Order Number: 690437
Product Name: Tunerc Poly F405 2-4s Aio Fc/ Tr-Fc-F005
Brand: TuneRC
After installing the AIO in my Frame and soldering everything to it, i tested via the xt30 with a multimeter to make sure no short circuit and used a vifly shortsaver 2 when powering up for the first time and it powered up ok using a 550mAh 4S battery, i then plugged in the micro usb from my PC to the AIO to connect to BetaFlight and check the motor positions and directions, from plugging in the usb to the AIO i looked up at my PC monitor and notices Smoke coming from the AIO and the shortstopper tripped out, i quickly unplugged the usb and shortstopper from the AIO, looking under my microscope i can see it is the STM32F405 chip that has failed
I’ve checked under my microscope and can see the F405 chip has failed
Hi
From the looks of that, something has shorted and fried your MCU. Could I ask if you checked the FC before you soldered anything to double check it works, as per our suggestion here - How do I test my new Flight Controller? (and why it’s important) (unmannedtech.co.uk)
I have also had a look, and while I cant see all the soldering exactly from the photos, it looks like some of it may be flowing over to other components on the FC which is likely the cause.
You can double check this guide to check your MCU, but from the burn mark, its pretty certain that its been fried 
Hi Alex,
I did plug the AIO into the PC and check it connected to betaflight first.
Sorry for the poor quality photos from my phone, here are photos from my microscope
I have continuity tested the MCU between VCC & VDD and it is short circuit
Thank you for the photos, I will pass this onto the manufacturer, however given that it was working before you soldered something onto the FC, and then it failed after with the MCU being shorted, its likely that this has been caused by a solder splatter or some other short. I will try to discuss and arrange a replacement with the manufacturer and see what we can do, however this kind of fault is usually not a manufacturing defect as it was working for them to flash the bootloader and betaflight onto it in the MCU in the first place…
Kind Regards
Alex
Unmanned Tech
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Hello, it’s been two weeks since the last message, is there any response from the manufacturer?
Thankyou.
Sorry about the delays we have still not had any positive outcome from the manufacturer as they are refusing to issue a replacement under warranty as the issue you experience is caused by the MCU shorting We are trying to work with them to issue a replacement but have not been successful yet.
This is why we ask all our customers to first check their FC for any issues before they solder, as after soldering we find that many manufacturers are not as willing to issue replacements as often its the soldering that causes the issue. As in your case the FC was confirmed to be working before soldering, and then after soldering the MCU is shorted which indicates that after soldering/building an issue has occurred
Kind Regards
Alex
Unmanned Tech Support
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Thankyou, will it help my case if I send the AIO into yourselves to inspect?
Unfortunately not, however, could you double check your MCU with a multimeter as per this guide and let me know the outcome, as this will confirm if the MCU has been shorted or not -
How to check MCU for shorts/continuity and Pinouts for Flight Controller MCU
Kind Regards
Alex
Unmanned Tech Support
Join our community at dronetrest.com, or on Discord.
Yes Vbat and VDD are short circuit on the processor, also the TX4 pad is short to gnd
Hi again,
Unfortunately a shorted MCU like this does indicate that power has made it’s way to the MCU where it shouldn’t, and something has shorted. If it was working prior to install, this would unfortunately indicate an issue with either the soldering or installation of the board.
Is the FC or any solder / wiring from it making any contact with the frame at all?
Best regards,
Cameron
Unmanned Tech
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