Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: labb on July 04, 2013, 07:13:12 pm
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Concerning the 470 ohm screen resistors, the 4.7K and 10K power supply resistors..These four resistors can see as much as 450 vdc. Most of the resistors I have used are only rated for 350 vdc. Think these should be rated for 500 vdc. I have not been able to find a 10K rated for 450 vdc. Guess I could use two 5K in series but rather not. What have you folks been using for these resistors. ? (I'm asking about the voltage rating, not the power rating)
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> only rated for 350 vdc
End-to-end.
The resistors you cite have like 450V on one end and 400V the other end.... only 50V across them.
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> only rated for 350 vdc
End-to-end.
The resistors you cite have like 450V on one end and 400V the other end.... only 50V across them.
+100 , this is 400 V under the max rating
Myself I never read these voltage spec on any resistor catalog . Where do you find or read that ?
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Maybe I didn't state the question clearly..This is what I am concerned with:
"Voltage rating : as with wire insulation, make sure this will handle the voltages you care about. In most resistors, you only care about the voltage drop across the resistor, but if the resistor is up against, or can possibly touch, another conductor (such as a ground lug!) or another resistor, you have to worry about the maximum potential between the resistor and the other conductor or resistor. "
A resistor's voltage rating is generally stated on that resistor's data sheet.
From the answers I would gather that you guys don't consider the voltage rating of a resistor. Mostly if the layout is good then it doesn't have to be considered. I have a very restricted layout where some resistors will be against each others. looks like my best option would be to change the layout.
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labb, this make sense ,
I look on Ohmithe resistor link and found some spec ; I look at first resistor I see.
Test OX OY
Max Working Voltage 300V 400V
Dielectric Strength 500V 700V
Max Overload Voltage 600V 800V
Max Pulse Voltage1 14KV 20KV
Pulse Tolerance, 100 pulses
Thanks
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Yes, stratele52 found what your looking for, dielectric strength and it's rating is listed on the R spec sheets, as he just posted.
Just like on the insulation of a wire. They can also be found on spec sheets for coupling caps.
I can't think of a reason why any R or C would ever have a dielectric rating that would be less than it's max working voltage. Well except for 1 of those wire wound tubular adjustable R's. :think1:
Brad :icon_biggrin:
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> I can't think of a reason why any R or C would ever have a dielectric rating that would be less than it's max working voltage.
Just what Labb is doing. The resistors feel 50V end-to-end, but rub against other parts 400V different.
Aside from sparks jumping through, rubbing resistors will be way down on power dissapation (need good air around them).
Build looser, or be brave (and ready to open a window!).