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Forum Index : Microcontroller and PC projects : GreatScott on fake components....
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| Tinine Guru  Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
Interesting findings Craig |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
Very interesting. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5119 |
I've bought a couple fake SSR's off ebay, usually the 40A model. On closer inspection they contained a power transistor rated for 5 amps, not a MOSFET rated at 40 amps plus safety margin. Also bought fake conductive paint that was plain old silver paint and a pretty good insulator. So I leave a bad review, which is followed by the seller offering a replacement or money back in exchange for removing the bad review. But I dont, I leave the bad review up as a warning to other buyers. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 655 |
  G'Day All We have a CCTV system that has worked for some years but recently started displaying horizontal lines on one camera. The 5 lines were caused by 50Hz interference. After a process of elimination, it was this BALUN. So how did it happen? All I can think is that it was a factory reject, repaired by by-passing the transformer and sealed up. And so it worked for years until one of the windings went OC and acted as an antenna or black magic does exist or ????? I am also a bit concerned that there is probably another 11 still in the system. A week later one of the 12V coaxial connectors went OC but on a different camera. Peter(B) |
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| pwillard Guru Joined: 07/06/2022 Location: United StatesPosts: 313 |
I agree that we probably end up buying a lot of factory rejects versus parts being purpose-made counterfeits. A while back I bought some LM350 (TO-3 CASE) regulators from an EBAY seller. I waited about 2 years before I finally built the PCB and finished the project. While testing it, I blew out the unit at 800mA load which just isn't right for a 3 AMP device... but it did regulate correctly until it broke. I did some forensics (I cut off the top of the metal case) and the error mode was very clear. It had a single small spot-welded wire from the die to the output pin which had acted just like a fuse. Had a larger wire or better "multiple wires" of that gauge been used... it would have been OK. Oddly enough... there were 2 parallel lead wires on the input pin. |
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Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
Yes, I have been bitten by this more then once. Basically, the age-old saying: "If it looks too good to be true, it probably is" applies here. I quit buying cheap parts from eBay or AliExpress years ago cos of this kind of thing. Buy parts ONLY from certified suppliers. Much more expensive per part price, yes, but at least you know you will be getting the genuine article, and not a clone or an outright fake. Smoke makes things work. When the smoke gets out, it stops! |
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| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 655 |
G'Day Grogster & pw I stopped buying from Banggood some years ago and Aliexpress more recently however our CCTV system was installed by a big company and it came with a big price. Sadly we can never be sure. Peter(B) |
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| pwillard Guru Joined: 07/06/2022 Location: United StatesPosts: 313 |
The balun bypass is a sick joke, tbh. |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
My Qty:100 CD4050BE shipment arrived today. I did some random sampling and this is clearly a failed production batch. Of the 6 channels, channel #2 is dead on every sample I tested. I'm cool with it though. As long as I know, I can live with 5 channels and I won't be using them in customer-products. Compared them with my "real-McCoy" 74HC4050s which can take a straight 5V on any input and provide 3.28V on the output. These particular CD4050BEs...can't do that because there is some clamping-diode-or-other. Current limiting with a 330R on the 5V signal and all is good.   Craig |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5090 |
If you need the ones without clamping diodes, isnt that the CD4050U? PicomiteVGA PETSCII ROBOTS |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
I haven't checked yet but I do know that it's a different part number Craig |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
Is there a CD4050U ? I know there's a CD4049U and IIRC that's an inverting version of the CD5050. AFAIK they all have protection diodes on the input as the input isn't supposed to ever exceed VCC. I'd have to chase down some data sheets... Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
I remember a comment that was something like "be careful because the older CD4050s had a protection diode" but I left it at that. For the job at hand, I have big-name-sourced 74HC4050s which work without fuss  Craig |
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| Tinine Guru Joined: 30/03/2016 Location: United KingdomPosts: 1646 |
 This is all I ever see BUT without a few hundred ohms to limit the current, they just shut down(!?!?!?) I'll never get along with datasheets  Craig |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
Found a data sheet. CD4049UB and CD4050B are identical except that CD4050B has an extra MOS pair on the output to convert it to non-inverting. The input circuit is the same, with protection diodes. Yep - the diode to VCC is reversed so you can exceed VCC on the input. The diode to gnd prevents the input from going negative. Then there is a series resistor (value unknown). You must limit input current to less than 10mA. If you are having problems with them latching up it may be that VCC is too low or that there is too much input current. Edited 2022-06-15 17:20 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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