I am building a new quad and put a new 4in1 on it. I wanted to use one of my old FC's.  I can put the old FC on my existing drone and plug in a battery and I get all 5 tones, lights on my FC and I can use my multimeter to verify I have 5v or so across the 5v terminals.  When I put the same FC on my new quad, I only get 3 tones and no lights on the board but oddly I get my VTX powered up which is connected to the VBAT pad on my FC.  When I plug in FC to USB, I then get the lights on my FC but still no communication to the 4in1 inside of Betaflgiht. 

I had to repin the jst connector and I assume I messed something up since the board works fine on one 4in1 but not on the other. The weird thing is that my VTX gets power on both but nothing else seems to be working when connected to the new 4in1. The FC has a pin for 5v and the old 4in1 has a 5v going into it. The new 4in1 does not have a 5v pin but I was told this is ok.  

Can anyone help me understand why I don't get power to all of my FC with my new 4in1.

Flight controller xrotor Micro F4 g3

4in1: SucceX-E 45A 2-6S BLHeli_S Dshot600 4-in-1 ESC

Thanks

The problem you have is that the Hobbywing XRotor Micro F4 G3 FC doesn't have an onboard 5V BEC so it needs a 5V supply from the ESC (on pin #5 of the ESC socket of the FC), but the iFlight SucceX-E ESC doesn't have an onboard 5V BEC either and therefore isn't supplying the FC with the 5V that it needs via it's ESC-to-FC connector. The ESC on your other quad would have been supplying 5V to the FC on pin #5 of the ESC socket.

Your only real option with the FC and ESC you currently have is to get an external 5V BEC and wire it up to one of the 5V pads on the FC so that it will inject the required 5V supply.

That is super smart and really helpful.  So if I understand you correctly, I need something like this https://shop.iflight-rc.com/micro-2-8s-b...put-pro747


I would follow the 5v pattern by connecting the vbat directly to the battery and then I would solder to one of my 5v and to one of my ground.  Correct? Would I only need one for the whole board?

Also, would that solve my connection to the motors problems?  Even when connected to USB, I don't get the 4th and 5th tones when connecting a battery and I can't spin the motors in betaflight.

Thanks so much.

Yes, that iFlight BEC is perfectly fine. It can supply up to 3A of current when in 5V output mode which will be more than sufficient for your FC and any external 5V peripherals that you connect to it.

Just wire it up as you specified:-

• IN (5-36V) -> VBAT+ pad on the FC
  
• GND (either pad, it doesn't matter which) -> GND pad on the FC
  
• OUT (5V/12V) -> 5V pad on the FC
  

Make sure the 12V output selection pads on the BEC aren't NOT bridged so you get 5V coming out of the BEC.

I will order that BEC and hope it fixes my motor connection problem too. Thank