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October 05, 2022, 05:27:04 AM

Author Topic: 220 ohm Resistor Wattage?  (Read 108 times)

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Offline greg788

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220 ohm Resistor Wattage?
« on: September 29, 2022, 08:46:59 PM »
What's the dissipation spec (wattage) of the eight 220 ohm carbon film resistors?

Online Paul Birkeland

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Re: 220 ohm Resistor Wattage?
« Reply #1 on: September 30, 2022, 05:25:02 AM »
The ones going from the power transformer to the chassis should be at least 1/4W parts.  The rest of them could carry a much lower power rating but often times resistors like this end up being more delicate than we would like for point to point wiring.
Paul "PB" Birkeland

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Offline greg788

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Re: 220 ohm Resistor Wattage?
« Reply #2 on: October 02, 2022, 04:37:13 AM »
Should RP-G2 be a wirewound instead of carbon film since it appears to be the grid stopper? Or being a single stage with zero feedback, is oscillation at radio frequencies N/A here?

Online Paul Birkeland

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Re: 220 ohm Resistor Wattage?
« Reply #3 on: October 02, 2022, 05:33:55 AM »
A non-inductive part is a good idea for a grid stopper, so a wirewound is really the worst choice for that.  We used to provide carbon composition resistors for this particular spot because they are completely non-inductive, but they are also fragile and like to snap if they get moved around too much.  The carbon film resistors we supply are a happy compromise. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline greg788

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Re: 220 ohm Resistor Wattage?
« Reply #4 on: October 02, 2022, 09:51:18 AM »
Aside from the line level 220 ohm resistors, which other ones do you feel are worth upgrading? For example, I have my eye on the RL, which is the 10K wire wound. And if I upgrade those, should I stay with wire wound like a Mills? Replacing the stock 220 ohm carbon films with 1/2 watt Takman carbon films seemed to provide a minor improvement in smoothness

Online Paul Birkeland

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Re: 220 ohm Resistor Wattage?
« Reply #5 on: October 02, 2022, 02:04:43 PM »
The 10K plate load resistor will be removed with the first upgrade.  The little 150uF cap could be replaced with something else, and that cap is very much in the signal path.  220uF/16V is a reasonable alternative value that's probably more commonly found.
Paul "PB" Birkeland

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Offline greg788

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Re: 220 ohm Resistor Wattage?
« Reply #6 on: October 02, 2022, 04:24:16 PM »
I may not do the upgrade so is 10k wirewound worth upgrading? And should I stay with wirewound or would an audio spec (non-magnetic) 5w metal oxide be a better bet?

Online Paul Birkeland

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Re: 220 ohm Resistor Wattage?
« Reply #7 on: October 02, 2022, 04:30:02 PM »
I think a metal oxide would be a downgrade from the wirewound we provide.  A Mills resistor would work just fine.

A constant current source is the best choice for replacing this part.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man