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Resistor voltage ratings
Resistor voltage ratings
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Old 7th March 2018, 02:56 PM   #11
leadbelly is offline leadbelly  Canada
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I started the same thread almost 10 years ago.
Importance of resistor working voltage spec?

2 things I learned from that thread: a lot of DIY builders ignore resistor voltage rating, and the DIY designs where you nothing lower than 1W rating on resistors are because the builder/designer does not ignore the voltage rating.
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Old 7th March 2018, 03:45 PM   #12
hpeter is offline hpeter  Slovakia
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Originally Posted by leadbelly View Post
2 things I learned from that thread: a lot of DIY builders ignore resistor voltage rating,
if you work whole life with C and semiconductors, you will never cross the 300-500V max rating
but with tubes.. yikes
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Old 8th March 2018, 12:25 AM   #13
Marksd is offline Marksd  United States
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df96...One thing I did with my tube equipment was add a thermistor in the AC line to keep the inrush voltage lower at cold turn on. Where I live my AC line voltage caries from 114.5 VAC to 122 VAC. I think most of this spread is due to A/C loading and other such demands in the summer and furnaces in the winter. I also set my bias voltages so that my ST70 amps steady state at about 40MA per tube instead of 50MA. This way I know whether the AC line is high or low I will always be under the 50MA plate current.
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Old 11th March 2018, 03:59 AM   #14
PRR is online now PRR  United States
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Originally Posted by BillWojo View Post
...so it's not the voltage it "see's" but the voltage it drops...
Let's lash-together an iPod, your Dyna, and a speaker. Oh, and an isolated battery inverter supply. Get a well-insulated stick (Do Not Try This At Home!!) and hook it onto the 13,000V wire at the end of your street. The one the birds sit on. Everything is fine.

Inside the Dyna, most resistors have one foot on a 250V line and the other foot on the head of a 12AX7 dropping 150v. So it only "feels" 100V.

Violating the 350V rating is usually not quickly fatal. 1,000V on a 1/8W part, yes, a little surge may start an arc and burn it up. 500V on a 1/2W part sits quietly but drifts in value over the years. Truly high-voltage guitar preamps often use 2W-rated parts for plate resistors for the better voltage drift, even when the happy-amp dissipation is under 1/4W.
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