Main board doesn't boot completely

[cabinfourus]

When I purchased some parts from a local repair shop, I found a lot of the H Plus and H520 main boards, in the deal. You can tell they had been involved in a crash, since a few of the LED connectors had been ripped from the boards. After replacing the SMD connectors, I decided to try one of the H520 boards. So, I installed this board in one of my H520 birds, and tried to power it up. Pressing the power button causes the drone to try and boot, but it doesn't seem to complete the boot process. On the board, you can see three blue LEDs that light up, while the board tries to boot. I can hold the power button, and the E90 camera will boot up without an issue, and the main board's LEDs stay lit. I read in a prior post on here, where someone had this exact problem, and it turned out to be a "bricked main board". The owner sent it to a repair shop, they re-flashed the firmware, and all was good to go. I am not sure how exactly the repair shop was able to flash his FW, without the drone booting completely.

My dilemma is that no one carries this board anymore. So I must either fix the current board or toss it, and hope one shows up on eBay one day. I am a huge pack rat, when it comes to drones, and I really don't like throwing anything away. Sometimes I can use parts from old boards or use them for diagnostics. I am sure most of you, are doing the same, since Yuneec left us high and dry.

My questions are-
1. Have any of you seen or repaired an H520 or H Plus with this type of behavior?
2. Does this sound firmware related? Bad flash?
3. Being these boards were involved in crashes, do you think it could be a chip or circuit failure due to the hard impact?
I am looking for a good place to start with my repair of the board. I wouldn't mind buying another board, if anyone has one for sale or trade.

Lastly, I know you all have read my posts about our coming travels. Well, after many months of delays, and a lot of money spent, I can finally say we are heading out tomorrow. This will be the first leg of our trip, and it is for 35–40 days. We are going to be heading to Charleston, SC tomorrow, unless the storm becomes a major threat. If so, we will have to reroute our trip to avoid the danger. We plan to travel up the coast into Virginia, before returning home for the holidays. We decided to do a short trip first, to weed out any small issues we may encounter, and get an idea of how this will all workout. My wife and I are super excited about this trip, and I will be posting videos to my YouTube page, if anyone is interested in following us on our journey. This doesn't mean, I won't be working with my babies (drones). It just means I will be doing it at campgrounds.

I hope and pray you all have a wonderful and blessed day today.

 

[DoomMeister]

Your issue with the H520 board sounds like the latching circuitry is not working. I had an issue with an H480 that was just the opposite where once booted the battery had to be pulled to power down. I had to manually trace the circuit paths and found a 4.7K SMD resistor was open.

I have block diagrams of the F/C for the H480 which told me which lines to/from the F/C deal with the power on/off circuits.

I do not know of any for the H520 unless @Enrico Jorysch or @Stephen1988 may have access to that information.

 

[h-elsner]

The STM32 do not need to fully boot up to flash the FW. During boot it comes to a point where the bootloader decides to go into flash mode or continues the boot process until the user programm loop is started. At this point the power latch will locked.

There is a good chance to reflash the FW if the bootloader works. Do you have the flash tool "FC_upgrade_tool_win.exe"? First start the flash process in the tool and then power on the board to make the bootloader coming up.

 

[Stephen1988]

Your issue with the H520 board sounds like the latching circuitry is not working. I had an issue with an H480 that was just the opposite where once booted the battery had to be pulled to power down. I had to manually trace the circuit paths and found a 4.7K SMD resistor was open.

I have block diagrams of the F/C for the H480 which told me which lines to/from the F/C deal with the power on/off circuits.

I do not know of any for the H520 unless @Enrico Jorysch or @Stephen1988 may have access to that information.

What diagram do u require, something for h520 mainboard

 

[DoomMeister]

What diagram do u require, something for h520 mainboard

Yes, schematics or block diagram with pinouts for signals to/from the F/C for the H520.

This would be nice for any of Yuneec’s drone aircraft and controllers.

 

[cabinfourus]

Your issue with the H520 board sounds like the latching circuitry is not working. I had an issue with an H480 that was just the opposite where once booted the battery had to be pulled to power down. I had to manually trace the circuit paths and found a 4.7K SMD resistor was open.

I have block diagrams of the F/C for the H480 which told me which lines to/from the F/C deal with the power on/off circuits.

I do not know of any for the H520 unless @Enrico Jorysch or @Stephen1988 may have access to that information.

Thanks for this info. Hopefully someone will have the circuit layouts.

 

[cabinfourus]

What diagram do u require, something for h520 mainboard

I would need the circuit diagram for the board.

 

[h-elsner]

I can olnly help with the debug port of the STM32 flight controller CPU.

 

[h-elsner]

On the board, you can see three blue LEDs that light up, while the board tries to boot.

Btw., you should see six blue LEDs light up when you press the power button. One for each ESC. They should light up also if the processor is not working at all.

 

[cabinfourus]

I can olnly help with the debug port of the STM32 flight controller CPU.

View attachment 32722

This will definitely help! Thank you.

I do see the six blue lights coming on, when I press the power button. I plan to diagnosis it more, when we return home from this trip.

 

[cabinfourus]

It would be nice to have a complete diagram. I am not sure whether I can do it without one.
I have two brand new H Plust boards. I may use one of these in it, and if I can, convert it to be used as an H520.

 

[cabinfourus]

The STM32 do not need to fully boot up to flash the FW. During boot it comes to a point where the bootloader decides to go into flash mode or continues the boot process until the user programm loop is started. At this point the power latch will locked.

There is a good chance to reflash the FW if the bootloader works. Do you have the flash tool "FC_upgrade_tool_win.exe"? First start the flash process in the tool and then power on the board to make the bootloader coming up.

I will try this tonight.

 

[cabinfourus]

With the three boards being nearly identical, is it possible to flash the firmware for the H520 to an H Plus board? Has anyone tried this?
I have two brand new H Plus boards, and was thinking of trying it.

 

[cabinfourus]

So, I wanted to update this thread in case anyone else runs into this problem.

The H520 Main board MUST have the SD card installed, for it to power up correctly. Otherwise, it will power on for a few seconds and shutoff. I used an old 8 GB SD card I had in a drawer, and it worked fine.

Now, it powers up great, but will not power down unless I pull the battery.
Any ideas?