54C Baffle - Printable Version

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RE: 54C Baffle - Radioroslyn - 10-04-2023

I have a question being that I'm hobbyist and not a trained professional in the business.
What does #46 do but add 60cy hum to the dc output of the 35Z5? I've seen it in other sets
and never quite understood why it's there. I don't think Muntz wound have left it in.

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RE: 54C Baffle - Ron Ramirez - 10-04-2023

morzh Wrote:Better.

Much better.

I have three 54 chassis and two cabinets, and (finally) have the elusive metal back for one. So I may re-add the safety switch to my set in the near future.

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RE: 54C Baffle - Ron Ramirez - 10-04-2023

Terry, I added that cap simply because I've seen it used in many "All American Five" AC/DC circuits. I'm no engineer, nor do I play one on TV. I have no issues with hum in my modified 54C.

It appears they may have intended to act as a "snubber" in rectifier circuits, from the limited reading I just did on the subject. Mike (morzh) could explain it much better, I suspect.

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RE: 54C Baffle - morzh - 10-04-2023

Terry,

First I did not see Ron's post, but he is (according to my understanding) is correct. It is a sort of snubber. Of course your typical snubber is an RC, but a cap was used in this case. Perhaps due to high losses in tubes (as opposed to today's solid state diodes).

Notice that you mostly see it in AC/DC sets (my portable Telefunken I restored recently has the same) and not in AC-only sets (with transformers).
My explanation would be that in case of AC-only sets the spike of the current via the tube, when it starts charging the first filter cap, is much smaller than that in AC/DC sets, for the reason of it not being limited by anything in the AC/DC case, as the tube is connected straight to the AC line, whereas in the AC-only case the tube is serialized with the equivalent parasitic inductance of the transformer and the loss resistance of the windings, which would limit the spike of the initial inrush current when the tube starts charging the first filter cap.
That larger spike in AC/DC radios may produce noise. I doubt it will produce high voltages and lots of ringing as the impedance of the tube, coupled with very low wires' inductances, would prevent it. However I am sure the engineers heard or measured something they preferred to snub a bit.

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