Sowter TVC mystery

discussion of magnetic volume control design for both line and speaker levels.

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DowdyLama
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Sowter TVC mystery

Post by DowdyLama »

I am rebuilding a linestage for a customer utilizing a Sowter TVC at the input - someone else did all of the original wiring; I am simply replacing the original 6AH4 with a filamentary-bised 71A.
In tracking down some minor hum, I discovered that the ground on the TVC secondaries is ungrounded...which makes me wonder: how is it biasing?
What am I missing?
dave slagle
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Post by dave slagle »

more importantly, with only one wire of the secondary hooked up how is signal transferring?

dave
JeffreyJ
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the mystery...

Post by JeffreyJ »

I talked to jimmy on the phone about this one... so, just to make sure we were crazy, I had him measure grid to ground on the 71a.. we measured open circuit... even with the volume (tvc) on the first "click"... but he has measured the bias of the tube and all was fine.. it makes music.. someone, PLEASE explain this one to me...

Peace,
Me
DowdyLama
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Post by DowdyLama »

I did ground the secondary (which eliminated that last bit of hum I was tracking down), but I still don't understand why it was working at all!
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