i am using bayangtoys X16 GPS drone.
I managed to solder the “alfa APA-M04 7 dBi gain RP-SMA directional panel antenna Wi-Fi” on the board, and it was working absolutely fine. Until, I put hot glue on the antenna’s solder to make it more solid.
Since then , when I power on the remote the red light comes on for a second and beeps then it goes off. I removed the hot glue and still its doing same thing…
Have I burnt the Tx?
I have checked for any short on the antenna’s ground and main wire, there is no short there. I have checked the battery and power, and all looks good.
Could anyone help me out please!
Hi, You won’t have burnt the Tx, as the hot melt gun operates around 120C, and all of the components on the PCB’s get soldered at 220C (or higher).
What’s more likely is you have damaged something with ESD, by touching something with the metal nozzle of the glue gun. Most glue guns are double insulated, so there will be some capacitive leakage current due to close proximity of the element and the metal barrel of the glue gun that the element wraps around.
For future reference, the glue gun stays hot for several minutes, so you can unplug it before applying to ESD sensitive parts.
You get similar ESD issues with laptops running off the charger, and connecting up say a micro’s serial port to a USB TTL serial dongle. (Done that about 3 times myself arrrgh!)
I remember the glue gun did not touch anything on the PCB
May I know what could have gone bad?
I am not familiar with the parts you are using, so can only offer general info.
Your symptoms indicate the unit powers up , but doesn’t stay on, so possibly the "power stay on " MOSFET has been damaged by excessive gate-drain voltage.
In general , the low level of leakage current involved in the ESD scenario indicates a possible vulnerable component, and the gate drive for a MOSFET is a likely culprit.
I’ve damaged MOSFET’s on power control circuitry with similar high dV/dT events
The problem isn’t so much a really high voltage (kV level), but a modest voltage (110v = mains midpoint) with a fairly large coupling capacitance (e.g. your human body capacitance and the capacitance of heating element to barrel) .You only need > 20v on the gate-drain to permanently change the gate oxide , and the MOSFET does any number of weird things after that, (most commonly turns into a 2v zener)
You could have damaged any of the parts in that portion of the controller when glueing it with hot glue. As Bob is saying, just touching them with the tip of the hot glue gun could have damaged them. The hot glue gun could have discharged static from the tip, even the smallest jolt where it doesn’t belong can damage sensitive electronics. The difficult thing here is that we don’t have any way of knowing what component might have been damaged. The charge may have carried to another part of the controller entirely.
This will be difficult to troubleshoot without a wiring diagram. I agree with Bob that its most likely the MOSFET that controls the power. It could be any other transistor gone bad as well though.