So you think you broke your discovery, good news, we have some tips for diagnostics and some suggestions for solutions. Fear not there is likely some good news below. For this diagnostics, we will assume you have removed the discovery from what ever circuit it was connected to and it is only being connected via "CN1" USB jack on SWD side of the board. The board should be something like the below picture.
This prevents the 3V from making it to the target ST chip. This will isolate the part of the board you may have damaged. It will likely remove stray loads and will allow you to test if the power supply and SWD programming chip is functional.
#### Check(s) to determine what solution to follow
* Does the red LD2 "PWR" go bright RED? -- If so your power supply is probably in good order. Go to solution **Step 2**. If the LED is dim, proceed to the next line.
* Is LD1 "COM" solid red and LD2 "PWR" dim? -- If so this is good, it means you are getting 5V via USB and the programmer chip is probably functional. If it is red, proceed to **Solution 1 Broken D3** else proceed to the next line.
* Is LD1 "COM" green? -- If so this means you have 3V and ??? (I don't know when it will be green). If it's green or blinks green when communicating with it, this means you have 3V and your LD2 "PWR" light is broken. Proceed to **Solution 3 Broken LD1** else proceed to the next line.
* Is LD1 "COM" blinking red? -- If so this could be and could be indicating the processor is active and doing stuff. TBD inquire in the forums for help.
* Are all LED's off? -- If so this likely means there was a 5V short to GND and D1 has broken. To really check, with a multi-meter measure  DC voltage referenced to GND like at JP2 or JP3. Measure the voltage at both sides of D1. If you measure 5V at one side and less than 100mV on the other side, proceed to **Solution 2 Broken D1** If you measure below 100mV on both sides, 5V is not making it to this board, check your USB is providing 5V.
reference forum suggestion for repair found here [stm32f4discovery troubleshooting and repair - Forum](http://rusefi.com/forum/viewtopic.php?f=4&t=653&start=16)
You may notice that D1, D2, D3 are the same. You probably don't use D2, as R2 is not populated by default. You can probably safely re-purpose that diode. If you have a second broken board, you can probably scavenge a diode from another dead board. If replace the diode, before you power it up, carefully check that the line on the diode looks like it does in the picture. If it's installed backwards, the board will not turn on. It will act like the diode is broken. Once this repair has been made, start the diagnostics process over.
Easiest solution is to get a new D3 which can be found [here at digikey](http://www.digikey.com/product-detail/en/BAT60JFILM/497-3707-6-ND/1848703?WT.z_cid=ref_octopart_dkc_buynow&site=us) or [here at octopart](http://octopart.com/partsearch#!?q=BAT60JFILM%0D%0A)
If you replace the diode, before you power it up, carefully check that the line on the diode looks like it does in the picture. If it's installed backwards, the board will not turn on. It will act like the diode is broken. Once this repair has been made, start the diagnostics process over.
You can remove the diode and install a little jumper wire. However be careful as a short to GND now could damage your regulator, and it's much harder to replace the regulator. Once this repair has been made, start the diagnostics process over.
the measured ohms (auto scale) to GND with JP1 removed, The SWD side of JP1 measured at 7.34k ohms, and the audio jack side of JP 1 measured at 4.98k ohms.
