Electronics > Beginners

Pulling my hair out. Circuit boards stop working once shipped to client and more

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daqq:
One of the issues we've had were crystal load capacitors - in the prototype everything worked. After a batch was made, quite a lot didn't work. This was because the load capacitance was above the one specified by the processor (STM32L1). The oscillator simply wouldn't start. We had to replace all of the capacitors.

Jackster:
So I managed to get some time in the office today and got one of the bad boards and started removing components and testing.

After a few, I removed the FTDI and it burned the boot loader.
Put all the other components back other than the FTDI and again it burned.

I then put the same FTDI chip back and it did not burn. Removed it and it burned.
I then got a known working FTDI chip from RS and it burnt the boot loader.

I need to double check all of this in the morning so this is more of a note for myself.
The LCSC ones are dated year 17 and the RS ones are dates 18.

Will take a working board and remove the working FTDI chip and replace with one of the new FTDI chips and see if it burns the boot loader in the morning.

mcinque:
If I may, I will invest time in understanding WHAT is failed instead trying to fix something that you don't know exactly.

HantekDSO5102P is fine, you could choose also a Siglent SDS1052DL or a used classic Rigol DS1052E.
I know that you should learn how to use it properly but it's something mandatory and not so difficoult (if I can use it , anyone else can do). You can't live without it.

Once you have an oscilloscope, you can't (and you wouldn't) get back!

Imagine this: without that instrument you are blind.

Jackster:

--- Quote from: mcinque on June 07, 2019, 10:13:54 am ---If I may, I will invest time in understanding WHAT is failed instead trying to fix something that you don't know exactly.

HantekDSO5102P is fine, you could choose also a Siglent SDS1052DL or a used classic Rigol DS1052E.
I know that you should learn how to use it properly but it's something mandatory and not so difficoult (if I can use it , anyone else can do). You can't live without it.

Once you have an oscilloscope, you can't (and you wouldn't) get back!

Imagine this: without that instrument you are blind.

--- End quote ---

IDK what I am looking for though with it.

Ian.M:

--- Quote from: Jackster on June 06, 2019, 11:32:48 pm ---So I managed to get some time in the office today and got one of the bad boards and started removing components and testing.

After a few, I removed the FTDI and it burned the boot loader.
Put all the other components back other than the FTDI and again it burned.

I then put the same FTDI chip back and it did not burn. Removed it and it burned.
I then got a known working FTDI chip from RS and it burnt the boot loader.

I need to double check all of this in the morning so this is more of a note for myself.
The LCSC ones are dated year 17 and the RS ones are dates 18.

Will take a working board and remove the working FTDI chip and replace with one of the new FTDI chips and see if it burns the boot loader in the morning.

--- End quote ---

Possible fake FTDI chips?  Hack a bad board to loop the FDTI's RX and TX pins, open the USB serial port with a terminal program and see if it responds
--- Code: ---NON GENUINE DEVICE FOUND!
--- End code ---
character by character as you type instead of the loopback echoing what you type.  (see: https://www.eevblog.com/forum/microcontrollers/ftdi-gate-2-0/ )

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