Reload-pro repair information and example provided in this issue.

[royfranz]

Not really an issue, I'm using this to present what I learned from repairing mine, and to post some files that Nick provided that were helpful.

Recently my Reload:pro failed when I hooked it up to an 18v battery, and I have no idea what cause this. I did see some strange behavior as I was setting it up, as it would be detected and then disconnect over USB on my computer, and I could only get it work on certain ports. I think this may be related to the large current draw that I only noticed after the failure.

After the failure, the unit was completely dead, and would not turn on. On my second inspection, I found that the sense resistor had visible damage - it let the smoke out on the underside. While debugging it I found that it was drawing a lot of current over the USB, enough to get the 5v dc-dc converter used for isolation to smoke. After removing a few of the smaller components, it looked like the MCU was causing the short. It also looked like the main load FET and one of the protection diodes was also damaged.

I replaced the following parts:

• MCU
• Main load FET (maybe not direct replacement, see issue below)
• sense resistor
• protection diodes
• zener diode on DC/DC converter (I don't think this was damaged, but I had removed it while debugging the power/ground short and replaced it with a new one while I was at it.
• DC/DC converter
  (I ordered but did not use the opto-isolator chip, as the serial communication worked after I replaced the MCU.)
  (compatible displays are also still readily available for about $15 - I ended up getting one due to installing the old 0.11 firmware by accident and the display not working with that.)

I used the CY8CKIT-059 to reprogram the new MCU in circuit, using the 1.10 hex files from github. This was quite easy to do after installing the rather large software package (Windows required.) I simply programmed the bootloader hex and then the firmware hex.

After this my reload pro is now working again, but there are a couple of issues to be aware of:

• I was unable to build the firmware with the latest code - I got an error of being out of ROM space and other size violations. I am running the 1.10 code, which is the latest hex file in github, but not the latest code overall.
• When calibrating, the unit wanted to draw 4 amps instead of 2 as described in the manual. Calibration will not work unless you can meet this current draw at a reasonable voltage. If you calibrate it with a current limiting PS that is at its current limit and very low voltage, the calibration will be way off. It took me several tries to get it calibrated properly due to this. I don't know why this is - my guess is that it could be due to the load FET being not quite what is expected, and that fixed control levels are used during calibration that cause this to be off. (Edit - I just took the unit out to test again, and now the current is off by a factor of 2. I re-did the calibration, and this time it drew the expected 2 amps, and now it is reading correctly again. I don't know what to make of this, but am sure about the 4A current draw, as I was hitting the 3 amp limit during calibration on my bench power supply the first time around.)

Here is the BOM, schematic, and dch/dip (layout?) files that Nick provided to help me debug it - thank you Nick for your help getting my Reload:pro fixed! I have also included an image of my digikey order.

Reload Pro Schematic.pdf

reload-pro-dch-dip.zip