[AMRadio] Charcoal Briquettes and High Voltage Power Supplies


Mike Dorworth,K4XM k4xm at arczip.com
Sun Oct 30 14:02:18 EST 2005


Sure don't want to fight on Sunday..but..most circuits avoid dropping more
that 500 volts across any one resistor, An example is metering circuits
where 1 meg resistors are series to make the total so that no single
resistor drops too much. There can be 5000 volts on the string, just limit
each one to about 600 volts. Mike
----- Original Message ----- 
From: <bcarling at cfl.rr.com>
To: <glowbugs-list at piobaire.mines.uidaho.edu>; <amradio at mailman.qth.net>
Sent: Sunday, October 30, 2005 1:52 PM
Subject: [AMRadio] Charcoal Briquettes and High Voltage Power Supplies


> In defense of the common carbon composition resistor...
>
> On 30 Oct 2005 at 9:35, N2EY at aol.com wrote:
>
> > Carbon comps aren't the most stable resistors in the world, and if they
age unevenly you've got a problem. Worse, they usually have a max voltage
rating of only
> > a few hundred volts, so in many designs they're being overstressed.
>
> Er, not so - they are regularly used in commercial power supplies
> in the 1000V to 2000V DC range.
>
> Most amateur radio tube rigs used final HT of around 600 to 900V
> DC
> and they used carbon resistors too, so I'm not sure where you got
> that idea from, but it is erroneous.
>
> Many audio amplifiers and modulators use 400 to 800V or more.
> Often a lot more.  As far as I know they all used carbon resistors.
>
> If it still works after 10 years then I don't think it is fair to call
> this results of such a design "overstressed."
>
> (Runs and ducks for cover...)
>
>
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