Working voltage for MOX HV resistors

[ohohyodafarted]

I am in the process of rebuilding the entire HV cage of a 15" Westinghouse early color set. It was worked on and botched up real bad by a "would be" restorer. In fact the entire chassis was a complete mess.

Rebuilding the HV cage on this Westy involves the replacement of many MOX (metal oxide) high voltage resistors. MOX resistors are difficult to obtain in the specific values and wattage's that you need, because distributors do not stock them, and they are expensive. I found a good source in Switzerland. This is a link to their web site, and they have an online store. http://www.high-voltage-resistors.co...RoCPzMQAvD_BwE

A MOX resistor is the type that is made from a ceramic body, and has a "candy cane" metal oxide resistance stripe spiral around the ceramic body. On modern MOX resistors the body is coated in either a ceramic fired glaze, or epoxy coated. The higher quality MOX resistors have the fired ceramic glaze coating.

I thought some of you might be interested in a formula that will tell you how to determine the maximum working voltage of a high voltage MOX style resister.

Where E is the maximum working voltage of the resistor; and P is the power rating in watts of the resistor, and R is the resistance in ohms of the resistor.

E is equal to the SQUARE ROOT of (P*R)

As an example, if you have a 2 watt 80 megohm MOX resistor E (maximum working voltage) would be the square root of (2 * 80,000,000) = 12,649 volts.

So in a HV circuit a 2 watt 80 megohm MOX resistor will withstand up to 12,649 volts across it before it would break down . If you are going to exceed that calculated voltage drop, you would need to use a resistor with a greater power rating.

Hope this is of some value to somebody.