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Vertical 6EM7 Portable Amp
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Author:  mike567 [ 07 May 2020, 14:31 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

Might try swapping tubes with good amp and find out if you have a bad tube. (internal short)

Author:  john55 [ 07 May 2020, 15:58 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

mike567 wrote:
Might try swapping tubes with good amp and find out if you have a bad tube. (internal short)


Tried all the tube swapping combinations before coming on the forum Mike, but thanks for the input.

After Matt suggested out of phase transformer windings, I rewired the problem amp, reversing the series secondaries and lo and behold the amp's been behaving itself ever since. No pops or crackles and no hum. If someone could explain to me just how out of phase windings would take out the two resistors I would appreciate it. I assume it's an excess current problem, but I've searched and searched for information but can't find anything relevant.
Thanks to everyone for their replies to this post.

Author:  ILoveHiFi [ 08 May 2020, 00:09 ]
Post subject:  Re: Vertical 6EM7 Portable Amp

Out of phase transformers only effect the transformer temperature, the out of phase can cause the flux to get weried and it cooks the core of transformer.

You can check with the scope if your summing the negative part with the possittibe part by connect out of this phase, this will either cause a weird ac output or a reduced voltage.

At worst case ceneratios the Ground of 100Ohm can become a full return path for the 6.3V
So you get (6.3*6.3)/100 = 0.4W accross a 0.5W resistor.

If you swapped the windings arround and tube voltage heater did not change then it makes no sense, that the 100 ohms will cook if you reverse windings.
Your wasting your time if you want to find out the answer.
I don't want to know the answer even if any one knows it cause its wasting my time.

Theoritically out of phase windings will effect heater voltage, unless over voltage which it wasnt't otherwise the windings in or out phase will not effect the 100ohms.

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