EEVblog #133 - Dodgy Digikey Components

Dave cuts loose on Digikey (or Bourns?) for providing dodgy resistors which made their way into his µCurrent adapters.
Have you had dodgy parts from Digikey?
The part in question is this one:
CRT0805-BY-10R0ELF
And practical demos on how to do 4-Wire resistor measurements

[paparoysworkshop]

Back in the early 70's I read an article that talked of the importance of checking each resistor to verify it before using in any circuit that requires accuracy. Today, one would expect the manufacturing of the components to be higher quality then it was 45 years ago. But I guess that old advice still holds true today.

[stanburton]

Obviously this is an old post but this is precisely why the practice if removing the leading zero from values is a dangerous one. Ive fought this problem for years with purchasing agents, inventory clerks, engineers. Etc. That tiny little decimal point vanishes far too easily. But that big fat Zero doesn't.

[pibbles-a-plenty]

Well I'm sure Digi-Key will hear about this. Hah! Their buyers thought they knew how to avoid being snookered by Chinese alleyway manufacturers of fake components. Reminds me of Radio Shack's replacement semi's in the '70's. They were Texas Instruments culls. Just like then, and as it has always been, the QC department is right on your work bench, Dave

[circuitsmith]

George Carlin joke: "Everybody worries about all hell breaking loose. What if just a little piece broke loose and nobody noticed?"

[orsmplus]

After watching a bunch of these videos from almost a decade ago, its just dawned on me how amazing the video quality was in these videos, considering it was 2010.... Even in 2019 this is great

[rogeronslow]

Dave
Thanks for the excellent tutorial.
I've been in the electronics manufacturing industry for 25 years and learned that you ALWAYS test ALL your product specs during test and cal. That's been learned the hard way just as you have experienced. It does increase the cost slightly though.

[av]

The level of double triple checking you go through is outstanding, great stuff no mucking around at EEV!

[picobyte]

Are there crickets in your lab? Sounds like you have bugs.

[EEVblog]

@yanava Not in this case. The resistor is isolated with a mechanical switch. And the resistor was probed directly so traces have no effect. Capacitance does not matter for DC resistance measurements.

[laernulienlaernulienlaernu]

I would absolutely love any one of those really bang on meters, Dave’s got about twenty of the things just kicking about in his lab! The man’s got some kit!

[judclark]

I think this video shows that you have to verify everything yourself. Once you take ownership of those parts you are ultimately responsible for them and the results they produce in the equipment they get installed in. If you're going to sell a product you should also test your product to make sure it meets the specs you are guaranteeing to you customers. It's more costly not only in recalls and refunds but in reputation in the long run to sell dodgy gear.

[adisharr]

Digikey has always been solid for me. No component problems here In fact I just placed an order for some supplies that were supposed to ship UPS 2 day and they accidentally were keyed in on their end as UPS Ground. I needed one of the items fast (small BUD enclosure) and they shipped it to me free overnight at no charge.

I can't recommend them enough but I understand how something like this would be irritating.

[gregfeneis]

It's a risk that happens when Digi-key breaks down a manufacturer's packaging and puts a lot of resistors into their own packaging. They likely filled that packet from the wrong spool of components. The best you can do to work around a mistake like this is to only buy full spools that were straight from the mfg.

[billmoran]

The customer is always the final QA/QC inspector.

[shana_dmr]

I remember doing 4-wire resistance measurement on my introduction to metrology lab, we got 0.1 ohm reference resistor (one of these old, crusty big ones in big cylinder-shaped boxes) and we got 0.2 on 2-wire and 0.1 on 4-wire, that was a good eye-opener for someone trusting all you can get on the multimeter display (I was an IT student and this lab was kinda funny because most of students didn't even know an Ohm's law...) :)

[rocketsocks]

If he wanted 1.5% error components he would have spec'ed it out for that and he would have bought components to match those tolerances. A 10 ohm 0.1% SMD part costs $101.18 for a batch of 1000, whereas a 10 ohm 1% SMD part costs $12.59 for a batch of 1000 from digikey.

[SolutionByEvolution]

DigiKey has send the wrong part twice during various orders (~1% screw-up rate) and both times they squared me away but seemed like it was business as usual over the phone. I am trying different vendors such as Mouser to see if I get better results. This video and my prior experiences have strengthened my resolve to do parametric testing for each lot of parts received and to perform small initial builds that are to be tested extensively.

[KitCox]

Depending on how they are made they my be static sensitive...?! We had a class on static at one of our Western Union computer schools. They related a story of how a particular lot of super precision resistors made by a German company were all being measured slightly off when tested on the bench. Believe it was NASA, not sure. This was back in the late 1960's, before the era of anti static procedures & packaging, and ever shrinking conductor spacing. When they were removed from the paper envelope the Germans had packed them in, they picked up a static charge that was enough to arc across between two conductors, dragging a bit of molten metal from one to the other, shorting out a turn. That began the development of anti-static procedures, or so we were told.

[EEVblog]

@CampKohler No, no incoming component inspection apart from labeling, nothing unusual there, very common procedure. You build up confidence in your system and supply chain, but sometimes it lets you down like this.
The antistatic mat is just that, anti-static, or what's called "static dissipative", it is not conductive.

[theantipope]

So Dave, what was the outcome of this? Did Digikey say anything useful? How about Bournes?