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Old 1st November 2014, 09:48 AM   #1
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Default resistor recomd

Hi And thanks for reading this post.

Not sure where to put this question but i am going to buy a few resistors for my amp repair the vishay cmf series, perhaps known as rn or rl, is this right?

According to the data sheet these should be one watt resistors but when i went to mouser to purchase them they were labelled as quarter of a watt, what am i missing

Many thanks. John.
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Old 1st November 2014, 10:40 AM   #2
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Try this list; Resistors | CPC | Results
or here ; Y010120K0000T0L Vishay Precision Group Foil Resistors | Mouser
There are many suppliers, Farnell, RS Components etc.
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Old 1st November 2014, 02:25 PM   #3
AndrewT is offline AndrewT  Scotland
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or you could use two 600mW resistors.
Either in series for lower voltage across each or in parallel for lower current through each.

At 1.6p each that comes to 3.2p+VAT.
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Old 2nd November 2014, 07:01 AM   #4
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HI. Thanks for the replies, much appreciated.

Got my heart set on the cmf 60 sorry to be so stubborn, they fit the board and the price is ok.just wanted someone to confirm if they are one watt resistors or not,

Are they the same as the RN-60 and RL-60?

On mouser search results under " description " the cmf60's are said to be half a watt, and under " power rating " they contradict this and say they are quarter of a watt.

The RN's are stated to be quarter of a watt and then half a watt, the Rl's are stated to be half a watt.

But the data sheet says something else, sorry hope this is making sense.

Many thanks . John.
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Old 2nd November 2014, 08:09 AM   #5
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Google the data sheets and read for yourself why this is going to be a difficult and frustrating exercise.
RN60,70 or RL60,70 etc is the military style specification coding which begins a long military part number series and it gets confusing; some are historical and others current series and some are global/ part numbers. RN types refer to Precision and RL to Qualified specifications. These only have to do with military performance requirements and have little to do with audio components other than the numbers look impressive and the parts cost more for the quality assurance stocking procedures and certification.

If you are following what you read on other forums, don't be surprised that the advice only applies to one grade, one rating series according to the post's requirements. When for instance, power ratings are changed, its normal for many other specs to change, along with the physical dimensions so you may have difficulty buying the same grade in other ratings that you may want. CMF is a composite range of both RL and RN groupings but remember these codes are meant for military classification. Good luck sorting that mess out if you want to persue it.
See page 2 of Vishay's datasheet for a start point:
http://www.vishay.com/docs/31027/cmfmil.pdf
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Old 2nd November 2014, 08:34 AM   #6
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Sorry, i didn't understand much of what you said.

Just want to know if the current cmf's are one watt rated,

You are right, on farnell they are stated as one watt, on mouser they are half a watt, the same for RN and RL.

The military specs for power rating should be doubled managed to figure that much out.

Any more input please.
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Old 2nd November 2014, 09:12 AM   #7
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goodguys, read the Vishay datasheet. CMF is a Global (composite) classification - not a single grade, type etc. Don't confuse what those groupings mean with commercial specifications like Koa Speer MFS1/2 type for example.

Look at the first table showing the breakdown of CMF into both RN and RL classifications. Then decide whether you have to buy RN or RL type and which power range according to what ranges are available.
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Old 2nd November 2014, 09:48 AM   #8
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The confusion around the CMF classification is probably due to Vishay also using it as an industrial classification. Perhaps this is where the apparent conflict arises so take care and refer to the correct tables. Some are specifying tolerances or test results, not ratings so only look at the first table in the datasheet link below. Note the range offered is 0.25-1.75W but there are 2 power ratings, for 70 and 125 degree C operation and if you look at CMF60 industrial spec, it's rated both 1 and 0.5W accordingly:
http://www.vishay.com/docs/31018/cmfind.pdf
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Last edited by Ian Finch; 2nd November 2014 at 10:11 AM.
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Old 2nd November 2014, 04:24 PM   #9
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Why not just get some generic 1W resistors? Performance will be the same, price will be lower - and best of all: No confusion. Isn't that just lovely?
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Old 4th November 2014, 03:58 AM   #10
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Thank you for the much appreciated replies.

Big Up @ Ian Finch

Kudos Points @ Welcome

Diamond Geezer @ Andrew T

The Daddy @ Jon Snell
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