[Heathkit] Screen dropping resistors (was DX-100B on Phone - bad audio distortion /oscillation)

[lee]

Rick:

To this add the fact line voltage is now around 125 volts rather then 
110-115 volts and you have another 60 volts or so added to the transformers 
output.  Now the dropping resistor will be handling more then the 21.3 watts 
you calculated.

-----Original Message----- 
From: Rick Poole
Sent: Friday, December 16, 2011 12:02 AM
To: heathkit at mailman.qth.net
Subject: Re: [Heathkit] Screen dropping resistors (was DX-100B on Phone - 
bad audio distortion /oscillation)

At 12:54 AM 12/16/2011, lee wrote:

>>>>>
>If they have two 10 watt resistors in series and you have 11 watts
>through the chain of 2, you only have 5 1/2 watts through each
>resistor as each resistor is dropping the voltage by 1/2 the total
>amount.  In other words, two 10 watt resistors in series gives you
>one 20 watt resistor.
<<<<<

No, it's nominally 11 watts each.  Power dissipation is a total of
just a bit under 22 watts total through the chain of two... voltage
drops from about 840 (HV) to about 187 (screen voltage) for a
difference of 653, square that and divide by 20K and you get about
21.3 watts, divide by two is 10.66 watts per resistor.

Rick WA1RKT

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