Successful repair of a 2.8 controller board including replacing the Mega IC and installing the bootloader again

In short, even though the component damage were extensive, the repairs worked. I share this experience should anyone else be in the same position of having a damaged board and wonder if it can be or has been, done.

We have just done some serious repairs to the controller board after an incident involving a small bit of water on the board along the top edge, resulting in blown 12v-5v-3v regulators and a number of other components, as the initial damage seems to have rippled downstream through the board.

Having a dead board, the first diagnostics tests showed a problem with power distribution, 12v coming in, but no 5v or 3v available, which we fixed that by changing out the relevant components, only to then reveal further problems down stream, right back to the Mega and after e.g. gates to the ESC power control and onboard lights.

As well as the Mega IC on the controller board, changed out the shifters and some other components, including 12-5v and 5-3v regulators as noted above. As the new Mega was blank, used the 30.0.3 ROV SD image in the ROV to boot up and using SSH to get to the script, did a chmod +x and ran it with sudo. Happy to see this message:

v30.0.3 was the last build I could see with a script with AVRDUDE parameters for the bootloader, anyway it woke up the Mega, so powered down and put in the SD with the 31 RC7 image and powered up again. That version installed the firmware to the CB and was happy to say ended up with a working ROV with HD video again, controllable with the gamepad.

Tip 1: used 7-Zip File Manager to poke round in each of the downloaded images first under Windows, without having to burn the image to a SD card, run on the BB and access via SSH, like looking for the burn-bootloader script or something similar, after unsuccessfully trying to track it down on GitHub.

The components came off pretty easy, pads and traces all good and cleaned up well, and with the aid the stereo microscope got the IC and other components installed squarely on traces and pads and then reflowed to solder in the SMD’s.

Tip 2: I was happy to do the diagnostics and sw side, I used a company with plenty of experience in doing SMD repairs and having all the right tools, my field tool box not being appropriate !

My impression is this shows the benefits of open source with good documentation and that the controller board were well built, pretty robust (withstanding heating during repairs) and can be brought back with a bit of effort.

I am interested to hear about any repairs that others have done, other tips and in general what other OpenROV users are doing on the subject of a major spares or lack of. I am thinking of running up a few boards for the CB and IMU and populating over the winter after this experience, keeping OpenROV’s alive and exploring :smile: