Author Topic: Warning- LM317K duds from Digikey  (Read 9675 times)

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Offline David AuroraTopic starter

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Warning- LM317K duds from Digikey
« on: January 08, 2025, 02:42:43 am »
Just a quick heads up in the hope nobody else loses hours of time like I just did- these "new" LM317K regulators they have in stock don't even come close to meeting spec https://www.digikey.com.au/en/products/detail/evvo/LM317K/25188516

I just watched 3 in a row eat shit in a bog standard regulator circuit as soon as current draw exceeded around 1A. Not a thermal thing either, in every case they worked unloaded or at half an amp or so but died instantly once I increased the load.

I don't think I've ever gotten fake parts from Digikey before so I spent ages double checking everything around them but couldn't find an issue. Then when I threw in some replacements from a different brand the power supply fired up like it's supposed to and has already been stress tested hard for about an hour without a hiccup.

Digikey were super fast with their response and have already credited me for the purchase, but who knows how long they'll still be up on the site for purchase so take my advice and don't touch them with a ten foot pole.
 
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Online wraper

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Re: Warning- LM317K duds from Digikey
« Reply #1 on: January 08, 2025, 03:09:07 am »
What was input voltage?
 

Online squadchannel

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Re: Warning- LM317K duds from Digikey
« Reply #2 on: January 08, 2025, 03:12:43 am »
EVVOSEMI?
There have been a unknown and unheard of manufacturers making their way onto Digikey recently. :--

search on Digikey, I always narrow down the manufacturer.

to-3 maybe hard to find.

TI is $130  :wtf: very expensive  :palm: maybe Hi-rel products.
« Last Edit: January 08, 2025, 03:16:44 am by squadchannel »
 
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Offline TimFox

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Re: Warning- LM317K duds from Digikey
« Reply #3 on: January 08, 2025, 03:20:16 am »
I had exactly the same problem with TO-3 317s from another vendor:  they would pop immediately when the load current exceeded a critical value.  They should have gone into thermal limiting and survived.  I’ll try to find the details.
« Last Edit: January 08, 2025, 03:22:13 am by TimFox »
 
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Offline floobydust

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Re: Warning- LM317K duds from Digikey
« Reply #4 on: January 08, 2025, 04:50:01 am »
WTF the EVVOSEMI schematic pass transistor is not a Darlington, but has Sziklai pair which smells like the '1117 but it's a lower voltage IC.
LM317K STEEL I used back in the late 1970's in my first power supply, a faithful horse.
 
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Online coppercone2

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Re: Warning- LM317K duds from Digikey
« Reply #5 on: January 08, 2025, 04:59:04 am »
one of the biggest features the LDO has going for it is the thermal shutdown. Its like the only reason you would parallel up LDO instead of using a pass transistor. !!

I would not call it out of spec, I would call it defective.

I use those parallel circuits that are shown in some data sheets because... each chip has a integrated over temp protection. you lose the feature when you start going with external transistors. In this case, if it breaks, why the hell would you bother??

big fail :-BROKE
« Last Edit: January 08, 2025, 05:03:44 am by coppercone2 »
 
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Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #6 on: January 08, 2025, 05:15:18 am »
What was input voltage?

Nah it was not an input/output voltage issue. This is from a mixing console that had survived with the original regulators for 30 years (it failed after the owner shorted something on a DIY servicing attempt) and with a different brand of regulators appears fine too. Issue is specific to these ones Digikey are selling.
 

Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #7 on: January 08, 2025, 05:18:23 am »
EVVOSEMI?
There have been a unknown and unheard of manufacturers making their way onto Digikey recently. :--

search on Digikey, I always narrow down the manufacturer.

to-3 maybe hard to find.

TI is $130  :wtf: very expensive  :palm: maybe Hi-rel products.

Yeah these were literally the only stocked version of the LM317K I could find from a reputable source unfortunately, usually I'd never touch an unknown brand like that. Who'd have thought I'd have had better results buying off eBay  :-//
 

Offline magic

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Re: Warning- LM317K duds from Digikey
« Reply #8 on: January 08, 2025, 07:50:29 am »
Who'd have thought I'd have had better results buying off eBay  :-//
Maybe better or maybe same :P

WTF the whole thing, including DigiKey not noticing that this isn't even claimed to be a true 317 circuit. Maybe it went into suicidal oscillation with whatever capacitors are present in the circuit? (Assuming that the schematic found by floobydust actually represents what's inside - 1117 is not as stable as 317).
 
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Offline AVGresponding

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Re: Warning- LM317K duds from Digikey
« Reply #9 on: January 08, 2025, 10:50:15 am »
WTF the EVVOSEMI schematic pass transistor is not a Darlington, but has Sziklai pair which smells like the '1117 but it's a lower voltage IC.
LM317K STEEL I used back in the late 1970's in my first power supply, a faithful horse.

Maybe the battery that supplies the non-inverting reference of the current limiter is dead...
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Offline floobydust

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Re: Warning- LM317K duds from Digikey
« Reply #10 on: January 08, 2025, 05:48:37 pm »
Another option is the LT317K, LT317AK. I dumpster dived some new LT338AK from work, if you're in a pickle (jar) let me know. But these have much greater output current.

Many smaller Taiwan and china semi manufacturers are using the classic part number but selling you a "cost improved" redesigned part.
Example I got comparators slow as molasses 10usec switching times and at first thought I got ripped off. Then, digging a bit:
Unisonic LMV331 is 12usec  :o
TI LMV331 is 0.6usec, ST is 0.375usec, On-Semi 1.5usec

I complained to the vendor and they replied "we are just broker". Lesson learned.

I find Digi-Key uses their fine reputation to pimp for these unknown semi manufacturers, and the marketplace vendors as well. Not sure what loser MBA came up with this strategy.
It does piss me off, side loading disreputable vendors - for what exactly? They think they are a fulfillment center or something.
 
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Online thm_w

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Re: Warning- LM317K duds from Digikey
« Reply #11 on: January 08, 2025, 10:31:11 pm »
I find Digi-Key uses their fine reputation to pimp for these unknown semi manufacturers, and the marketplace vendors as well. Not sure what loser MBA came up with this strategy.
It does piss me off, side loading disreputable vendors - for what exactly? They think they are a fulfillment center or something.

Marketplace is fine, if it were off by default for searching, and only came up if nothing was found. Usually I go to digikey first to search for a replacement part even if they are obsolete. So if they can supply a marketplace product that is genuine, its of value.

The new semi manufacturers, some have really good niche products, like 3peak and Goford semi. Do they produce any garbage knockoffs? Don't know.

This EVVO looks like all they make is knockoffs: https://www.evvosemi.com/en/
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Offline Geoff-AU

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Re: Warning- LM317K duds from Digikey
« Reply #12 on: January 09, 2025, 03:56:36 am »
The EVVO datasheet Digikey links to has only 3 pages, the first is a title page, last is a disclaimer, and page 2 has "actual specs" including a pinout (but no pins labeled anywhere, which one is which?).  No logic diagram or anything, and it's 1/3 the price of anything else.

Shame on you, Digikey.  Shame on you.

 

Online wraper

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Re: Warning- LM317K duds from Digikey
« Reply #13 on: January 09, 2025, 04:44:32 am »
BTW isn't there some bipolar supply? I don't buy they are necessarily bad parts with no schematic or its description whatsoever. It may easily be they are less robust to something that goes wrong in your circuit, but part from another brand survives more of particular abuse than other. Circuit working does not necessarily mean it has no mistakes, oversights.
« Last Edit: January 09, 2025, 04:47:01 am by wraper »
 

Offline magic

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Re: Warning- LM317K duds from Digikey
« Reply #14 on: January 09, 2025, 08:37:49 am »
If you still have a surviving sample you could check dropout voltage to confirm if it really is a 1117 rather than 317.
Then make sure that input/output capacitors follow 1117 stability guidelines and try again.
Or test it at low voltage (less heat if things go wrong) and see if it's oscillating, drifting out of spec, or doing some other suspicious stuff.

What was the behavior of the "dead" ones?
« Last Edit: January 09, 2025, 08:41:04 am by magic »
 

Offline Ice-Tea

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Re: Warning- LM317K duds from Digikey
« Reply #15 on: January 09, 2025, 08:41:41 am »
That datasheet  :-DD

High level of "trust me bro!"
 

Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #16 on: January 09, 2025, 01:37:40 pm »
BTW isn't there some bipolar supply? I don't buy they are necessarily bad parts with no schematic or its description whatsoever. It may easily be they are less robust to something that goes wrong in your circuit, but part from another brand survives more of particular abuse than other. Circuit working does not necessarily mean it has no mistakes, oversights.

You don't buy they're bad parts, when 3 out of 3 failed and alternate brands don't? On a dead simple straight-from-the-datasheet-design regulator? That sounds like a you problem.
 

Online wraper

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Re: Warning- LM317K duds from Digikey
« Reply #17 on: January 09, 2025, 01:48:48 pm »
BTW isn't there some bipolar supply? I don't buy they are necessarily bad parts with no schematic or its description whatsoever. It may easily be they are less robust to something that goes wrong in your circuit, but part from another brand survives more of particular abuse than other. Circuit working does not necessarily mean it has no mistakes, oversights.

You don't buy they're bad parts, when 3 out of 3 failed and alternate brands don't? On a dead simple straight-from-the-datasheet-design regulator? That sounds like a you problem.
You provided no description of the circuit whatsoever. I'd trust Digikey selling working parts rather than someone refusing to provide any context of how they fail. How could they fail without being bad parts? For example you may have bipolar PSU with no reverse polarity protection on the output, high output capacitance with no reverse direction diode across Vreg, high inductance on the output. As I already said, the fact of parts from some manufacturers surviving in your circuit does not necessarily mean that circuit in fine.
« Last Edit: January 09, 2025, 02:07:25 pm by wraper »
 
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Offline Geoff-AU

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Re: Warning- LM317K duds from Digikey
« Reply #18 on: January 09, 2025, 11:14:02 pm »
I agree that usually the burden of proof lies with the designer, to prove that they haven't abused the part.  Few details of the failing circuit were given.

But in this case, given the datasheet....  they're junk parts.  Not worth the time publishing and defending a circuit design. 
 

Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #19 on: January 09, 2025, 11:45:45 pm »
BTW isn't there some bipolar supply? I don't buy they are necessarily bad parts with no schematic or its description whatsoever. It may easily be they are less robust to something that goes wrong in your circuit, but part from another brand survives more of particular abuse than other. Circuit working does not necessarily mean it has no mistakes, oversights.

You don't buy they're bad parts, when 3 out of 3 failed and alternate brands don't? On a dead simple straight-from-the-datasheet-design regulator? That sounds like a you problem.
You provided no description of the circuit whatsoever. I'd trust Digikey selling working parts rather than someone refusing to provide any context of how they fail. How could they fail without being bad parts? For example you may have bipolar PSU with no reverse polarity protection on the output, high output capacitance with no reverse direction diode across Vreg, high inductance on the output. As I already said, the fact of parts from some manufacturers surviving in your circuit does not necessarily mean that circuit in fine.

Not sure if you're going out of your way to be a shit stirrer or you're actually this daft, but I'll play along one last time.

First of all, I've already told you- it's literally the bog standard LM317 circuit seen in every data sheet ever written and about 10 billion products out there. A few caps, a couple resistors and some protection diodes. If you don't know what that circuit looks like you probably shouldn't be in this thread shooting your mouth off.

Second, as I also already mentioned- save for the studio owner blowing up the old regulator (I don't know exactly what he did, but the supply died while he was messing round doing a DIY recap of the board, apparently while he was probing something), the circuit has worked for decades with an old LM317 and is again working fine with a new one from a different brand. When 3 out of 3 of the Digikey ones failed within the first 60 seconds in the same circuit only an absolute muppet would be standing here blaming the circuit.

Third- Digikey provided a refund immediately without requesting returns or more than a one paragraph rundown of what happened. I'd bet dollars to donuts that means it's not the first issue they've had with these.
 
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Online bdunham7

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Re: Warning- LM317K duds from Digikey
« Reply #20 on: January 10, 2025, 12:29:01 am »
When 3 out of 3 of the Digikey ones failed within the first 60 seconds in the same circuit only an absolute muppet would be standing here blaming the circuit.

While I agree that a defective part is the most likely explanation by far, one not too farfetched possibility is that the circuit exceeds the specifications of the LM317K and the original and "good" parts also exceed their specs by enough to let them work without issue.  In this case the "bad" parts simply meet the specs and promptly blow up when they're exceeded.  I doubt very much that that is the issue, but it's not a ridiculous question.  Similar things have happened in other contexts. 

I've seen a similar issue with a TO-220 LM317 where the voltage would drop when loaded.  This was powering a very old 8088 controller board and under certain conditions the load would go up for a few CPU cycles causing a brownout or reset.  The issue was the apparent internal impedance of the regulator was too high and after I replaced it and bench tested the regulator with power supply, it behaved just like yours apparently did--at about 40-50% of rated current it just popped without the overheat protection or current limiting kicking in.  The regulator was a recent Amazon or eBay purchase (not by me).
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Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #21 on: January 10, 2025, 03:13:51 am »
When 3 out of 3 of the Digikey ones failed within the first 60 seconds in the same circuit only an absolute muppet would be standing here blaming the circuit.

While I agree that a defective part is the most likely explanation by far, one not too farfetched possibility is that the circuit exceeds the specifications of the LM317K and the original and "good" parts also exceed their specs by enough to let them work without issue.  In this case the "bad" parts simply meet the specs and promptly blow up when they're exceeded.  I doubt very much that that is the issue, but it's not a ridiculous question.  Similar things have happened in other contexts. 

I've seen a similar issue with a TO-220 LM317 where the voltage would drop when loaded.  This was powering a very old 8088 controller board and under certain conditions the load would go up for a few CPU cycles causing a brownout or reset.  The issue was the apparent internal impedance of the regulator was too high and after I replaced it and bench tested the regulator with power supply, it behaved just like yours apparently did--at about 40-50% of rated current it just popped without the overheat protection or current limiting kicking in.  The regulator was a recent Amazon or eBay purchase (not by me).

1A current draw does not exceed the specs of an LM317K. And it has nothing to do with circuit quirks either because the Digikey ones failed in both the unit itself as well as on a DC load.

I think what a couple of people are also missing here is that a genuine LM317 has multiple degrees of protection. So while I was using these as replacements in a circuit that is literally the typical application circuit in the datasheet that we've all seen 10,000 times(!), even if the designer had done something stupid like trying to pull too much current, giving them too much input voltage or inadequate heat sinking a genuine part should go into protection mode. These things appear to go open circuit permanently immediately upon the current draw hitting 1A or so.

I also notice that there doesn't seem to be any trace of an LM317K on this manufacturers website, it could be that it's a brand new offering from them and we're the beta testers, or it could be that they've already been pulled because of shit like this :-//
 

Online bdunham7

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Re: Warning- LM317K duds from Digikey
« Reply #22 on: January 10, 2025, 03:58:20 am »
I think what a couple of people are also missing here is that a genuine LM317 has multiple degrees of protection...... trying to pull too much current, giving them too much input voltage or inadequate heat sinking a genuine part should go into protection mode. These things appear to go open circuit permanently immediately upon the current draw hitting 1A or so.

We're aware of the protection features, but the one thing you have wrong there with protection is including input voltage--that will kill them instantly.  It isn't actually input voltage, it's the difference between input and output that matters.  One way protection functions can fail is when you have an input voltage higher than the maximum but the output voltage is also high enough so that the difference is less than the max.  Assuming that circuit survives startup, it will work fine until one day it overheats or gets overloaded and then right as the regulator either limits current or goes into thermal shutdown the max voltage spec is suddenly exceeded and it pops.  I think that's why the question arose. 

However, I think you just got regulators with the same crappy die that mine had and they went poof in the same manner and for the same reasons.  The input voltage question is mildly interesting because that crappy chip might also go poof at a lower-than-spec voltage differential and still work OK in a lot of circuits.  If you still have your original and fake replacement parts, perhaps peeling the can open and having a look would be interesting as well.
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Online squadchannel

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Re: Warning- LM317K duds from Digikey
« Reply #23 on: January 10, 2025, 04:02:44 am »
install a pot in an ADJ, VIN is within rating, Iout is within rating, and you use it normally, and it breaks, then it is either defective, designed that way, or are being stingy to keep it cheap.

curious what kind of die design it is.
if it is the same as the 1117 series, it will have to be broken.
1117 has an image of being easily broken.
 

Offline schmitt trigger

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Re: Warning- LM317K duds from Digikey
« Reply #24 on: January 10, 2025, 04:31:01 am »
If you still have an undamaged device, you may want to drop a line to Noopy, to see if he would be interested in taking some die pictures and compare them against other images of the same device. But different vendor.
 
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