Teensy 4.1 USB Connection Problem

A

Akram

New member
Hi,
I had brought 5 teensy boards and every one of them worked fine except for one.
When i connect the faulty board to pc, it does not even show up in device manager. I know that my USB cable is fine because it works with all the other boards and i am able to flash the code.
However with this board, when i power it up the orange led continuously lights up, unlike other boards where the orange led blinked when i first powered it up.

I am have a external power supply for all the boards and i have scrubbed the backside of teensy board so that it only powers up with external source.

Could someone help me understand the problem. Could it be that i destroyed the board when soldering ?
 
@Akram:

Here are a few quick things to try (in this order):

Have you checked for a short on the 3.3VDC power supply as described <here> ??

Have you measured the 3.3VDC supply when plugged into power ??

Did you try the <factory reset> procedure on it ??

Mark J Culross
KD5RXT
 
Hii @kd5rxt-mark
Thank you very much for your reply :))
I checked the short on 3.3VDC power supply and found the resistance between pin10 and 3.3V is 19.90 Kohms.
I measured the 3.3VDC when powered on but i could not see ant voltage there, which is so strange :(
Do you have any idea what could be the problem. Maybe I fried something while soldering ?

Thank you so much in advance for your help.
Akram
 
@Akram: with the resistance value that you measured (a somewhat higher value, rather than a value close to 0 ohms) probably indicates the lack of a dead short, so that seems to be good. However, the fact that you measure no voltage out of the 3.3VDC pin is not a good sign. Do I understand correctly that you have cut the VIN-to-VUSB connection ?? If so, can you temporarily add a jumper to restore that connection & test with your USB cable instead of an external supply ?? If that makes no difference, it really sounds a lot like you may have somehow damaged your 3.3VDC regulator chip, which is usually fatal.

As one final check, look carefully at your Teensy under moderate magnification to make sure that you don't have any shorts (such as an errant solder ball) somewhere on the board. While you are at it, you should also inspect all of the pins that you soldered just to make double sure that you have a good quality solder connection (no cold and/or incomplete solder joints).

Good luck !!

Mark J Culross
KD5RXT
 
Hi @kd5rxt-mark
So now i powered the teensy with USB cable by joining again the pad at the back.
What i observed is now that there is no orange led light coming up unlike before where orange led continuously lighted up.
I measured the voltage in VIN pin and measured 4.9V.
Strangely enough i measured only 0.7 V on 3.3V pin.

I think I somehow have destroyed the 3.3V voltage regulator chip.
Anyways I will order a new one.
Thank you so much for the help
Akram
 
One thing to be careful with when cutting the track is to make sure that you do NOT cut too deep. This is a multi layer (5 I believe) board and it's possible that you have severed tracks underneath the top layer. The track to be cut is on the surface and just needs scoring and lifting off. I know it's difficult, I have done it myself. Best to just do it a little bit at a time until the track is truly cut. Frustrating I know from experience scraping away time after time until YAY it's done! No USB voltage getting through to the rest of the board.
 
5 layer I've not heard of, usually come in pairs, for dense SMT with BGA parts 6 or 8 layers is more likely.
 
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