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!