Order #UT-729222-WH/OUT/55721) - Fl85-O4p-Wtfpv - Faulty FC on Flylens 85

Help Unmanned Tech
1

Order Number: UT-729222-WH/OUT/55721)
Product Name: Fl85-O4p-Wtfpv
Brand: Flywoo
The aircraft does not boot up anymore after plugging the LiPO in. The O4 is still powered, but peripherals (Crossfire RX) are not - the FC hangs with a solid orange light. Plugging the FC into USB works.

After a few flights, it seems the capacitor has worked its way loose, and the lead may have shorted across the VBAT terminals. I suspect this could have killed the 3.3 or 4.5V regulator on the FC.

  • I have taken the aircraft apart and can observe the capacitor has detached from the power leads
  • I have plugged FC into USB, and I can confirm it powers on
  • The FC still powers the O4 air unit when the LiPo is plugged in, so the 9V regulator must still be functional
  • When powering the aircraft via LiPo, the Crossfire RX attached to the 4.5V rail does not power on

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2

Hi,

That sounds like a frustrating problem, but your analysis looks precise based on the symptoms you’ve described.

Here’s a breakdown matching your observations:

  1. Works on USB: Confirms the MCU itself and the USB-powered 3.3V circuitry are likely okay.
  2. O4 Powers On (LiPo): Shows VBAT is getting to the board and the high-voltage rail for the O4 (likely 9V BEC or VBAT passthrough) is functional.
  3. Crossfire RX Dead (LiPo): This is the key. Since the RX runs off the 4.5V rail provided by the FC, and it only fails when powered by LiPo, it strongly points to the 4.5V/5V voltage regulator on the FC being damaged. This regulator takes VBAT from the LiPo and steps it down.
  4. Solid Orange Light (LiPo): Consistent with the FC failing to boot fully, likely because essential components (potentially including the 3.3V rail derived from the now-dead 5V rail) aren’t receiving power when the LiPo is the source.
  5. Capacitor Short: Absolutely the prime suspect for causing the regulator failure. Shorting VBAT can easily overload and destroy sensitive regulator ICs.

It’s highly probable that the 4.5V/5V regulator on your Flywoo FC is dead.

What Next?

  • Visual Inspection: Carefully examine the FC board, especially around the voltage regulator ICs (small black chips near the power input or 4.5V/5V pads), looking for any burn marks or physical damage.
  • Repair (Difficult): Replacing surface-mount voltage regulators requires micro-soldering skills and identifying the exact replacement part. It can be done but isn’t easy on these dense AIO boards.
  • FC Replacement: Unfortunately, this is often the most practical solution for a blown onboard regulator unless you’re equipped for micro-soldering.

It seems your diagnosis was correct – the capacitor short likely killed the regulator. Sorry to hear about the hardware failure! We will reach out to Flywoo support, but physical damage from a short is not typically something they cover under warranty.

3

Hi and thanks for the quick reply. We are in agreement with the diagnosis.

I’ve managed a ‘fix’ by backpowering the 5V rail with a small BEC that I had lying around: Matek Micro BEC 6-30V 5V/9V Adjustable (3pcs) – Unmanned Tech Shop

This means the 3.3V regulator is alive and the fault has only damaged the 5V regulator.

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The FC now works, and this seems to be a viable fix for anyone with the same issue. The TPU bracket for holding the RX/LED BEC can be modified to hold this BEC if the LEDs are deleted from the drone.

Understandable about the warranty - however my feedback to Flywoo would be to have a bit of strain relief on the capacitor leads such as a dab of hot glue/E6000. Let me know how it goes and have a good Easter break!

4

Hi good day,

I know you have soldered together a work around for your AIO, but I did not think it was fair that you should have had to do this in the first place, as it looked like a genuine soldering fault from the factory. Flywoo make really good products and their QC is impeccable, but with everything in life, nothing is perfect.

I explainded to Flywoo that I felt this was a factory fault and I could not see anything wrong with your drone, it doesn’t look like it has been mistreated or crashed, Flywoo agreed and I manged to get them to agree to a replacement board for you.

So, long story short, I can offer you a brand new replacement or a refund for the board.

Let me know which you would prefer and I can action that for you?

I hope this helps and happy flying.

Regards,
David

Unmanned Tech Support

5

Hi David,

Thanks for the escalation, and I’m very happy with Flywoo’s response. The Flylens otherwise is a great little aircraft, and just a little bit of reinforcement on the capacitor legs for future production runs will likely fix this for them.

Since the aircraft is now working with the BEC fix and I’ve been a longtime UMT customer - some store credit to the value of the FC would be the best solution.

All the best,
Chen