Fried chips - Page 1
Forum section: electronics / beginners

author: steve30
author_rank: Frequent Contributor
timestamp: December 22, 2012, 03:06:42 pm
content: Does anyone else find they get loads of chips which just randomly fail?I've had two LT3080s fail recently, an LM10 failed the other day, and a few months back, a load of 74HCT86s failed.I've also had things like analogue to digital converters fail for no apparent reason.In all these cases I don't think I did anything nasty to them, but of course I can't rule that out. Just seems completely random.

author: Kremmen
author_rank: Super Contributor
timestamp: December 22, 2012, 03:16:54 pm
content: Where did you buy said chips? You sure they are not erm... "second source"? I understand faking semiconductors is an increasingly common pastime in certain corners of the world.

author: steve30
author_rank: Frequent Contributor
timestamp: December 22, 2012, 03:19:16 pm
content: Most are from RS or Farnell, so I doubt they are fake.I can only imagine I did something which upset said chips.

author: AndyC_772
author_rank: Super Contributor
timestamp: December 22, 2012, 03:30:56 pm
content: Chips very, very rarely "just fail" under normal use. They do, however, fail when subjected to stresses outside of their design limits.Do you take proper ESD precautions every single time you handle an IC?

author: ivan747
author_rank: Super Contributor
timestamp: December 22, 2012, 03:31:38 pm
content: Is the weather dry and/or cold? You may be ruining the chips with ESD.

author: Bored@Work
author_rank: Super Contributor
timestamp: December 22, 2012, 03:33:05 pm
content: Your lab power supply not being so "lab" at all?

author: steve30
author_rank: Frequent Contributor
timestamp: December 22, 2012, 04:08:58 pm
content: All I can think of is ESD. Maybe I should get an ESD mat and a wrist strap.Don't think its too dry in here. Tends to be hot though. Well into the 20s in winter (with the heating on) and >30 in summer.Funnily enough though, I never seem to damage transistors.

author: Short Circuit
author_rank: Frequent Contributor
timestamp: December 22, 2012, 04:33:04 pm
content: How did you power them? Transistors usually have much higher voltage range than ICs...

author: SeanB
author_rank: Super Contributor
timestamp: December 22, 2012, 04:53:00 pm
content: Transistor junctions are much bigger. An event that will destroy a IC junction that is 5000000 times smaller than the transistor will not even be noticed by the transistor. As an analogy a hay straw will pop a balloon but will have no effect on a truck tyre.

author: Electr0nicus
author_rank: Regular Contributor
timestamp: December 24, 2012, 10:35:12 pm
content: Quote from: Bored@Work on December 22, 2012, 03:33:05 pmI (still) have a lab- power supply from a well known German company, which specialises on selling their products (Powersupplies, Frequency generators, battery chargers etc.) as fully assembled and, as a second option, as a kit to assemble yourself.A neat idea of course. But their "products" are often very shitty.So I happened to buy that linear 300W PSU as a kit. I built it up and it worked just fine. I still had the oscilloscope probes (which I used to measure the output ripple) attached, when I switched the PSU off via the "real" mechanical mains power switch. Suddenly I got a 34V 20ms long peak on the output of the PSU, showing up on the oscilloscope, which is really unacceptable. I narrowed it down to the back EMF from the huge relay, that switches in another transformer tap. I fixed the issue, so no more voltage peak occurred on the output.After all, I emailed the company about the problem, expecting that they will react properly. But nothing this way happened. They wrote me back, saying that they neither won't investigate further, nor release any errata, because there was nobody up to now, who pointed out a similar problem. So it can't exist in their opinion.WTF!.Since then I'm not very well to speak on that company.So even if your PSU looks very "lab" on the outside, is there actually "lab" inside?Cheers Gregor

author: c4757p
author_rank: Super Contributor
timestamp: December 24, 2012, 11:48:58 pm
content: I generally assume that unless proven otherwise, a power supply should not be switched on or off with a load connected.

author: steve30
author_rank: Frequent Contributor
timestamp: December 25, 2012, 12:06:13 am
content: That's probably a good precaution to take.I've not seen any overshoot or similar issues on my PSU, but I am adding a Load On/Off switch to to be on the safe side.

author: free_electron
author_rank: Super Contributor
timestamp: December 25, 2012, 12:35:20 am
content: Quote from: Electr0nicus on December 24, 2012, 10:35:12 pmELV ? their designs are generally pretty good ...Now on the oft failing chips: i suspect also that the TS power supply may have stability problems... especially on power up power down.

author: Electr0nicus
author_rank: Regular Contributor
timestamp: December 25, 2012, 01:44:42 am
content: Quote from: free_electron on December 25, 2012, 12:35:20 amYou've guessed it. I won't deny that they have some pretty awesome stuff, but there are also sometimes issues with their circuits. That's no drama at all, but if someone finds a problem with a circuit, and also gives them the solution of his investigation, and they ignore it completely is really unacceptable. So I won't buy anything from that company again. Btw the PSU i'm talking about is called "PS 9530".