]

What is wrong with your Forte II Networks?

[Deang]

@JCBOHL Where did you go? Can’t help without more information. 

[jbohlscheid]

Dean, I had to go to work. And for some reason my accounts and passwords got messed up.

The long story is...The original issue was a dead tweeter in one of my Forte ll speakers. The diaphragm looked good and I swapped with the other speaker and determined it was not related to the driver of diaphragm. Then I started poking around the crossover after the wiring looked good and I checked the continuity for shorts or breaks. As these speakers were build in 1989 I suspected one of the mylar capacitors my have failed. Thus I ordered a capacitor kit from B&K (great prices) and started building a new network, but not using the PC board. Comparing the speakers, the upgrade of capacitors, resistor and new inductor is noticeable. I reused the T7A autotransformer and the iron core inductor from the OEM crossover. Of course this got me thinking about the ALK system and giving that a shot. I did find a pair but one was in bad shape and the autotransformers were missing or crushed. I don't know the story behind this, I just came across them. Thus I decided to try to get them going and give them a shot. I am a novice DIYer and looking for challenges and good sound.

[deafyet]

I feel your pain JB, im trying to build a set of ALK /FORTE2 from scratch, and cant find a 3619 anywhere..

[winglet]

15 hours ago, deafyet said:

I feel your pain JB, im trying to build a set of ALK /FORTE2 from scratch, and cant find a 3619 anywhere..

What are you trying to accomplish that only a 3619 can do?

[deafyet]

I was just following the parts list, but will use a 3636 instead. What did you arrive at for a finished product?