DIY-More 'Strong' query

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Phil_G
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DIY-More 'Strong' query

Post by Phil_G »

Can anyone else please confirm if they've witnessed the following with a new DIY-More Strong board?
Its a bit of a story, bear with me:

A while back I had a call from Stu who said that on full rotation of the rates pot, the encoder shut down, and rebooted when the pot was turned back to minimum rates.
This was the first and I assumed he'd wired the pot wrongly or somehow grounded A7 (rates) so when the pot was turned to full (+5v) it shorted the 5v supply. I swapped his encoder but asked him to return the faulty one. I tested it and sure enough A7 signal pin was fully grounded, with nothing plugged in. There were no visible shorts under the microscope. Anyway Stu was happy with his replacement so it went in the bin.

Couple of weeks later I was making one of my homebrew FHSS sets and whilst it worked fine, when I tried almost full rates the rates, there was a burning smell and the pot track burnt. I unplugged everything and sure enough A7 was fully grounded.

Knowing now that it wasnt a mistake or a one-off, I pulled my stash of 40+ unopened, fresh from China DIY-More Strong boards. Testing A7 to ground on every board I found three had the problem, a dead short to ground. This is before any assembly or mods, straight from the packet.

So under the microscope I traced the A7 pin to the processor chip. This track ducks under the regulator which I removed for clarity, then it swaps sides a couple of times and comes up a through-hole under the 328P. Its the one feed on the whole chip that isnt visible, its taken under the chip to pin 22. I isolated this pin and the fault remained, so it looks like a (possibly microscopic) etching or THP problem on a few random boards, or since A7 is next to a ground pin maybe its solder paste spread during OEM assembly.

This has only ever happened on A7 and other than rates the faulty board performs perfectly. My suggestion is, before starting any work on a new DIY-More Strong board, test A0-A7 to ground using the lowest resistance range of your DMM. If the board is faulty, its a full short so its very obvious when testing. Any encoders I send out will have been tested ok of course.

Has anyone else come across this specific problem on the DIY-More ProMini Strong board?
I should add that in several hundred Strong boards, none have failed in service, it seems to be purely a 'DOA' manufacturing problem on a small percentage of boards.

Cheers
Phil
RichardT
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Joined: 03 Mar 2019, 17:15
Location: Surrey

Re: DIY-More 'Strong' query

Post by RichardT »

I've just tested the half dozen DIY-More Strong boards that I have and they're all ok

Hopefully it's an intermittent manufacturing fault but as you suggest it's best to test every board

Cheers - Richard
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Mike_K
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Joined: 16 Feb 2018, 06:35
Location: Hertfordshire

Re: DIY-More 'Strong' query

Post by Mike_K »

Hi Phil

I usually use standard Nano, but tested the five I have and all tested OK, but probably not enough to statistically get a failure.

Mike
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Mike_K
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Joined: 16 Feb 2018, 06:35
Location: Hertfordshire

Re: DIY-More 'Strong' query

Post by Mike_K »

More bad news to report on the DM DIY MORE Pro Mini Strong boards.

I bought 10 directly from their official website and have had 4 out of 10 with problems on the analogue input pins being shorted to ground. And rather than Phil's problem where it was only A7, these have been random pins, A1 on one A4 another and A7 on two. So do I trust the other boards now? Well, they are getting a very thorough "burn-in" period, which should hopefully prove if they are OK or not.

Cheers Mike
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