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Novice question - determining resistor power rating requirements
Posted: Thu 12/02/21 8:49 am
by cstenger5
This question is both practical for me and something I'd like to understand in general.
Practical: I have some decent 1/2 watt resistors and want to know if they're underrated for the circuit, since I typically use 1 watt where these would be.
General: What are the general rules or tendencies for power ratings for resistors in an amp circuit?
Re: Novice question - determining resistor power rating requirements
Posted: Thu 12/02/21 9:56 am
by cstenger5
Something I found:
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Here's a quick 'n dirty guide for 5W-25W amps:
First and second power supply dropping/filter resistors - 5W
All other dropping/filter resistors - 3W
Power tube cathode - 5W if separate, or 10W if shared by more than one tube.
Power tube screen grid - 1W
Everything else - 1/2W
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Re: Novice question - determining resistor power rating requirements
Posted: Thu 12/02/21 11:56 am
by JMPGuitars
cstenger5 wrote: ↑Thu 12/02/21 9:56 am
Something I found:
---------------------------
Here's a quick 'n dirty guide for 5W-25W amps:
First and second power supply dropping/filter resistors - 5W
All other dropping/filter resistors - 3W
Power tube cathode - 5W if separate, or 10W if shared by more than one tube.
Power tube screen grid - 1W
Everything else - 1/2W
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That guide is typical, but personally I use 1W wherever possible for the "everything else" stuff. Sometimes I can only get resistors in 1/2W, and it really doesn't matter for those spots because it would be in a low voltage/low current section. That's what you pay attention to- a lot of 1/2W have lower voltage handling, like 250V or so. The 1W CMF resistors I use can all handle at least 500V, so I don't have to pay too much attention in these circuits.
Re: Novice question - determining resistor power rating requirements
Posted: Thu 12/02/21 12:49 pm
by cstenger5
Thanks Josh!