[AMRadio] Charcoal Briquettes and High Voltage Power Supplies


bcarling at cfl.rr.com bcarling at cfl.rr.com
Sun Oct 30 19:37:08 EST 2005


I bet most carbon composition resistors will withstand 600V so long 
as you use them within their power ratings. The larger 1 Watt and 2 
Watt jobs tend to also have a thicker insulation on 'em...

Of course I would never try to use a 1/4 Watt or 1/8 watt (or less)
on a high voltage circuit.

On 30 Oct 2005 at 14:02, Mike Dorworth,K4XM wrote:

> 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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