Author Topic: Warning- LM317K duds from Digikey  (Read 9677 times)

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Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #100 on: January 22, 2025, 10:04:50 am »
Either way, if we assume a manufacturer is providing inaccurate data sheets and Digikey is still selling the part then why are you obsessed with trying to pin the blame on the end user for *checks notes* trusting a manufacturer and a supplier to make/sell a jelly bean part that has been around for nearly 50 years and sold by damn near every IC manufacturer that has ever existed? Get a grip.
I just suggest that you get a grip because this is the new normal :D

It's Shrödingers Regulator apparently- you claim the part is cheap Chinese shit, but simultaneously keep saying the part only failed because of some mystery misuse conspiracy. Pick a shit theory and stick with it, you absolute peanut.
Shit circuit, shit part, smoke goes out. What's surprising about that?

Wait, it's a shit circuit? I thought you kept saying I hadn't provided enough info on the circuit? Interesting.
 

Online temperance

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Re: Warning- LM317K duds from Digikey
« Reply #101 on: January 22, 2025, 10:45:54 am »
EEVBlog Forum, The Place to discuss your adventures with with real panda manure ad ∞
 

Offline magic

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Re: Warning- LM317K duds from Digikey
« Reply #102 on: January 22, 2025, 10:56:12 am »
Wait, it's a shit circuit? I thought you kept saying I hadn't provided enough info on the circuit? Interesting.
You did provide some information: the factory installed voltage regulator failed.
But it's not enough information to know for sure that the new one is crap.

You claim that something is junk, people ask questions. Surprising, isn't it?
 
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Online bdunham7

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Re: Warning- LM317K duds from Digikey
« Reply #103 on: January 22, 2025, 05:07:37 pm »
But I'm curious what exactly went wrong and not accepting hand wavy non-explanations for this reason.

It seems pretty clear to me that the primary issue is the bond wires.  The regulator has current limiting so unless that is bogus as well, the only way the circuit could cause an overcurrent is by reverse biasing it.  And since he tested them separately with a DC load, even if the current limiting was bogus or he hooked them up backwards, the current was externally limited and shouldn't have blown the wires off.

Bogus (meaning they don't work to spec) LM317 series regulators are legion these days so the only suprise here is that you can get them from Digi-Key directly instead through their Marketplace portal where most of the fake stuff is. 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Offline magic

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Re: Warning- LM317K duds from Digikey
« Reply #104 on: January 22, 2025, 05:17:16 pm »
One more thing I could imagine is the positive rail going negative if the negative rail came up first and then overvoltage, breakdown and overcurrent.

But realistically, the wimpy wires are the most likely culprit indeed. And of course, if their datashit is to be believed, the chip is capable of sourcing more current than it can survive ;)

But again, realistically, the wires fuse at 0.5A, the chip smokes at 1A, the spec says 1.5A and somebody inevitably sells it as a 5A part on eBay.
« Last Edit: January 22, 2025, 05:20:20 pm by magic »
 

Offline floobydust

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Re: Warning- LM317K duds from Digikey
« Reply #105 on: January 22, 2025, 05:48:51 pm »
One more thing I could imagine is the positive rail going negative if the negative rail came up first and then overvoltage, breakdown and overcurrent.

But realistically, the wimpy wires are the most likely culprit indeed. And of course, if their datashit is to be believed, the chip is capable of sourcing more current than it can survive ;)

But again, realistically, the wires fuse at 0.5A, the chip smokes at 1A, the spec says 1.5A and somebody inevitably sells it as a 5A part on eBay.

'317 does not have a ground pin, if the IC fails there is no overcurrent other than it what it can push into the load by overvoltaging it. The ADJ pin resistor limits that.
But... in a bench power supply the ADJ pin potentiometer smokes (add a polyfuse) when you dial it down wondering why the output voltage is too high. Then, when you short the output, the IC finally melts.


EVVO Semiconductor screwed up twice - defective packaging, and defective test. No biggie in china, this is par for the course.
Do they have an independently-audited quality system in place?
Shame on Digi-Key for letting anyone into their supply. For all that markup of theirs, they have no vetting process it appears.
LM317K TI is $1.00 on LCSC verses $6.61 from EVVO on DK.
 

Online wraper

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Re: Warning- LM317K duds from Digikey
« Reply #106 on: January 22, 2025, 06:14:00 pm »
LM317K TI is $1.00 on LCSC verses $6.61 from EVVO on DK.
Those are not TO-3 317K but plastic packages at LCSC.
 

Offline floobydust

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Re: Warning- LM317K duds from Digikey
« Reply #107 on: January 22, 2025, 06:40:54 pm »
OK I must be too hasty, in my day the "K" was TO-3, and "T" suffix TO-220 but it means nothing now. I'd found it as a TI "TO-3-2" I think but now the listings price is up there past $40 ea.
Aliexpress N/S LM317K TO-3 $1.52 for two or $3.79 for five. Ask for lucky one. Well, it's not the steel costs I guess.
/s You could just buy some TO-3's and cut off the top to do your own QA. Then tack solder a real TO-220 or D2PAK in there, and have something better. It's that ridiculous.
 

Online bdunham7

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Re: Warning- LM317K duds from Digikey
« Reply #108 on: January 22, 2025, 07:08:47 pm »
You could just buy some TO-3's and cut off the top to do your own QA. Then tack solder a real TO-220 or D2PAK in there, and have something better. It's that ridiculous.

Perhaps an improved version of this? 

https://www.ebay.com/itm/266761106914
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline floobydust

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Re: Warning- LM317K duds from Digikey
« Reply #109 on: January 22, 2025, 07:57:02 pm »
Looks reasonable but a bit expensive. In the old days it was common to see a TO-3 voltage reg on a small tiny heatsink, so a few watts at best dissipation, which by today's standards was a huge waste of metal.
I'm just postulating where the markup truly is for these parts. Not the TO-3 can, not the die. You have to wonder.

Many "semiconductor" vendors are buying the dies and just do their own packaging of them. That is their core business.
 

Online wraper

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Re: Warning- LM317K duds from Digikey
« Reply #110 on: January 22, 2025, 08:06:33 pm »
You could just buy some TO-3's and cut off the top to do your own QA. Then tack solder a real TO-220 or D2PAK in there, and have something better. It's that ridiculous.

Perhaps an improved version of this? 

https://www.ebay.com/itm/266761106914
You'd be way better off with TO-220 package + 2 wires. Thermal conductivity is simply not there as it's just a usual 2 layer PCB with vias. So unless component is lightly loaded, this thing is pretty much worthless.
 

Offline floobydust

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Re: Warning- LM317K duds from Digikey
« Reply #111 on: January 22, 2025, 08:31:50 pm »
I remember the TO-220 form factor sizing was to replace the TO-66. You can bolt one in place there but can't remember trying it.
 

Online bdunham7

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Re: Warning- LM317K duds from Digikey
« Reply #112 on: January 22, 2025, 08:32:20 pm »
You'd be way better off with TO-220 package + 2 wires. Thermal conductivity is simply not there as it's just a usual 2 layer PCB with vias. So unless component is lightly loaded, this thing is pretty much worthless.

That was why I suggested an improved version.  Perhaps a machined copper insert and low-temp solder for the center pad?  IDK how good you could get it with 4-layer 2oz copper and vias everywhere possible.  I've done TO-220 retrofits and I've never been happy with the way the look--often TO-3 devices are filling holes in a chassis. 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline floobydust

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Re: Warning- LM317K duds from Digikey
« Reply #113 on: January 22, 2025, 08:43:05 pm »
With the TO-3 (TO-204) obsolete it will become more of an issue for replacement.
The automotive industry is using thermal adhesive under the PC board, that also flows into the vias, to transfer heat from semi's to the die-cast enclosure in ECU's. It's proven to work but I'm not a glue fan really.
I thought the LM317 is not high power, dissipation max. 20W compared to power transistors in the same package.

 

Online wraper

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Re: Warning- LM317K duds from Digikey
« Reply #114 on: January 22, 2025, 09:08:30 pm »
You'd be way better off with TO-220 package + 2 wires. Thermal conductivity is simply not there as it's just a usual 2 layer PCB with vias. So unless component is lightly loaded, this thing is pretty much worthless.

That was why I suggested an improved version.  Perhaps a machined copper insert and low-temp solder for the center pad?  IDK how good you could get it with 4-layer 2oz copper and vias everywhere possible.  I've done TO-220 retrofits and I've never been happy with the way the look--often TO-3 devices are filling holes in a chassis.
I already suggested PCB of half TO-3 footprint + TO-220. No temperature compromise. But it's just unneeded bells and whistles. You can nicely fit TO-220 screwed to one of the holes + 2 wires soldered directly to IC terminals as their order is the same as on TO3 if fit like on the sketch I posted.
 

Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #115 on: January 22, 2025, 10:35:08 pm »

But I'm curious what exactly went wrong and not accepting hand wavy non-explanations for this reason.

You're "not accepting" certain responses? You really are an authority of some sort in your own mind aren't you? :-DD


P.S. Enough with the post edits after replies, I keep having to go back to shitposts of yours I've already replied to after you change them

...
One more thing I could imagine is the positive rail going negative if the negative rail came up first and then overvoltage, breakdown and overcurrent.
...

You've shown that you can imagine a lot of things, regardless of their basis in reality.

...
But realistically, the wimpy wires are the most likely culprit indeed.
...

OK cool, see you again in your next post where we go back to the conspiracy theories :-//
 

Online thm_w

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Re: Warning- LM317K duds from Digikey
« Reply #116 on: January 22, 2025, 11:02:38 pm »
Shorted the output, raised current to 2A, didn't even see 1.5A on the display and the bond wire had blown open. Vin was 6V, and happened so fast, so no issue with die temperature.

I don't have proper calipers here but wire is ~0.04mm.
Managed to get it to glow red at only 1A with careful probing. So aluminum could make sense.

Bonding looks rough too:


Same batch/date code (mine were all 2437)?

Yes same batch.
I'll ask digikey for refund.
« Last Edit: January 22, 2025, 11:10:26 pm by thm_w »
Profile -> Modify profile -> Look and Layout ->  Don't show users' signatures
 
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Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #117 on: January 22, 2025, 11:23:06 pm »
Shorted the output, raised current to 2A, didn't even see 1.5A on the display and the bond wire had blown open. Vin was 6V, and happened so fast, so no issue with die temperature.

I don't have proper calipers here but wire is ~0.04mm.
Managed to get it to glow red at only 1A with careful probing. So aluminum could make sense.

Bonding looks rough too:
(Attachment Link)

Same batch/date code (mine were all 2437)?

Yes same batch.
I'll ask digikey for refund.

Thanks for putting in the effort to confirm!
 

Offline magic

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Re: Warning- LM317K duds from Digikey
« Reply #118 on: January 22, 2025, 11:53:01 pm »
Shorted the output, raised current to 2A, didn't even see 1.5A on the display and the bond wire had blown open.
OK, but can you be certain that 1.5A was not actually reached, even transiently?
Remember, this is the absolute maximum rating of the part you bought, and internal current limit is suggested to be higher and certainly not guaranteed to be lower.

If I were DigiKey I would reject your refund :P
 

Online thm_w

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Re: Warning- LM317K duds from Digikey
« Reply #119 on: January 23, 2025, 12:09:54 am »
OK, but can you be certain that 1.5A was not actually reached, even transiently?
Remember, this is the absolute maximum rating of the part you bought, and internal current limit is suggested to be higher and certainly not guaranteed to be lower.

Read the post again please, and count the number of bond wires seen in the photo.
1 for Vin, 1 for Adj, 2 for Vout
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Offline magic

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Re: Warning- LM317K duds from Digikey
« Reply #120 on: January 23, 2025, 09:20:56 am »
Yes, Vout is Kelvin sensed.

OK, you got it to glow red at 1A, fair enough I guess. Not sure how I missed it first time.
« Last Edit: January 23, 2025, 09:26:12 am by magic »
 
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Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #121 on: January 23, 2025, 10:23:09 am »
...
Not sure how I missed it first time.
...

Maybe because you've spent 5 pages shit stirring and the signal to noise ratio in this thread at this point is completely cooked?

Yeah. Might be that I reckon.
 
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Offline magic

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Re: Warning- LM317K duds from Digikey
« Reply #122 on: January 23, 2025, 10:54:51 am »
Quote
5 pages

I think you have confused me with 10 quadrillion other people who also doubted your competence, but appear to be convinced by thm_w's post at last, for some reason.
 
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Online bdunham7

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Re: Warning- LM317K duds from Digikey
« Reply #123 on: January 23, 2025, 03:02:30 pm »
I don't have proper calipers here but wire is ~0.04mm.
Managed to get it to glow red at only 1A with careful probing. So aluminum could make sense.

Aluminum melts before it glows.

0.04mm is ~1.5mils, that would be good enough for about 0.5A in free air if it were gold.

https://www.renesas.com/en/document/atc/power-systems-design-estimating-bond-wire-current-carrying-capacity?srsltid=AfmBOoqrX5L5AJugpkSg_Ak_EBoo_f-i2Y7UH1AhLFXev6J48zieFkpR
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Offline magic

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Re: Warning- LM317K duds from Digikey
« Reply #124 on: January 23, 2025, 03:56:50 pm »
Aluminium melts above 600°C and in darkness you should be able to see a faint glow at this kind of temperature.
 


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