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[Amps] Alpha 77D anode choke swap?

To: "" <>
Subject: [Amps] Alpha 77D anode choke swap?
From: Rob Atkinson <>
Date: Tue, 24 Apr 2018 12:32:47 -0500
List-post: <>
##  You are not after XL.  You are after Z..and there is a big difference.

No pure resistive component to the imaginary number.  Anything else?

## The 50 uh plate choke on the hb  YC-156 amp  is   wound with  20 gauge magnet

It can handle more current.   That doesn't reduce RF voltage to the
power supply.

## Bypassed at the base with a 4700 pf  @ 10 kv disc ceramic capacitor.  Also a
1500 pf
@  15 KV   HEC  doorknob cap.  The  4700 pf cap  does a better bypassing job on
the lower freqs.
The  1500 pf  doorknob does a   better bypassing job on the higher freqs.

If they are paralleled you have 6200 pF.  I don't have time to do the
math but I would still want more inductance.  That much capacitance
might be okay for a linear RF amplifier though.

I find your comment about the disc caps being "better," curious.  With
ceramic capacitors, "better" relative to frequency usually means lower
frequency current rating, and higher current rating means lower or no
value drift.  Disc ceramics don't usually do well on lower
frequencies, especially 160 m.  It makes much more sense, if you need
6200 pF to get that job done with one or more doorknobs rated for a
few amps at 1000 kc.

##   HV filter in the 6700 vdc supply consist of  4 x 47 uf @  4.5 kv oil
filled caps in series parallel.

That's all you need.  Get rid of the electrolytics.  Too much filter
capacitance and stored energy.  Oil much more reliable.

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