Yes 5v and gnd. Dont go higher than 5.5V or put in a low current limit, i think i already destroyed something by going up to 6V.
I just checked with another multimeter and this one is useless like yours (only goes up to 2V)
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Alrighty - I just tried that test. When I put the power supply across the input in the “wrong” direction, I get about .05 mA at pretty much any voltage. When the voltage goes a bit over 2.5 the current jumps to about 0.3mA. So I’m guessing a proper meter would show me a reverse bias around 2.5V - right?
As one would readily guess, I’m not an EE. Strictly a hobbyist. I appreciate the patience.
And I would take this off-line except it seems there’s at least one other person with these same questions.
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@Fungineers was able to fix the DRV issue by reflowing his chip, so that makes me think the problem (hopefully) might not be with the DRVs themselves. Maybe a component near the DRV? Just my thoughts – hopefully it’s an easy fix.
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Yes, i hope thats the case too. Maybe the vsense voltage divider? I will check everything thats connected to the buck converter tomorrow.
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I wonder also what the output (faulty) regulated voltage waveform looks like… If it indeed is rippling or fluctuating then it could lend some insight to a buck converter issue + could be related to the audible noise. Might be worth trying to scope it out.
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Waveforms always tell a good story on what’s going on. Wish I had one of these faulty units to analyze myself… But yeah audible ringing in the inductor screams bad feedback/regulation for the buck converter. Maybe one of the feedback components are not soldered well or something (see circled)
If this turns out to be inadequate soldering of a component from JLCPCB then I might know why. Has to do with thermal reliefs (or lack thereof) on the top copper layer. I’ll put in thermal reliefs either way for v1.0.
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Thank you shaman.
Well i got some bad news, i checked all the external components of the buck converter and they dont seem to be the cause for the malfunction. I even unsoldered a few components and checked them externally (C14, D6). Everything is pointing to the DRV chip.
I then switched the DRV from a known bad Focer to one of the good focers of Batch 1 and this confirmed a bad DRV chip.
Also confirmend the amount of bad Focers from the Group Bay Batch 2 to 25/60pcs 
I now ordered 20 new DRV8301 from china but this will take at least 1 month to arrive.
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This is unfortunate and troubling. I say you have enough evidence to bring to JLCPCB for a complaint and request for a refund.
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Low quality DRVs perhaps?
I once bought a bunch of cheap DRV8302 from ebay. Those chips never worked out for me. (5V was always ok though)
After that I bought from Mouser Instead. Since then all my DRV repairs have been successful
I don’t trust the cheaper ebay DRVs. Threw them all away 
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Dumb question #1704:
I thought thermal reliefs were only needed for hand soldering - no?
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They help prevent “tombstoning” during the reflow soldering process in SMT assembly. This is where The pads of a resistor or capacitor heat unevenly and causes them to get pulled upright by the pad that flows first. Could also just result one pad being soldered and the other one being a cold joint.
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Thanks. I’m aware of tomb-stoning, but never really thought about the cause. I guess I had imagined either a poorly placed part or a bad job with the solder stencil.
The more you know…
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I have just tested my batch of 10 units. 8 seems good, 2 seems bad. But all of them are without FETs and remaining components as I am still waiting them. I used 10k resistor and gave around 4V with power supply with current limited at 10mA. I then used multimeter to measure voltage on POS and NEG. Most of them gave ~2.49V, but two were 2.99V. I used this method as I do not have proper diode tester.
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I’ve got similar results with the 4 partially assembled ones I have on hand right now. One of the 4 is at 2.9ish while the other 3 where around 2.5-2.6 (can’t remember the exact value). The boards are all at various stages of completion so I don’t think the extra few components change the values drastically.
If these are indeed faulty DRV’s would JLCPCB be refunding/supplying new components? Not to sure how the customer service in this industry works!
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It will take some considerable proof to say these are faulty units even though it seems obvious to us. @doomy’s findings and waveforms might be enough to convince the first level customer support for a quick and easy refund. Otherwise we’ll have to go deeper.
Thankfully each DRV has a lot code on it…and that can be traced. Say those lot codes correspond to a lot that was trashed by TI due to low yield. Say that lot ended up in the grey market electronics distribution pool (LCSC/JLCPCB). If that’s the case, then we have something.
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Awesome thanks for the insight I figured it might be a little more complex than your standard AliExpress type refund.
I’ll make sure when I get home to test all my units to get back some solid numbers. The more people testing the better!
From what I understand the PCB’s are all tested before shipping (at least from what I remember when I ordered mine that was an option) but I’m not sure if they’re just testing to make sure that all the solder joints are good or what the procedure is.
Seems weird that the issue seems to follow the DRV from one board to another.
And intersecting I was not aware that lcsc/jlcpcb is considered grey market, or that there was even a such a thing but it makes sense.
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yes. They undergo a flying probe test but that applies to only the PCB itself.
They’re not a licensed distributor for most of the name brand stuff they sell. The licenses they have are mostly for Asian IC brands…yet you still see ST, TI, ADI, ect in their stock. They’re also able to sell these name brand ICs for stupid cheap at low quantity.
I haven’t personally had an issue with this and all business I’ve done with them so far has been good. These recent issues are something new and something I haven’t personally experienced.
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Ahh okay good to know thanks for clarifying! And also makes sense why they’d be a little more likely to get a bad batch of DRV’s compared to a licensed distributor!
Of the 10 boards I ordered it appears that 3 of them are faulty while the rest are fine. Visually they all appear fine as far as I can tell, would having a faulty one on hand allow you to get to the bottom of this any quicker/ easier?
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for anyone looking for a single enclosure: https://drive.google.com/drive/folders/1v_Hg4pyX2-QMUf1HvZjGG4pvR7jflopF?usp=sharing
like $12CAD from Digikey + thermal pads (.5mm)
(also I haven’t blown anything up in over 40! minutes of riding!)
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