Heater Center Tap Question

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Good morning all,

 I’m just now completing the Dual Lite British, and upon ringing everything out my heater pins are ringing to ground. Is this because my center tap is referenced to ground? I looked at Slucky’s 6v6 plexi which seems to be running the same PT wire colors as mine, and it appears the green wire is the 6.3 CT. I’m doing the same thing, as seen in the photos. Have I got this correct, or am I missing something?

Thanks all,
NR

[PRR]

> it appears the green wire is the 6.3 CT.

Isn't that a direct connection?

[imgumby001]

> it appears the green wire is the 6.3 CT.

Isn't that a direct connection?

It just confused me when the heater pins rang to ground. I’ve never had that before. But looking through the builds I’ve got in front of me none have a heater CT, so I don’t have a comparison.

[kagliostro]

You are not obliged to connect the CT to ground

Usually better performance are reached using a pot as humdinger (pins of the pot connected to the extremities of the heater winding, wiper to ground or to a voltage divider for DC elevation, CT not connected)

Franco

p.s.: As humdinger use a 220R / 470R pot

[imgumby001]

You are not obliged to connect the CT to ground

Usually better performance are reached using a pot as humdinger (pins of the pot connected to the extremities of the heater winding, wiper to ground or to a voltage divider for DC elevation, CT not connected)

Franco

p.s.: As humdinger use a 220R / 470R pot

Thanks boss. Turns out, for the most part, I was just being a nervous Nellie. It’s fired up now and the voltages seem to be in or near spec. Unfortunately she’s a “hum bomb”! Signal is making it through, but it’s got an incredible amount of hum. My preamp volumes seem to be interacting with one another. I may have an issue with the switch I chose. Sounds pretty terrible actually. Boo hoo!! Makes me sad…

[kagliostro]

Apply usual things

Well twisted wires, path of the heater wires far from high gain stages, shielded wire on the path of the signal that is going to be highly elevated

Franco

p.s.: don't call me boss, I absolutely am not

[passaloutre]

The heater windings on the transformer have such low DC resistance, they should measure short to ground on many meters.

[kagliostro]

The heater windings on the transformer have such low DC resistance

Yes, to measure such a low resistance you require a special ohm meter

.... they should measure short to ground on many meters.

I don't agree, between the heater winding and ground (the transformer laminations if you prefer) you must measure an infinite resistance, if not you have a short

Franco

[passaloutre]

between the heater winding and ground (the transformer laminations if you prefer) you must measure an infinite resistance

Not if you have a grounded center tap

[kagliostro]

That will not be good practice, if you measure with the CT connected to ground, how do you can recognize if there is a short on the windings ?

Franco

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Well, the only thing I can add is it seems to be working great!! I have no voltage issues what so ever. I really do appreciate you guys and all your help!!!!

[passaloutre]

That will not be good practice, if you measure with the CT connected to ground, how do you can recognize if there is a short on the windings ?

Franco

Franco, I think we are both saying the same thing in different ways.

He said he has continuity between the heater windings and ground, and that the center tap is grounded.

I said the continuity is not an indication of a problem, as the DC resistance is very small.