Quote:
Originally Posted by Yamamaya42
any one will work, as long as they are of the same power rating.
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That is not always true and caution is suggested when using ordinary resistors in high-voltage circuits.
Resistor types have specific voltage limits for particular versions. Film and the spiral-cut metal film typically are not rated for much above 500 VDC, lest they arc over. Tube amplifiers often use the wrong kind and don't blow up, but this is not a ringing endorsement for exceeding the specifications by a factor of 100. Not sayin', just sayin'.
Only specialized resistors are suitable — safe and reliable — for operating in the tens of kiloVolt range. So either a resistor specifically rated for the desired voltage must be selected or it must be constructed using a string of smaller resistors since, given
n resistors, the voltage across each resistor is
1/n of the total.
To demonstrate the issue, I dug out some of Vishay's offerings. Any resistor manufacturer would, of course, be suitable.
This page lists all of the Vishary carbon-film resistors. Pick any of the ordinary, i.e. not high-voltage, flavors and look at the PDF specifications. The voltage rating show the resistor is typically rated to about 500 VDC to 600 VDC, sometimes into the low kiloVolts for pulse operation:
www.vishay.com/resistors-fixed/carbon-film/
And here is an example of the high-voltage equivalents good for many tens of kiloVolts:
www.vishay.com/resistors-fixed/high-voltage
So best to order the appropriate resistor and know that it won't blow up. As an aside, many regulatory authorities like UL or CE, won't certify equipment using strings of resistors because the potential for arc-over can be high without proper layout.