External USB&Led adapters not working with pixhawk boards

I have been using pixhawk for six months and I am very satisified with it. External usb&led adapter is a good option to download the dflogs from the plane because its not possible to reach the side usb port of pixhawk in the fuselage.
Last week I bought 3 new pixhawk boards from a reliable chinese vendor and 5 led&usb adapters but I could not make a connection between the boards using external adapters. When I connect it powers the board, pixhawk starts but no light on the external led and pc does not recognize the pixhawk itself via usb.
When I use the default usb port (side) pc recognizes the pixhawk.
First, I thought that one of the boards or adapters was broken but what is the possibility of 3 broken boards or 5 broken usb&led adapters at the same time?
Do you have any idea about what has been changed because I was able to use the led&usb adapter on my previous plane with another pixhawk from the same vendor?
Thank you.

@Onur BOY,

I found that the wires on the external USB connector are so small that the voltage drop between the USB connector and the Pixhawk will reduce the voltage being sent to the Pixhawk to below 4.5 vdc which will result in the Pixhawk not booting up.

Using the 3DR external USB connector I have been able to get the Pixhawk to boot up, but the attached PPM Encoder does not work due to the excessive voltage drop.