Yet again today we found a fake chip, but only after fitting it into an old amplifier and then a good hour or two of painful troubleshooting.
I’m familiar with the basics of avoiding counterfeit chips like checking the markings, verification of sources etc.
Does anyone have any suggestions for test equipment that could help us? Often the fakes will have a transistor of sorts, so a component tester shows a working device. But it will fail under load, or won’t meet the slew rate etc.
Thanks!!
Very tough question to answer. Personally, I believe if you build the test circuit on data data sheets, you are good - but no one will do this, and me neither, unless you need a larger quantity.
methods I have seen done by at least two people, is to xray the part, but often only works on complex components, and the internal shadows and organisation look different - someties
Some have tried a resistance test and diode check between a known working good and the suspect.
The other way is that the laser often is not set to etch markings in the same way and depth, including logos in different positions, or without the logo being as vivid as the original. People place the two components side by side and look for differences
One person on yt (learn electronics) had an issue with fake transistors, so built a circuit that put 8A through a transistor rated at 8A, and the current can be scaled down too.
Ideally we should have a list of good and bad suppliers.
If a user needs components, I normally get the to buy British (quality reasons, not cost) or send the to Cricklewood Electronics, as they can be cheaper than RS, and offer a decent turnaround. The problem I had with them that they could not match the smaller electrolytic sizes, as I asked the visitor to make sure they got the caps of the correct size - it was a visit in person.
All good advice, thanks!
I think for the replacement chips and any future ones we are suspicious of, we will have to build up a test circuit. We have power supplies, pots, etc but it’s just a lot of bother to go to, I’m annoyed we have to do it.
I was half hoping there was a £30 gadget from Ali express that did it for me!
Forgot to mention another thing to look for on tht components for shorter legs, or the obvious tinned leg tips.
How to remove components on mass
Get a tumble drier or washing machine. Remove the door and safety switch and set it to a slow.
Insert the PCB’s into the machine.
Get a propane space heater and point the heat output at the open door hole.
Perhaps someone could make money from these selling second hand parts, like they do in China?