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Thread: Help identifying a resistor please.

  1. #11

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    Quote Originally Posted by acollins22 View Post
    Thank you everyone for your replies.

    I read its companion both ways round and it is indeed 510 Ohms (minus a smidge) so I have replaced it with a new one.

    Attachment 57059
    Looking at the size or the original compared to the 1/4w replacement, I wonder if it was 1/8w. anyway, it's gone now!


    Thanks again all,

    Andy.
    1/8w carbon comp. Those would be hard to find. I think a 1/4w carbon film will work fine there.
    Dwight

  2. #12
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    Gold - 5%, Silver - 10%, None - 20%

    HTH,
    Tom

  3. #13

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    Quote Originally Posted by hornbetw View Post
    Gold - 5%, Silver - 10%, None - 20%

    HTH,
    Tom
    I keep forgetting the no band. It has been a long time since I've used a carbon comp for any thing. At 20%, one wonders why they even bother to put a value on it.
    Dwight

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    It's a carry-over from the valve (electron tube) days, where resistors were not very precise, and it didn't matter that much anyway on such equipment. The idea of a tolerance band didn't exist then, so for uniformity 20% was assumed.

  5. #15
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    I stared at the enlarged photo of the intact resistor and will almost swear that there's a faint gold band there, which led me to the 5% opinion.

  6. #16

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    Quote Originally Posted by Chuck(G) View Post
    I stared at the enlarged photo of the intact resistor and will almost swear that there's a faint gold band there, which led me to the 5% opinion.
    Even if it was label as a 5%, if it were used anywhere near its rated value, it is lucky to be 20%. When I was in the service, I replaced a lot of 5% carbon comps in circuits that did care. Yes it was tube circuits but there are a few cases that cathode resistor values are important.
    Dwight

  7. #17
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    I recall the old puzzler. A young engineer looks at resistor pricing and figures that if he purchases a 1000 lot of 20% (or 10%) carbon comp resistors and only 25% of them fall in the 5% tolerance range that he's saved a bunch of money by tossing out the ones that fail to meet 5% of marked value. After all, the yield should follow a bell-shaped normal distribution curve, right?

    He gets his 1000 20% resistors and finds that none of them are within 5% of marked value.

    Why is that?

  8. #18
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    Quote Originally Posted by Chuck(G) View Post
    I stared at the enlarged photo of the intact resistor and will almost swear that there's a faint gold band there, which led me to the 5% opinion.
    I've never seen an allen-bradley style resistor with a 5% tolerance. They're usually 20% or less commonly 10% (silver band).

    I have a box of thousands of them I got from an old Motorola engineer, none have a 5% tolerance.

  9. #19
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    Allen-Bradley style? Do you mean carbon comp with a phenolic encapsulation? How would you tell one, say, from an IRC or Erie resistor?

  10. #20

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    Quote Originally Posted by GiGaBiTe View Post
    I've never seen an allen-bradley style resistor with a 5% tolerance. They're usually 20% or less commonly 10% (silver band).

    I have a box of thousands of them I got from an old Motorola engineer, none have a 5% tolerance.
    The manufacture made several thousand resistors. Those that were within 5% got gold bands. Those that were within 10% got silver bands. Those that were within 20% were not marked with a band. The rest were either marked 750 or 330, assuming he bought 510 ohm resistors. The rest were tossed as they didn't trust them.
    Dwight

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