Help with output transformer wiring

[Joe6v6]

Im using the transformers from the attached schematic for a 4xEL34 build, I am unfamilure with the way this output transformer is wired. What is the orange (ORN) wire at the top of the output side? Is it a 16 ohm tap that is used for some sort of negative feedback or something else? What should I do with it in the same type setup as a 100 watt marshall?   Thanks  : Joe

[92Volts]

It is used for feedback, but doesn't drive a speaker. There's no way to know if it can supply enough current to drive a 16 ohm speaker (probably not) or if the level is equal to a 16 ohm speaker tap. I would leave it unconnected and use the red (8 ohm) or brown (4 ohm) wires for feedback.

There are still 2 wires shown without the colors labeled-- the common/ground on the secondary side and the center tap on the primary/tube side. You can check with an ohmmeter which winding an unknown wire is part of, and they're hopefully bundled with or located near the other primary/secondary wires.

[2deaf]

What is the orange (ORN) wire at the top of the output side? Is it a 16 ohm tap that is used for some sort of negative feedback or something else?

What are the turns ratios for this transformer?

[Joe6v6]

It is used for feedback, but doesn't drive a speaker. There's no way to know if it can supply enough current to drive a 16 ohm speaker (probably not) or if the level is equal to a 16 ohm speaker tap. I would leave it unconnected and use the red (8 ohm) or brown (4 ohm) wires for feedback

This is what I was thinking, best to just leave it disconnected. I can live with just 4 & 8 ohm.

There are still 2 wires shown without the colors labeled-- the common/ground on the secondary side and the center tap on the primary/tube side.

Ive got this part figured out, Black on the secondary & red & white on the primary, I wont be using the ultraliner taps.

What are the turns ratios for this transformer?

Is there a way to determine this? I have no idea.


         Thanks for the help : Joe

[2deaf]

Is there a way to determine this? I have no idea.

You basically put an AC signal into one side and see what comes out the other side.  I don't know what equipment you are armed with, but the tests can apparently be done with a 6.3V AC signal and a voltmeter.

I'm betting that the mystery tap is 16r just like a zillion other transformers. 

Now that you mentioned UL, I think I know how the switching should go for triode/UL modes.  The drawing has the switch drawn wrong. 

[DummyLoad]

also missing is the Base drive for 2N4401 for channel switch indicator.


how it should be wired for UL switching - see attached.


--pete

[2deaf]

Attached is what I thought they were trying for:

[92Volts]

You basically put an AC signal into one side and see what comes out the other side.  I don't know what equipment you are armed with, but the tests can apparently be done with a 6.3V AC signal and a voltmeter.

Yes-- keep in mind, the winding (voltage) ratio is the square root of the impedance ratio. So a 16-ohm tap outputs 2x greater voltage as an 4-ohm tap. If you apply 6.3v AC to a 4 ohm tap you'd expect to see 12.6v from a 16 ohm tap.

This produces a larger voltage on the primary side, remember this for safety and to not kill the OPT.

The voltage ratio between 2000 and 4 ohms is sqrt(2000/4)=22.4, so 6.3v is scaled up to 140v or so on the primary of a 2k transformer. That's pretty normal/safe for a tube amp. Do NOT apply 120v to the 4 ohm tap, as this "wants" to create thousands of volts on the primary but will likely destroy things first.

Now that you mentioned UL, I think I know how the switching should go for triode/UL modes.  The drawing has the switch drawn wrong.

It's definitely wrong, it shorts the UL taps to the plates as-shown. The right wires are there, but the switches are "rotated".

[Joe6v6]

I applied 6.3v to the primary side - center tap & blue wire , on the secondary side there is .4v brown, .6v red , .85v orange. So with the orange wire being a little more than twice the brown (4ohm tap) it makes sense that this is a 16 ohm tap, correct?

[2deaf]

The results are consistent with a 2000 Ohm primary and a 4, 8, 16r secondary.