When I attach a USB cable the board doesn’t power up. I checked the cable and USB supply, both OK.
With the USB cable attached (into a powered hub at the other end) I measured 0V out of the lm1117 regulator. Looking at the schematic I guessed it was worth trying applying 5V to VIN. Frankly I don’t quite understand the dual-transistor circuit connected to PB9, so tried VIN first, which worked. Everything seemed to be functioning, I just can’t power the board from USB anymore.
Not a big issue since 5V for VIN, or 3.3V for VCC are both available on my desk, and when I finally get around to putting this into a project, I won’t be powering from the USB jack anyway, just kinda sucks I damaged it.
I measured the D2 diode, very high resistance in both directions. Could I remove the diode and replace with a solder connection (I don’t have any S4 diodes), but would that put my USB port at risk? If I never use both VIN and USBVCC would I be ok (just living with the risk of damaging my computer or hub USB port)? What purpose does the diode serve?
Can you tell I’ve never really done this before?
Thanks.

Yes, Andy and myself purchased some of those S4 after our Magic Smoke club experiences, they are pretty cheap.
http://m.aliexpress.com/item/32541620627.html
Thanks for all the info!
I think I’ll get a late Christmas present, something to add light and magnification.
http://cpc.farnell.com/linear-tools/59- … dp/PY31675
£11 — £13 ukp
i’ve also a set of the spectacle type, tried them on, un-used since.
i use the second, but i also have ‘reading’ glasses of 2.00 and 3.00 which combined the above means i need to be careful of the soldering irons’ hot barrel.
stephen
http://cpc.farnell.com/linear-tools/59- … dp/PY31675
£11 — £13 ukp
i’ve also a set of the spectacle type, tried them on, un-used since.
i use the second, but i also have ‘reading’ glasses of 2.00 and 3.00 which combined the above means i need to be careful of the soldering irons’ hot barrel.
stephen
do you ever think must find the dremel and convert these lens to bi-focal or is it the 6x you’re after?
as i’m normally at 2x for the laptop, for the kindle & bread boarding i need the x3 and for smd the band as well with it ‘s range of magnification.
don’t know if you can, have a look at january nuts & volts p55 fig 2 is what i thought you could use to calc/estimate when to shut off
stephen
do you ever think must find the dremel and convert these lens to bi-focal or is it the 6x you’re after?
battery loses it.
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