Author Topic: Warning- LM317K duds from Digikey  (Read 9493 times)

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Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #50 on: January 11, 2025, 01:08:08 pm »
iSC
 

Online wraper

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Re: Warning- LM317K duds from Digikey
« Reply #51 on: January 11, 2025, 01:08:20 pm »
Personally I avoid the Multicomp and RS-pro branded parts from Farnell and RS as these are rather crappy. I can buy better quality from Aliexpress.
They are YMMV, not crappy. Often you can figure out their origin from the datasheets. For example I bought cheap Multicomp 3D printer filament that was eSun in disguise, and I figured it out before the purchase. Sometimes you can find top tier parts in disguise. You can get better quality Aliexpress, although your chances of that are very slim.
 

Offline magic

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Re: Warning- LM317K duds from Digikey
« Reply #52 on: January 11, 2025, 01:11:11 pm »
As expected, you blew the input fuse.
 
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Online wraper

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Re: Warning- LM317K duds from Digikey
« Reply #53 on: January 11, 2025, 01:14:59 pm »
iSC
Construction looks fine. Presence of the heat spreader under the die indicates they did not save every penny. Bottom of the barrel parts usually do not have it.
« Last Edit: January 11, 2025, 01:18:48 pm by wraper »
 

Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #54 on: January 11, 2025, 01:16:43 pm »
As expected, you blew the input fuse.

To be fair, I was pretty rough opening them so it's possible any high impedance air gaps were generated in the vice ;D

I'll crack open the other two EVVOs later on and see if there's much difference
 

Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #55 on: January 11, 2025, 01:17:46 pm »
iSC
Construction looks fine. Presence of the heat spreader under the die indicates they did not save every penny. Bottom of the barrel parts usually do not have it.

These are NOT the dud parts from Digikey, these are the ones I got later that work fine. But it looks like the parts you've been defending don't have it. Interesting...
 
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Online wraper

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Re: Warning- LM317K duds from Digikey
« Reply #56 on: January 11, 2025, 01:28:46 pm »
iSC
Construction looks fine. Presence of the heat spreader under the die indicates they did not save every penny. Bottom of the barrel parts usually do not have it.

These are NOT the dud parts from Digikey, these are the ones I got later that work fine. But it looks like the parts you've been defending don't have it. Interesting...
I was not defending it. I was asking for more info to make an informed opinion. As of EVVO part I did not notice on previous page, die size looks ok. Bond wires are somewhat thin but probably enough for rated current. Bonding to the package looks to be some transparent glue which is not good. Lack of heat spreader, it may be ok if the package has thick bottom, otherwise not good. Certainly not worth $10, I'd use $ 0.30 TO-220 part instead even if I had to pay $10 for it.
« Last Edit: January 11, 2025, 01:32:40 pm by wraper »
 

Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #57 on: January 11, 2025, 01:46:09 pm »
iSC
Construction looks fine. Presence of the heat spreader under the die indicates they did not save every penny. Bottom of the barrel parts usually do not have it.

These are NOT the dud parts from Digikey, these are the ones I got later that work fine. But it looks like the parts you've been defending don't have it. Interesting...
I was not defending it. I was asking for more info to make an informed opinion. As of EVVO part I did not notice on previous page, die size looks ok. Bond wires are somewhat thin but probably enough for rated current. Bonding to the package looks to be some transparent glue which is not good. Lack of heat spreader, it may be ok if the package has thick bottom, otherwise not good. Certainly not worth $10, I'd use $ 0.30 TO-220 part instead even if I had to pay $10 for it.

So we spent 3 pages to get your "expert" conclusion that it's a shitty part. Which I had already deduced from testing before my first post about it. Fantastic. You're my hero.
 
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Online wraper

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Re: Warning- LM317K duds from Digikey
« Reply #58 on: January 11, 2025, 02:12:20 pm »
Interesting, found exactly the same die in some unknown 'LM338K' https://zeptobars.com/en/read/LM338K-5A-LDO-TO-3-TO-220
 
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Offline magic

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Re: Warning- LM317K duds from Digikey
« Reply #59 on: January 11, 2025, 03:09:48 pm »
That's a Darlington output so it isn't a 1117, they just copy-pasted wrong schematic into their datashit.

And somebody even upgraded it to 5A, nice ;)
« Last Edit: January 11, 2025, 03:11:58 pm by magic »
 

Online bdunham7

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Re: Warning- LM317K duds from Digikey
« Reply #60 on: January 11, 2025, 04:40:44 pm »
Alright, I got curious and peeled some regulators open. The ST one is the original dead one, there's one of the dead EVVO ones and then I sacrificed a working iSC one for more comparison options. I have limited zoom and even more limited knowledge of what I'm looking for here, but the things that stuck out to me are all three dies have "317" written on them (which I would assume rules out a simple silkscreening lie on the cases) and the ST/iSC ones have a significant raised section of the case under the dies whereas the EVVO one is dead flat. Not sure if that has much effect on the thermal side of things?

Nice pictures!  Unless I'm blind, there's no die damage on the EVVO part and there doesn't seem to be any obvious chicanery with the die size or type.  So perhaps it is just a thrifted (but not "fake") part that happens to have a defect that happened somewhere in the manufacturing process.  IDK how much the heat spreader matters because an LM317K isn't intended to dissipate hundreds of watts like a 2N3055 or some of the even larger power transistors.  In any case, even if the part were thermally insufficient it shouldn't have completely failed.  b/t/w, did it fail open or short? 
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 David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #61 on: January 12, 2025, 02:34:48 am »
Alright, I got curious and peeled some regulators open. The ST one is the original dead one, there's one of the dead EVVO ones and then I sacrificed a working iSC one for more comparison options. I have limited zoom and even more limited knowledge of what I'm looking for here, but the things that stuck out to me are all three dies have "317" written on them (which I would assume rules out a simple silkscreening lie on the cases) and the ST/iSC ones have a significant raised section of the case under the dies whereas the EVVO one is dead flat. Not sure if that has much effect on the thermal side of things?

Nice pictures!  Unless I'm blind, there's no die damage on the EVVO part and there doesn't seem to be any obvious chicanery with the die size or type.  So perhaps it is just a thrifted (but not "fake") part that happens to have a defect that happened somewhere in the manufacturing process.  IDK how much the heat spreader matters because an LM317K isn't intended to dissipate hundreds of watts like a 2N3055 or some of the even larger power transistors.  In any case, even if the part were thermally insufficient it shouldn't have completely failed.  b/t/w, did it fail open or short?

I'll upload pictures later, but I cut open the second one and that one had some residue that looked like something had popped violently. Haven't opened the third yet. Will double check connections between pins when I do that and update
 

Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #62 on: January 14, 2025, 12:52:05 am »
Pics of the other 2 failed units incoming. On both of these it looks a lot more obvious that the bond wires vaporised

Also, the manufacturer has now gotten back to me about questions I had sent them. They say it's not a new product to their line and while it wasn't up on the English version of their site it is there on the Chinese version, so it hasn't been pulled from production or anything like that.
 
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Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #63 on: January 14, 2025, 12:52:39 am »
Third unit
 

Online bdunham7

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Re: Warning- LM317K duds from Digikey
« Reply #64 on: January 14, 2025, 03:45:48 am »
Pics of the other 2 failed units incoming. On both of these it looks a lot more obvious that the bond wires vaporised

CCA bond wires??   :-DD

Is there any way you can measure the thickness of those bond wires?
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.
 

Online wraper

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Re: Warning- LM317K duds from Digikey
« Reply #65 on: January 14, 2025, 04:01:40 am »
Pics of the other 2 failed units incoming. On both of these it looks a lot more obvious that the bond wires vaporised

CCA bond wires??   :-DD

Is there any way you can measure the thickness of those bond wires?
Aluminum bond wire is normal and AFAIK is a primary choice if not using much more expensive gold. Other ICs seem to use aluminum too. However others seem to have thicker wires and a pair of them from in/out. Die in EVVO IC also has a place for a pair of bond wires but there is only one bonded. Also input bond wire is very long in comparison which makes it heat more.
« Last Edit: January 14, 2025, 04:09:39 am by wraper »
 

Offline KE5FX

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Re: Warning- LM317K duds from Digikey
« Reply #66 on: January 14, 2025, 06:45:52 am »
Not trying to defend the shady parts, but I assume you've checked the capacitance and/or ESR of the bulk cap(s) upstream of the regulator?  If there's more (good) capacitance downstream than upstream, and no reverse-bias protection diode is present, that could explain both the original regulator failure and the new ones.  They could be taking some damage at power-off time that curtails their operating life drastically...
 

Offline Psi

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Re: Warning- LM317K duds from Digikey
« Reply #67 on: January 14, 2025, 07:05:32 am »
Not sure how practical this is for you, but if you have a microscope it would be interesting to touch a ultra pointed probe on one of the intact bond wires at the die and push 1A through it from CC psu to one of the output terminals while accuracy measuring uV/mV across it using 2nd meter so you can calc resistance.

« Last Edit: January 14, 2025, 07:07:12 am by Psi »
Greek letter 'Psi' (not Pounds per Square Inch)
 
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Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #68 on: January 14, 2025, 08:23:54 am »
Pics of the other 2 failed units incoming. On both of these it looks a lot more obvious that the bond wires vaporised

CCA bond wires??   :-DD

Is there any way you can measure the thickness of those bond wires?

Probably not anywhere near accurately unfortunately  :(
 

Offline Ice-Tea

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Re: Warning- LM317K duds from Digikey
« Reply #69 on: January 14, 2025, 08:25:45 am »
Is it just me or is the workmanship on these bond wire pretty bad?
 

Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #70 on: January 14, 2025, 08:35:20 am »
Not trying to defend the shady parts, but I assume you've checked the capacitance and/or ESR of the bulk cap(s) upstream of the regulator?  If there's more (good) capacitance downstream than upstream, and no reverse-bias protection diode is present, that could explain both the original regulator failure and the new ones.  They could be taking some damage at power-off time that curtails their operating life drastically...

All of these questions have been covered many times in this thread now, but given that it got unnecessarily derailed for a couple pages I'll recap again to save you sifting through:
- The original regulator failed due to the owner of the unit poking around inside and apparently shorting something out. These new EVVO regulators failed but the newer ones of a different brand have worked just fine
- All power supply components had already been tested and confirmed working. Protection diodes ARE present
- These regulators not only failed while powering the unit, but also when the power supply was only driving a DC load which rules out all other circuitry in the unit
- They didn't even last long enough to be powered down once so definitely couldn't have copped that kind of damage. The first one failed at power up, and it was confirmed on the other two that any load exceeding about 1A would kill them instantly (the actual load is something like 1.2A from memory so it makes sense why the first one died while powering on the unit). On that note, I can't remember if I mentioned it originally but just to state the obvious, the supply WAS checked and working before connecting to the unit, just not heavily load tested as I had no reason to think these couldn't provide the rated current and I'd already confirmed the rest of the unit powered up OK with a bench supply
 

Offline David AuroraTopic starter

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Re: Warning- LM317K duds from Digikey
« Reply #71 on: January 14, 2025, 08:40:27 am »
Not sure how practical this is for you, but if you have a microscope it would be interesting to touch a ultra pointed probe on one of the intact bond wires at the die and push 1A through it from CC psu to one of the output terminals while accuracy measuring uV/mV across it using 2nd meter so you can calc resistance.

That would definitely be interesting! Might be a bit more effort than I want to throw at it at this point though, plus I don't know how much faith we can realistically place on the remaining bond wires. I feel like it's anyones guess whether they were also compromised during failure or if they'd still be in the same shape they left the factory in
 

Offline floobydust

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Re: Warning- LM317K duds from Digikey
« Reply #72 on: January 14, 2025, 06:37:57 pm »
Those fused bonding wires look too skinny. The ADJ teminal I could see a thinner gauge possible but whoever packaged the part seems to have saved a millipenny.
I wonder the die size if they shrunk it too much or it's also for 150mA versions etc . and they zap current-sense resistors to set that?
I don't see a heat spreader either.
 
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Offline mikerj

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Re: Warning- LM317K duds from Digikey
« Reply #73 on: January 16, 2025, 10:25:33 pm »
Might be worth sending the pics to Digikey so they can get an idea of the shoddy crap they are selling.
 

Offline mikerj

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Re: Warning- LM317K duds from Digikey
« Reply #74 on: January 17, 2025, 03:26:42 pm »
looks different to me  :-//

This was never in question.  All three dies are different.
 


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