Always. Check. The. Resistor. Values. Don't. Trust. The. Label.

Discussion in 'DIY' started by No Money, Jun 11, 2017.

  1. No Money

    No Money AK Subscriber Subscriber

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    So, I'm fixing something for a friend. Among other things it had a few resistors that had drifted somewhat so pulled them and ordered some new ones as part of a big order for an upcoming project. Put them in and then started to test the circuit. Hmmmmmm. Thats weird, those readings are way off. Scratch head and leave it a day. Come back and try again. Same result. OK, thinks it might be something I changed. Grab the bags from the supplier and start checking the spares in the bags. A HA, 22 ohm resistors that are actual 1.6M ohm ....

    Some new 22 ohm's on the way (I hope). That will teach me not to rush.

    Or as my father would say, measure twice, cut once.
     
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  2. gadget73

    gadget73 junk junkie Subscriber

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    never had one that far off. Usually its more a mistake on my end, mis-reading the color bars. Actually thats why I tend to check values before installation, just to make sure red isn't orange or whatever.
     
  3. Binkman

    Binkman Addicted Member

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    Not to offend? Check resistor reference chart if in doubt. Ummmm did the bands reference as 22ohms?? like a factory screw up?

    Hey I check my band chart frequently, sort of a memory reminder and some bands look worn and a few that actually looked orange instead of yellow per crap film inside cabinet or just lousy banding. Even when receiving for a company, I'd be asked to measure lots for pcb asm when tech was off.. found more than few mis-banded lots or just didn't measure up.
     
  4. No Money

    No Money AK Subscriber Subscriber

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    I'm a bit red green colourblind so have a hard time with checking the bands. I use a meter. In this case the ones delivered were most definitely wrong. I checked them with the tester and also a complicated ocular algorithm, or in other words I got someone with better colour vision to look at the bands. They confirmed them as 1.6M ohm.

    Someone, somewhere down the line put the wrong resistors in the wrong pile and then, eventually sent them to me. Have emailed the supplier to let them know. Mistakes happen. I'm just glad I caught it early. I also hope they haven't sent huge numbers out ...
     
  5. No Money

    No Money AK Subscriber Subscriber

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    I usually check, and have never found a mistake in an order before. For some reason I didn't this time. Got complacent.
     
  6. Bob

    Bob AK Subscriber Subscriber

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    because it's the time not the money, doing it right saves so much. I usually do each component
    one at a time, pull and measure, measure replacement and solder in. this verifies the
    schematic to the parts layout to the original part to the replaced part.

    sound like a lot of work and time, but once you have a rhythm it goes pretty fast and eliminates
    the mistakes.
     
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  7. No Money

    No Money AK Subscriber Subscriber

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    I'm going with the "once bitten, twice shy" rule from here in. Don't want to have to go through all that again.
     
  8. Alan0354

    Alan0354 Super Member

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    One time, I bought on ebay from China and the value was wrong on one particular value....that is the resistance is no where the same as the color band indicated. I never have problem with the ones from Digikey.

    For through hole, I actually measure every single one before I put it on the board, never once I seen wrong value, period. I am not consistent in check the values of the SMD resistor, just lazy, I do check like about half. I never have problem with the SMD resistors. BUT I would never buy from China, always from Digikey, Mouser or Newark. This is too important to try to save a little money.

    On the side note, I only buy capacitors, transistors from Digikey, Mouser and Newark. Only the very reputable places. I once bought an OPA2604 dual opamp on Amazon from some seller because it is not available in DIP8. But later, I found an adapter to use SO8 into DIP8 socket, so I bought the SO8 from Digikey. The square wave response is not the same between the real one and the one from Amazon. I have a suspicion the one on Amazon was fake.
     
  9. No Money

    No Money AK Subscriber Subscriber

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    These weren't from a China supplier, they were from a very reputable source. Just to make it clear, the resistors were correctly marked as 1.6 Ohm, but the bag said 22 Ohm. Someone made a small mistake in the logistics line.
     
  10. BinaryMike

    BinaryMike Pelagic EE Subscriber

    I overheated a pair of 10K 2W resistors in an amplifier prototype that I'm currently working on, and now their markings look exactly like 100 ohm resistors. No change in actual resistance value. These are modern metal oxide film parts from Mouser or DigiKey, sized about like older 1W resistors.
     
  11. stonedeaf

    stonedeaf Well-Known Member

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    854
    My great uncle had several properties near the Allen-Bradley plant in Milwaukee. For reasons no one understood ?- the pigeons would fill his gutters with resistors. One of my Dad's side jobs was fixing TV's -one of my childhood choirs was measuring literal buckets of 1/4 to about 5 watt resistors -completely random of course and a fair number not marked with colour bands. I did recently buy some 2 watt resistors from my local American Science and Surplus store - love that store - but not for resistors -tested them first and they were just wildly off from the values marked on the parts bags.
     
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  12. Binkman

    Binkman Addicted Member

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    LOL... perhaps they were factory trained inspection pigeons? I've read some pretty unbelievable stories but as implausible as it seems, I believe it. weird.
     
  13. KKnight

    KKnight Active Member

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    Always check manually anymore and do not rely on any band coloring or markings. Seems to be a trend the last couple of years. Even had the infamous Mills resistors (new) so out of spec had Mills and PE fighting with each other on who is liable. Vishay about the same way even for their expensive top of the line series. There really is no such thing anymore as a 'reliable' manufacturer or supplier, and good QC is a thing of the past. Its ALL coming worldwide from just a few plants in China, either whole or in parts, then to other manufactures to modify or stamp their name on them or directly to the supplier.
     
  14. Alan0354

    Alan0354 Super Member

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    That's the problem moving all the manufacturers to China. I hate to keep saying this as I am a Chinese!!!!:eek2::yikes:!!!!

    I always have a habit of checking with meter before I put it in, it's too important not to.
     
  15. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    I was OK while the resistors had 3 colour bands and one tolerance band, I could convert the colours to values instantly. But now with 5 and even 6 band resistors being common, until I get used to the layout of the bands I too measure resistors before putting them in. Several times when I've looked at one of those 5 or 6 band resistors and thought '150ohms - you have got to be kidding'! - and measured it only to find that it is 150ohms. :)
     
    Last edited: Jun 13, 2017
  16. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    I always like to measure each component before I put them in. It helps me remember where I'm at in the project as well. I took a 150k out, measure, ok here's a 150k to put back.

    I've luckily never received the wrong parts though I have repaired an amp where someone replaced a few resistors all willy nilly like, and it took me a while to figure out why the voltages were so off when the components checked good.
     
  17. Bob

    Bob AK Subscriber Subscriber

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    you can't blame the Chinese - I would doubt that one or more resistors/caps on a tape is
    an incorrect one. It may be the jobbers, distributors, middlemen that hire cheap labor
    and you get the end result of one or two incorrectly bagged components.

    here in the good ole USA, there was a saying about buying American cars on certain days due
    to bad attitudes on the assembler's part. These are guys who made the best bucks, had a
    strong union behind them, brought GM/Ford/Chrysler to their knees with strikes, and you
    could retire on a full pension before you were 40, and have lifetime medical.

    so, it's everywhere and you have to protect yourselves. Measure the old part as you take it
    out, and measure the new part as you solder it in.
     
  18. Alan0354

    Alan0354 Super Member

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    It was wrong value from the color bands.
     
  19. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    If every customer in the entire world (or hell, just 'enough of them') demanded better quality or they wouldn't buy, this would be better. But electronics manufacturers and parts vendors and we ourselves put up with it, I guess, in the race to the bottom on price. I have a feeling the Chinese or anybody else are capable of getting it right, given the proper motivation.
     
  20. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Regarding wrong parts - I got 11V Zeners, marked on the bag as 13V from a UK supplier. I rang them up and spoke with a manager for quite a few minutes repeatedly restating my case that "I know what I received and it isn't right", before she finally backed down and agreed to send the correct parts - FOC and double checked before dispatch. :)
     

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