Pinecil Broken?
#1
Hello, juste received my pencil (and 2 other for family and friends) yesterday.

Mine worked on a laptop power supply (19V) no problem.



I try it on a usb power bank didn't know if qc3 or something else hit + button.

It seems to heat then a messsage that says low voltage or something, I removed the usb cable.

And back to 19V, nothing on screen. After didassembly I check 3v3, it was 0.7V and it draw 80ma when on 19V.

5v is 4.2v like in the schematics, so I desolder the 3v3 voltage regulator and it draw 2ma.

check continuity betwen 3v3 and gnd and got 5ohms not good, I replace the voltage regulator by a generic LD1117 3.3v.


here the grotesque picture.


[Image: 1S2-MfsJ1bWqdHaFkLEPkdNFBLiM7zQc5?e=down...5jusharing]


And its back to life sort of, it draw 200ma when idle the other are around 10ma. and the U1 chip FUSB302MPX is extremely hot.
the 3.3V is at 3V and it show 21 V instead of 19 it look "normal" considering the voltage divider.
my next step is to desolder the U1 and check for continuity between 3v3 and gnd but it have to wait until I can get to an air desolder station.

I will tell you that you should'nt try to make it work on 5V, I did it itentionaly but it can happen accidentaly.
I think as it know the voltage some sort of software protection could be implemented to avoid this.
Or I get a bad one, you tell me.

Thanks for reading.

The other 2 are working good.
  Reply
#2
(12-29-2020, 01:11 PM)skaaq Wrote: I will tell you that you should'nt try to make it work on 5V, I did it itentionaly but it can happen accidentaly.
I think as it know the voltage some sort of software protection could be implemented to avoid this.
Or I get a bad one, you tell me.

I don't know what happened with yours.
I have also bought three, one for my family member, one for my friend and one for myself, but so far only one has arrived, others are going to arrive in a few days.

However, I have tried different Type-C power supplies on this one, also a 20V capable one and a power bank, and also a regular 5V charger.
It worked with all of them, but the power bank was only able to go up to 9V and I have only experienced low voltage warning when I have connected to a regular 5V supply which is as expected.
...but it is still working, I don't think regular 5V should cause any problems.

It may had some faulty component(s) or maybe your power bank could make a voltage spike which caused the internal circuit to burn out.
I have read there was a protection diode which is not applied on production devices and absolute maximum rating of a component is 24V, so a voltage spike may cause problems.

However, FUSB302 has an absolute maximum rating for VVBUS voltage as 28V and recommended operating voltage of 21V and the IC may be the source of the problem you have... I think.
  Reply
#3
The picture that didn't upload correctly

[Image: thumbnail?authuser=0&sz=w640&id=1S2-MfsJ...FBLiM7zQc5]

So I remove the FUSB302MPX with hot air station, before that I removed every solder I can with solder wick.

[Image: thumbnail?authuser=0&sz=w640&id=15Rt-rwB...fPkmOwRBZt]

I think it was glued to the pcb so it was difficult to remove, I had to melt it basically. It turn ok after cleaning

After that no more "shortcut" between 3v3 and gnd.

I salvage the 3v3 regulator from the breakout board and solder it on the pinecil.

Now It work like the other, same current 10-20 mA when idle, same voltage on screen.
I can plug usb, but I will use it with barrel jack for the moment.

I will try to solder back a new fusb and other regulator if I can find one.
Still I do not know what happened, if 3v3 failed it should have fried the microcontroller and the bma223 but both are working.
best bet is a bad FUSB from beginning.
  Reply
#4
(12-31-2020, 03:34 AM)skaaq Wrote: I will try to solder back a new fusb and other regulator if I can find one.
Still I do not know what happened, if 3v3 failed it should have fried the microcontroller and the bma223 but both are working.
best bet is a bad FUSB from beginning.

FUSB is around 1 EUR at Farnell / Mouser (plus shipping for sure), I think the regulator will also have a similar price.
Resoldering of this package by hand is possible, so I hope you will be able to repair it.
  Reply
#5
I bought the fusb on LCSC for less, and now it work as it should. I confirm that powering the solder with 5V will not do any harm. I must have a bad fusb from begining.
  Reply


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