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Replacement of tube amplifier kit filter choke

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luiHS:
Hi.
I have a tube amp kit that I bought many years ago, I think at least 30 years ago, I'm going to see if I can assemble it.

The fact is that I am missing a piece, specifically Z1, which I think is a double choke to filter 50Hz AC. Since it's something so old and I suppose it was a custom made part, I can't find the original replacement. What strikes me is that the two filter chokes are in a single encapsulation.

In the list of materials in the magazine neither the value of the choke nor the current is indicated, only the TA30 reference. I have been looking at other schematics in a book that I have and they usually use 10H chokes but they are usually to supply a lot of current because they also feed the final power tubes. In this kit the choke is quite small and only feeds the low power tubes of the previous stages (ECC82, ECC83), not the final tubes (KT88).

In short, what would be the appropriate value to find a replacement for this filter choke?, value of the inductance and current in mA. And if anyone knows if there are double chokes.

Each channel installs 1 x ECC83 and 3 x ECC82 tubes, and 2 x KT88 for the final power stage. 

TimFox:
I believe it is actually a double choke:  1/2 of it is a series impedance that drives filter capacitor (C26 in series with C27) to reduce the power supply ripple to the voltage amplifier stages.
The other half connects the HV supply to a similar capacitor on the other channel.
Since the current draw of the voltage amplifiers is much less than that of the output stage, you may want more than 10 H in each of two isolated chokes (if you have space to mount them) with sufficient insulation voltage (> 450V).
Those capacitors are not specified on the drawing:  what is the capacitive reactance of the series combination at 100 Hz?
The choke inductive reactance should be substantially greater than that (to avoid resonance at 100 Hz).

luiHS:

--- Quote from: TimFox on June 04, 2023, 09:53:50 pm ---I believe it is actually a double choke:  1/2 of it is a series impedance that drives filter capacitor (C26 in series with C27) to reduce the power supply ripple to the voltage amplifier stages.

Those capacitors are not specified on the drawing:  what is the capacitive reactance of the series combination at 100 Hz?

--- End quote ---


C26 and C27 are 100uF 400volt
R49 and R50 are 100K 2W

TimFox:
50 uF at 100 Hz is -j 32\$\Omega\$
10 H at 100 Hz is +j 6300\$\Omega\$, which should be plenty for this application.

luiHS:

--- Quote from: TimFox on June 04, 2023, 10:37:17 pm ---50 uF at 100 Hz is -j 32\$\Omega\$
10 H at 100 Hz is +j 6300\$\Omega\$, which should be plenty for this application.

--- End quote ---

The filter chokes do not indicate their value in Henries for the inductance, and in mA for the current they support ??
The choke would then be 10 Henries. But how many mA?

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