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Re: [Amps] (1) bleeder resistors - suggestion to leave them out; (2) tho

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Subject: Re: [Amps] (1) bleeder resistors - suggestion to leave them out; (2) thoriated filaments in "drilled-by-Customs" tubes; (3) oxygen-free terminals
From: Gene May <>
Date: Thu, 1 Mar 2012 18:34:31 -0500
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(1) I think this would be a BAD idea.  Some time ago, I bought a bunch of 
electrolytic caps to be used in a 3 KV plate power supply.  Out of curiosity, I 
put some DC across them for a couple of hours and then tested their leakage 
resistance.  There was a BIG difference, well over a 20:1 ratio.  If they had 
been put in series without bleeder resistances low enough to "swamp" the 
leakages, the voltage drops across the least leaky in the power supply would 
have exceeded their ratings by a considerable amount.  Wishing to reduce wasted 
current, I considered putting bleeders across each that would be "tailored" to 
their leakage.  After further testing, I saw that they each "aged" at a 
different rate, so after a while, some were significantly leakier than others 
and the voltage drops across each began to diverge significantly, and I could 
not depend on the voltage drops staying under their ratings.  So much for that 
idea.  Use bleeders.
(2) These tubes appeared to have indirectly-heated cathodes.  Thorium is put on 
the surface of cathodes of tubes (like 3-500Z's and 4-400Z's, also on 
consumable electric welding rods) whose filaments are  the cathodes; it 
increases the filaments' electron emission significantly.  It would be without 
function on indirectly-heated tubes, and is very unlikely to be put on their 
(3) Some persons in the "golden ear" high fidelity fraternity claim to be able 
to hear differences between "plain ordinary" copper wire and "oxygen free high 
conductivity" copper wire.  No comment on that.  Assuming that there might be 
some advantage to such terminals (?!?!?!), I have, ah, further doubts about 
whether such a pristine condition would be maintained after one soldered 
something to them.  My guess is that the author of the ad for those glorious 
terminals hadn't the least idea of what he was talking about, and threw it in 
as hype.
Gene May

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