I’ve had my Avio 3” for almost 2 years and it has a mini 5848 by jmcho that has worked great never overheating but once I switched receivers (I may have gotten it too hot updating ghost in field??).
Now even at 25mW it starts blinking video and leds but once I blow some air over it or fly blind for a few seconds it works great until I land and within seconds it’s overheating again.
  
 I took vtx out of quad for better air flow,used new power wires and direct power from 4S still overheating.

 Could I have cooked a component?

I am not sure if the Ghost receiver will cause the VTX to over heat.

You probably have a cooked component on the VTX. What VTX is this?

You can try and identify that component by touch or by using a thermocouple probe on a multimeter but its hard work. Usual suspects will be the voltage regulator and the amplifier but it can also be the onboard RF chip or perhaps a bad capacitor. (If only there was an affordable thermal camera that could work at a macro/micro level for the size of components on our boards).

(01-Jul-2022, 03:52 AM)kafie1980 Wrote: (If only there was an affordable thermal camera that could work at a macro/micro level for the size of components on our boards).

I remember someone posting a video somewhere on this forum of a guy putting rosin in a vape pen, using that to dust the board, and then watching it under a magnifying glass while it was powered up to see what melted the rosin first.

You can do something similar with Isopropyl alcohol (IPA) in that it evaporates quickly on the components that are heating up faster.

The residue that the Rosin leaves requires cleaning up which is additional work.

These methods are only affective if the temperature contrast is higher at the shorted component compared to the rest of the PCB. Works on larger PCBs as it takes time for the heat to transfer to the rest of the board.

On a small VTX this can be challenging since the entire VTX board heats up very quickly and heat spreads fairly fast.

I think I got something too hot and it weakened it somehow.
I’ll try it again after updating avio 3” to betaflight 4.3 just in case it’s getting into pit mode.
It’s a jhmco mini 5848.
I’ll likely just get another vtx and if I ever get a micro scope to work on these micro electronics maybe I will attempt to diagnose.
Even with a microscope I bet these are tedious to work on.
It’s been a good Vtx and even has a built in micro phone.

I’m going to toss it in the spare parts bin.
It works if I start flying but I don’t want to risk losing a quad so better replace it.
It’s more than one component boiling away alcohol.

This is why I don’t recommend alcohol evaporation or rosin vapour tests on small vtx boards as the entire board heats up pretty quick and its hard to pin point the exact component that failing.

If you have good magnification or even a macro lens on your smartphone, you can try and inspect the board for any visual signs of heat damage, maybe a burned capacitor. Or using a multimeter check the regulator etc.

Another suggestion working on small boards is using needle probe attachments to regular multimeter probes as the components are fairly close and its best avoiding an accidental short.