some news from the "magic smoke club"

madias
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some news from the "magic smoke club"

Postby madias » Tue Jul 19, 2016 8:27 pm

Meanwhile I burned about 3 minis (all BAITE models), but the good news: All of them are working again :)
I suspected in a thread some months ago that the AMS1117 (3.3) voltage regulator is a counterfeit and this is the problem. I'm not sure about it, because I soldered on every "smoked candidate" a new one I ordered separately (100PCS roll for about...some less Euros, can't remember).
My new "victim" is the protecting diode sitting next to the AMS1117: If I power the mini from a external power source (7-9V) and using about 150-400mAh (should be save within specs) from the 3.3V lines the diode will get hot and up in smoke after a while. So I suspect this little thing is totally undersized or trash. Sadly the diode is in a bad place to exchange especially when the pin rows are already soldered. A shortcut is possible, with a *big* warning: NEVER use USB and external power together (especially if the external power is over 5V) otherwise you can say goodbye to your USB hub (If your are a smart guy (I always use an USB hub between MCU's and PC/laptop)) or to your laptop/PC USB port. In other words: Shortcut the burned diode to test if the mini is alive and then replace it with a "real" diode, because I'm sure that nobody will remember that "mod" after a few months.

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martinayotte
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Re: some news from the "magic smoke club"

Postby martinayotte » Tue Jul 19, 2016 9:03 pm

I've got one of those schottky diodes into smoke by accidentally shorting the power on a breadboard. In the same period, Andy did the same.
We both purchase lot of 50 or 100 on eBay for $0.99 ...

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ahull
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Re: some news from the "magic smoke club"

Postby ahull » Tue Jul 19, 2016 9:08 pm

These.. http://www.ebay.co.uk/itm/STM32F103C8T6 ... SwanRXg5Qn

Look easier to "unsmoke" in that they have a larger PCB, all be it that they cost a little more. They also have all of the pin legends on the back, so a good reference board.

I added a Victor 921 multmeter to my PCB graveyard, at least temporarily. In the course of my surgery to see if I can get a serial output from it, on it I've lost one of the rotary switch contacts, so not actually smoked, more sort of sent the offending part in to some other dimension. I've checked everywhere. I'll need to fabricate a replacement out of copper tape, with the scalpel.

Meantime, I've carefully put it all back together, no doubt when I get back to it, some other small part will have escaped in to the twighlight zone.

On the plus side, a lot of these things are so cheap, that smoking them is more damaging to the ego than the wallet. The little multimeter may be cheap junk, but it is theoretically capable of 14bit 6000 count results and RS232, so at £7.66 I can afford another one if I kill it. I would be crying in my beer if I blew up the Fluke.

Oh well, you can't make an omelette without burning a few eggs... at least that's what I tell my wife... maybe that's why she doesn't let me in the kitchen anymore... that and soldering with lead solder on top of the cooker of course. :twisted:

On the plus side of the balance sheet, I recently "unsmoked" a couple of laser printers, an ultrasonic cleaner and a Kenwood Chef food mixer speed controller, so I'm in danger of being drummed out of the club for fixing more than I blow up. :?
- Andy Hull -

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Pito
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Re: some news from the "magic smoke club"

Postby Pito » Wed Jul 20, 2016 10:54 am

Any idea what part is the diode?
The power dissipation does not seem to be so high..
Si diodes power.JPG
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ahull
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Re: some news from the "magic smoke club"

Postby ahull » Thu Aug 04, 2016 11:07 am

ahull wrote:...
I added a Victor 921 multmeter to my PCB graveyard, at least temporarily. In the course of my surgery to see if I can get a serial output from it, on it I've lost one of the rotary switch contacts, so not actually smoked, more sort of sent the offending part in to some other dimension. I've checked everywhere. I'll need to fabricate a replacement out of copper tape, with the scalpel.
...


Just a quick follow up on this remark. You can indeed get serial output from the Victor VC-921 and also convert it to 6000 or 8000 counts.
More details here.. viewtopic.php?f=45&t=1296&p=16704#p16704
- Andy Hull -


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