computer does not see board anymore

Hi all. I have this sainsmart 3 in 1 arduino bard for a 3D printer. It died when I put in a stepstick driver that was apparently bad. I figured there was one bad one in the batch so I tried them one by one. One motor attached.

I unplugged power from the board and put in a step stick. If the motor powered up and held its position it was ok. I went through my step sticks in this way. I unplugged between each swapout. With one stepstick, all the lights on the board came on then they all went out.

Since then I have been unable to communicate with the board. Not with a windows box or osx It does not show up in device manager or in device details about this MAC.

Is there hope for getting this board up again? What are my first steps to troubleshoot what's wrong? I do have the equipment and know how to replace some of the components.

Jonathan

Sounds like the stepstick was defective in a way that damaged the board.

Most likely, an excessive voltage got onto Vcc and damaged the USB serial interface IC - some clone boards will tolerate this briefly; official boards rarely do (the 16u2 seems very vulnerable to this sort of abuse)

Any case where a device is getting external power, I'd measure the voltages they're outputting on the pins before connecting to another board - at least if there's any question about their condition.

So you are saying it's likely the USB serial interface? I would guess that means there is little hope for the board?

The USB serial interface IC on this board is a ft232rl. I see they are very common on arduino programmers. like this one.

Sorry for the long link. I don't remember how to shorten it. Would it work to replace that serial interface? Perhaps using one off a board like that? A quick search hasn't shown me where I can buy the IC only.

Jonathan

E-bay is crap for ICs.
Use a real distributor like Digikey or Mouser
https://www.digikey.com/product-detail/en/ftdi-future-technology-devices-international-ltd/FT232RL-REEL/768-1007-1-ND/1836402
https://www.mouser.com/ProductDetail/FTDI/FT232RL-REEL/?qs=sGAEpiMZZMtv%2bwxsgy%2FhiB6Z76KqffMClqcDgIugTZc%3D
They have been $4.50 a chip for as long as I have been buying them, going back to 2011.