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Old 31st Jul 2021, 9:05 pm   #1
Murphy Maniac
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Default Resistor Wattage?

Good Evening All,
Can someone please help by telling me the wattage of the 820R resistor in the photo?
Will it be comfortable at 4W?
Thanks.
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Old 31st Jul 2021, 9:27 pm   #2
GrimJosef
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Default Re: Resistor Wattage?

It's a vintage carbon film resistor (used to be called 'cracked carbon' and/or labelled 'high stability'), made by Piher. I'm afraid it won't be comfortable at 4W. They certainly made them in 1/2W, 1W and 2W versions and possibly in smaller sizes too. But I don't think any were rated higher than that. I think yours is the 2W size, but I'd need to extract one from storage and measure it to be sure.

Cheers,

GJ
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Old 31st Jul 2021, 9:32 pm   #3
Cobaltblue
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Default Re: Resistor Wattage?

I agree with GJ looks like a 2 Watt'r

I think I would be using a nice 7W wire wound if it were to be dissipating 4W continuously.

Cheers

Mike T
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Old 31st Jul 2021, 9:44 pm   #4
60 oldjohn
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Default Re: Resistor Wattage?

Quote:
Originally Posted by GrimJosef View Post
It's a vintage carbon film resistor (used to be called 'cracked carbon' and/or labelled 'high stability'), made by Piher. I'm afraid it won't be comfortable at 4W. They certainly made them in 1/2W, 1W and 2W versions and possibly in smaller sizes too. But I don't think any were rated higher than that. I think yours is the 2W size, but I'd need to extract one from storage and measure it to be sure.

Cheers,

GJ
I think GJ is correct, I have a packet branded "RS" 2W high stability carbon film, which I have just measured.

Crossed with Mike.

John
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Old 1st Aug 2021, 12:31 am   #5
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Default Re: Resistor Wattage?

Thanks for that, I very much feared that might be the case.
Having searched through the thousands of resistors which I have in stock, unfortunately, I have nothing suitable. 820 ohms, although a prefered value, does not seem to be available as 7W or 10W W/W.
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Old 1st Aug 2021, 7:40 am   #6
HamishBoxer
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Default Re: Resistor Wattage?

That is a Radiospares 2W and No more.
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Old 1st Aug 2021, 8:01 am   #7
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Default Re: Resistor Wattage?

RS have a few... e.g. https://uk.rs-online.com/web/p/throu...istors/4852962

Andy
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Old 1st Aug 2021, 10:54 am   #8
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Default Re: Resistor Wattage?

Brilliant, thanks Andy.
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